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Showing papers by "Gaurav Sharma published in 2007"


Journal ArticleDOI
TL;DR: The nature of delay-capacity trade-off is related to the nature of node motion, thereby providing a better understanding of the delay- capacity relationship in ad hoc networks in comparison to earlier works.
Abstract: Since the original work of Grossglauser and Tse, which showed that mobility can increase the capacity of an ad hoc network, there has been a lot of interest in characterizing the delay-capacity relationship in ad hoc networks. Various mobility models have been studied in the literature, and the delay-capacity relationships under those models have been characterized. The results indicate that there are trade-offs between the delay and capacity, and that the nature of these trade-offs is strongly influenced by the choice of the mobility model. Some questions that arise are: (i) How representative are these mobility models studied in the literature? (ii) Can the delay-capacity relationship be significantly different under some other "reasonable" mobility model? (iii) What sort of delay-capacity trade-off are we likely to see in a real world scenario? In this paper, we take the first step toward answering some of these questions. In particular, we analyze, among others, the mobility models studied in recent related works, under a unified framework. We relate the nature of delay-capacity trade-off to the nature of node motion, thereby providing a better understanding of the delay-capacity relationship in ad hoc networks in comparison to earlier works.

344 citations


Journal ArticleDOI
TL;DR: Probabilistic analysis can be utilized in order to automate the determination of alignment constraints for pairwise RNA structure prediction methods in a principled fashion and reduce the computational and memory requirements of these methods while maintaining or improving their accuracy of structural prediction.
Abstract: Joint alignment and secondary structure prediction of two RNA sequences can significantly improve the accuracy of the structural predictions. Methods addressing this problem, however, are forced to employ constraints that reduce computation by restricting the alignments and/or structures (i.e. folds) that are permissible. In this paper, a new methodology is presented for the purpose of establishing alignment constraints based on nucleotide alignment and insertion posterior probabilities. Using a hidden Markov model, posterior probabilities of alignment and insertion are computed for all possible pairings of nucleotide positions from the two sequences. These alignment and insertion posterior probabilities are additively combined to obtain probabilities of co-incidence for nucleotide position pairs. A suitable alignment constraint is obtained by thresholding the co-incidence probabilities. The constraint is integrated with Dynalign, a free energy minimization algorithm for joint alignment and secondary structure prediction. The resulting method is benchmarked against the previous version of Dynalign and against other programs for pairwise RNA structure prediction. The proposed technique eliminates manual parameter selection in Dynalign and provides significant computational time savings in comparison to prior constraints in Dynalign while simultaneously providing a small improvement in the structural prediction accuracy. Savings are also realized in memory. In experiments over a 5S RNA dataset with average sequence length of approximately 120 nucleotides, the method reduces computation by a factor of 2. The method performs favorably in comparison to other programs for pairwise RNA structure prediction: yielding better accuracy, on average, and requiring significantly lesser computational resources. Probabilistic analysis can be utilized in order to automate the determination of alignment constraints for pairwise RNA structure prediction methods in a principled fashion. These constraints can reduce the computational and memory requirements of these methods while maintaining or improving their accuracy of structural prediction. This extends the practical reach of these methods to longer length sequences. The revised Dynalign code is freely available for download.

118 citations


Proceedings ArticleDOI
01 May 2007
TL;DR: Two novel randomized distributed algorithms for implementing the maximal scheduling policy under the 1-hop and 2-hop interference models are proposed.
Abstract: We consider the problem of throughput-optimal cross-layer design of wireless networks. We propose a joint congestion control and scheduling algorithm that achieves a fraction 1/dI(G) of the capacity region, where dI(G) depends on certain structural properties of the underlying connectivity graph G of the wireless network and also on the type of interference constraints. For a wide range of wireless networks, dI(G) can be upper bounded by a constant, independent of the number of nodes in the network. The scheduling element of our algorithm is the maximal scheduling policy. Although maximal scheduling policy has been considered in many of the previous works, the difficulties that arise in implementing it in a distributed fashion in the presence of interference have not been dealt with previously. In this paper, we propose two novel randomized distributed algorithms for implementing the maximal scheduling policy under the 1-hop and 2-hop interference models.

74 citations


Journal ArticleDOI
TL;DR: In this article, perchloric acid adsorbed on silica gel (HClO4-SiO2) was used as a highly efficient, inexpensive and reusable catalyst for chemoselective carbon-sulfur bond formation by conjugate addition of thiols to α,β-unsaturated ketones under solvent-free conditions and at rt are reported.

69 citations


Journal ArticleDOI
TL;DR: In this article, ternary FeCo-Ni nanowires are fabricated within the nanoscale pores of alumina membranes using an electrodeposition frequency of 1,000 Hz, 15 Vrms, consistently and repeatably yield nanowire arrays over membranes several cm2 in extent.
Abstract: Deposition into nanoporous alumina membranes is widely used for nanowire fabrication. Herein using AC electrodeposition ternary Fe–Co–Ni nanowires are fabricated within the nanoscale-pores of alumina membranes. Using an electrodeposition frequency of 1,000 Hz, 15 Vrms, consistently and repeatably yield nanowire arrays over membranes several cm2 in extent. Electrochemical Impedance Spectroscopy (EIS) is used to explain the effects of AC electrodeposition frequency. The impedance of the residual alumina barrier layer, separating the underlying aluminum metal and the nanoporous membrane, decreases drastically with electrodeposition frequency facilitating uniform pore-filling of samples several cm2 in area. Anodic polarization studies on thin films having alloy compositions identical to the nanowires display excellent corrosion resistance properties.

63 citations


Journal ArticleDOI
TL;DR: The ability of HDM to accurately and reproducibly measure displacement and regional function in the beating heart and the repeatability of using this method to compute RSW was assessed.

47 citations


Journal ArticleDOI
TL;DR: In this article, the authors reported that the reaction of aryl and alkyl thiols with cyclic/acyclic α,β-unsaturated ketones/ester afforded excellent yields after 5 min to 20 h.
Abstract: Montmorillonite clays are reported as efficient, inexpensive, and reusable catalysts for carbon–sulfur bond formation by conjugate addition of thiols to α,β-unsaturated ketones/ester/nitrile. The reaction of aryl and aryl alkyl thiols with cyclic/acyclic α,β-unsaturated ketones/ester afforded excellent yields after 5 min to 20 h. The reaction rate was found to be influenced by the (i) size of the ring in case of cyclic enone, (ii) electronic nature of the thiol, and (iii) presence of aryl/alkyl substituent at the β position of the acyclic α,β-unsaturated ketone/nitrile. The conjugate addition of thiols took place at faster rates for five-membered and acyclic α,β-unsaturated ketones than the six-membered analogue. Aryl thiols reacted at faster rates than aryl alkyl and alkane thiols and the differential reaction rates were attributed to the relative acidic strength of the thiols. The reaction of α,β-unsaturated ketones having an aryl/alkyl group at the β-carbon took longer times and higher temperature. The difference in the reactivity between six and five membered enones and various thiols was utilized to demonstrate selective thia-Michael addition reaction during intermolecular competition studies.

42 citations


Journal ArticleDOI
TL;DR: In this paper, high-intensity low-calorie sweeteners saccharin, acesulfame-K, sucralose and aspartame were used as a replacement for sucrose in the manufacture of burfi.
Abstract: High-intensity low-calorie sweeteners saccharin, acesulfame-K, sucralose and aspartame were used as a replacement for sucrose in the manufacture of burfi. Burfi sweetened with low-calorie sweeteners ranked lower (P < 0.05) but was still acceptable in various textural attributes at all periods of storage in comparison to the control with sucrose. The low hardness, adhesiveness, springiness and accordingly, gumminess and chewiness in burfi samples sweetened with low-calorie sweeteners were because of the lack of compactness. It was evident from the scanning electron microscopy that the compactness of the network in burfi decreased with the use of low-calorie sweeteners. The results of the sensory evaluation have shown the successful use of low-calorie sweeteners in the preparation of burfi with a slight difference in its overall acceptability, thus providing an alternate variety to the health-conscious consumers. PRACTICAL APPLICATIONS The consumption of sweets is an integral part of the Indian dietary system. An estimated 54% of India's milk production is converted into products, both traditional and western, with 50% share of traditional products. But in recent years, the manufacturers are diversifying the production to include the specialty items that cater to specific targeted populations. Diabetic-friendly traditional sweet is a new category for such products, the production of which is being contemplated by many enterprising manufacturers. The results have shown the possibility of using low-calorie sweeteners in the preparation of indigenous dairy products, i.e., burfi. The manufacture of indigenous dairy products with low-calorie sweeteners will provide a successful outlet for traditional milk products, and this will provide an alternate variety to the health-conscious consumers.

22 citations


Proceedings ArticleDOI
12 Nov 2007
TL;DR: This work compares two camera selection methods, the first maximizes PSNR for the user's view without considering the cameras' available energy whereas the second uses knowledge of available energy at the cameras to maximize network lifetime.
Abstract: We examine the trade-off between lifetime and distortion in image sensor networks deployed for gathering visual information over a monitored region. Users navigate over the monitored region by specifying a viewpoint that varies with time, and the network attempts to meet the user requirement by synthesizing the desired view using a selection of cameras. We compare two camera selection methods, the first maximizes PSNR for the user's view without considering the cameras' available energy whereas the second uses knowledge of available energy at the cameras to maximize network lifetime. Our simulation results demonstrate a clear trade-off between the two strategies, with selection based on energy alone performing up to 3 dB worse initially than the PSNR based selection yet providing significantly higher coverage lifetime. In addition, we observe that under a fixed total energy constraint, more cameras with lower energy per node are preferable over fewer cameras with higher energy per node. Our results suggest that a hybrid or adaptive camera selection algorithm may provide the optimal lifetime-distortion trade-off.

15 citations


Journal ArticleDOI
TL;DR: No significant difference in the allele or genotype distribution of CCR2 V64I polymorphism was observed, indicating that there is no association between CCR1 V64i polymorphism and susceptibility to HIV infection in North Indian population.
Abstract: Substitution of V64I in CCR2 relates to delayed progression to AIDS and protects against HIV-1 infection. We examined the distribution of V64I in HIV-infected and healthy North Indian subjects. No significant difference in the allele or genotype distribution of CCR2 V64I polymorphism was observed, indicating that there is no association between CCR2 V64I polymorphism and susceptibility to HIV infection in North Indian population.

14 citations


Proceedings Article
01 Jan 2007
TL;DR: It is demonstrated that, through suitable pre-processing of data, significant improvements in compression performance can be obtained as compared to a direct application of lossless data compression methods.
Abstract: Color lookup tables (CLUTs) that are embedded in printer firmware consume precious flash memory. In order to conserve memory and thereby reduce cost, it is desirable to compress CLUTs prior to storage and restore tables as required. In this paper, we investigate methods for lossless compression of CLUTs. We demonstrate that, through suitable pre-processing of data, significant improvements in compression performance can be obtained as compared to a direct application of lossless data compression methods. In particular, the gains in performance with the proposed methods are accomplished by exploiting the characteristics of CLUT data and utilizing a combination of hierarchical differential encoding and re-ordering for the preprocessing. Experimental results over a representative data set indicate that the proposed methods can result in a 26% reduction in memory requirements in comparison to direct compression. As compared to uncompressed tables this corresponds to a memory saving of 68%.

Journal Article
TL;DR: A gradual, steady and significant increase in corms produced per plant, corm size and weight as well as number of cormels per plant was observed with increasing fertilizer levels recording highest values at N50P25K25 g/m2.
Abstract: Investigations were carried out to study the effect of fertilizer levels on vegetative growth, flowering and corm production attributes in gladiolus cv. White Friendship under mango orchard. Significantly maximum number of leaves per plant and number of florets per spike remaining open at a time, were recorded with treatment N50 P25K25 g/m2, whereas significantly maximum plant height was obtained by application of N40 P20 K20 g/m2. Treatment N10P5K5 g/m2 advanced the time for showing colour in the first floret. Application of N40P20K20 g/m2 significantly increased spike length, number of florets per spike, diameter of first floret, life of spike as well as durability of whole spike under field and thus found as optimal dose for these floral characters. A gradual, steady and significant increase in corms produced per plant, corm size and weight as well as number of cormels per plant was observed with increasing fertilizer levels recording highest values at N50P25K25 g/m2.

Journal ArticleDOI
TL;DR: The results indicated that the nanowire structure results in the up-regulation of production in macrophages of inflammatory cytokines such as IL-1α, and IFN-γ and the down- regulation of IL-6, compared to control wafers.
Abstract: A common problem with medical implants is the biofouling response which can detrimentally damage implants or prevent the implant from function properly. This response is characterized by a thick, frequently avascular, layer of proteins and cells over the implant. To study this problem, we have examined here the adhesion of macrophages and the subsequent expression of inflammatory cytokines on nanowire arrays. We found that the cells on the nanowires typically occupied less area and were more circular than on a flat surface of the same material as the nanowires or tissue culture polystyrene (TCPS) in both the presence and absence of fetal bovine serum. Furthermore, this difference was amplified by pre-coating the surfaces with collagen. The smaller area and circular shape indicated that the cells were not thriving on the surface. Since there was potentially a high amount of cell death on the material, and biofouling is frequently characterized as a chronic inflammation, an eighteen cytokine Luminex † panel was performed on the supernatant from macrophages on nanowires, control wafers, and TCPS. As a positive control for inflammation, lipopolysaccharide (LPS) was added to macrophages on TCPS to estimate the maximum inflammation response of the macrophages. Our results indicated that the nanowire structure results in the up-regulation of production in macrophages of inflammatory cytokines such as IL-1a, and IFN-g and the down-regulation of IL-6, compared to control wafers. In addition, the nanostructure also increased the production of IL-10 which is known as an inhibitor of inflammation. Our results showed that the nanoarchitecture can disrupt cell adhesion and may lead to an inflammatory response.

Proceedings ArticleDOI
15 Apr 2007
TL;DR: It is demonstrated that an iterative probabilistic algorithm for estimation of RNA secondary structure using sequence data from two homologous sequences results in a significant decrease in computation time while simultaneously providing a marginal increase in structural prediction accuracy.
Abstract: We propose an iterative probabilistic algorithm for estimation of RNA secondary structure using sequence data from two homologous sequences. The method is intended to exploit intersequence correlations "encoded" in the form of probabilistic models for alignment and for common secondary structure. In analogy with turbo-decoding in digital communications, we formulate a maximum a posteriori probability objective function for joint structural prediction and sequence alignment using iterations over individual structural and sequential alignment models with soft-input soft-output estimators. As a preliminary step toward realizing this methodology, we present results obtained from incorporating (hard) constraints based on posterior sequence alignment probabilities in joint secondary structure prediction. Through experimental evaluations over available databases of known secondary structure, we demonstrate that this results in a significant decrease in computation time while simultaneously providing a marginal increase in structural prediction accuracy.

Patent
Vishal Monga1, Gaurav Sharma1
05 Oct 2007
TL;DR: In this paper, a method and system for identifying print jobs that are repeats of a previously completed job utilizing an object level hash table was proposed, where received print jobs can be parsed into meaningful classes of objects and a table of hash values can be computed for objects in each class and for each print job.
Abstract: A method and system for identifying print jobs that are repeats of a previously completed job utilizing an object level hash table. Received print jobs can be parsed into meaningful classes of objects and a table of hash values can be computed for objects in each class and for each print job. A synopsis comprising the table of hash values can be retained in a database along with the job specific settings. A newly encountered job can be then declared as a repeat of a previous job based on the hashes for the new job that match the hash values for the previous job stored in the database. The classes of objects are readily determinable in common document formats used for print job submission, such as PDF.

Journal ArticleDOI
TL;DR: Results show that the proposed 4D scanner character- ization technique can significantly outperform standard 3D ap- proaches in the target applications.
Abstract: We propose a novel scanner characterization approach for applications requiring color measurement of hardcopy output in calibration, characterization, and diagnostics applications. The method is advantageous for common practical color printing sys- tems that use more than the minimum of three colorants necessary for subtractive color reproduction; printing with cyan (C), magenta (M), yellow (Y), and black (K) is the most prevalent example we use in our description. The proposed method exploits the fact that for the scenarios in consideration, in addition to the scanner RGB values for a scanned patch, the CMYK control values used to print the patch are also available and can be exploited in characterization. An indexed family of 3D scanner characterizations is created, each characterization providing a mapping from scanner RGB to CIELAB for a fixed value of K, the latter constituting the index for the char- acterization. Combined together, the family of 3D characterizations provides a single 4D characterization that maps scanner RGB ob- tained from scanning a patch and the K control value used for print- ing the patch to a colorimetric CIELAB measurement for the patch. A significant improvement in the robustness of the method to varia- tions in printing is obtained by modifying the K index to utilize the scanned output for a black-only patch printed with the correspond- ing K value instead of directly utilizing the control K value used at the printer. Results show that the proposed 4D scanner character- ization technique can significantly outperform standard 3D ap- proaches in the target applications. © 2007 SPIE and IS&T.

Journal Article
TL;DR: It is suggested that all the doctors concerned with medicolegal work, especially autopsies, should be well versed with postmortem artifacts, because they had to wrong interpretation in number of cases and hence may mislead the course of justice.
Abstract: Postmortem artifacts are commonly encountered problems in routine. They had to wrong interpretation in number of cases especially at the hands of an inexperienced autopsy surgeon and hence may mislead the course of justice. So it is suggested that all the doctors concerned with medicolegal work, especially autopsies, should be well versed with these artifacts. Then only our opinion will be conclusive and aid in the administration of justice.

Proceedings ArticleDOI
12 Nov 2007
TL;DR: This analysis provides a complete characterization of the conditions under which the average color is invariant to displacement misregistration, and reveals that invariance can also be obtained when these conditions are violated for suitable dot shapes and displacements.
Abstract: Misregistration between the color separations of a printed image, which is often inevitable, can cause objectionable color shifts in average color. We analyze the impact of inter-separation misregistration on clustered-dot halftones using Fourier analysis in a lattice framework. Our analysis provides a complete characterization of the conditions under which the average color is invariant to displacement misregistration. In addition to known conditions on colorant spectra and periodicity of the halftones, the work reveals that invariance can also be obtained when these conditions are violated for suitable dot shapes and displacements. Examples for these conditions are included, as is the consideration of traditional halftone configurations.

Proceedings ArticleDOI
01 Nov 2007
TL;DR: In this article, principled heuristics are presented for the purpose of computation reduction based on probabilistic methods, which eliminate the computations over extremely improbable alignments and structures, thereby reducing computation with little or no degradation in accuracy.
Abstract: Prediction of common secondary structure across multiple RNA sequences is known to significantly increase accuracy in comparison with single-sequence based prediction methods However, the computational requirements for joint prediction can often be daunting in comparison to single-sequence prediction As a result, heuristic simplifications are often necessary for this joint estimation problem in order to perform computations on current hardware in reasonable times In this paper, principled heuristics are presented for the purpose of computation reduction based on probabilistic methods The methods presented eliminate the computations over extremely improbable alignments and structures, thereby reducing computation with little or no degradation in accuracy Experimental results over databases of RNA families with known secondary structure validate our methods, demonstrating over a two-fold computational speed up in tests over the 5 S rRNA family, without any compromise in accuracy

Proceedings ArticleDOI
01 Nov 2007
TL;DR: This paper develops a sequential framework for side-informed coding in multi-sensor networks, where each sensor observes linear noise-corrupted measurements, using a Karhunen-Loeve transform with 1 -D scalar coset codes.
Abstract: In this paper, we consider the problem of side-informed coding in applications where the data available at the encoder consists of indirect noisy observations of the signal desired at the decoder. In these scenarios, under Gaussian statistics we show that for a mean-squared distortion metric, the side-informed encoding problem can be decomposed into a "side-informed" minimum mean-squared error (MMSE) estimation followed by side-informed coding of the MMSE estimate, without incurring any rate-distortion penally. By recursively exploiting this decomposition, we develop a sequential framework for side-informed coding in multi-sensor networks, where each sensor observes linear noise-corrupted measurements. We construct a practical realization of this encoder using a Karhunen-Loeve transform with 1 -D scalar coset codes. Simulations demonstrate that simple code constructions based on the estimate-then-code partitioned structure provide improvements over their counterparts that perform the encoding directly without a pre-processing estimation step.

Patent
19 Dec 2007
TL;DR: In this paper, a single halftoning screen is provided for a plurality of separations of a color image, where each tile is offset from a neighboring tile by fixed displacement.
Abstract: PROBLEM TO BE SOLVED: To generate color watermarks having favorable contrast and favorable signal-to-noise ratios for detection at scans of printed images. SOLUTION: A single halftoning screen is provided for a plurality of separations of a color image. The halftoning screen includes periodic tiles, each tile is offset from a neighboring tile by fixed displacement, each of the periodic cells contain first and second regions, a first portion of the first region is substantially identical to a corresponding portion of the second region, and a second portion of the first region is substantially conjugate with a corresponding portion of the second region. The single halftoning screen is used to halftone image data from the color image, and the single halftoning screen is used to halftone the image data. COPYRIGHT: (C)2008,JPO&INPIT

Journal ArticleDOI
TL;DR: In this article, ternary FeCo-Ni nanowires are fabricated within the nanoscale pores of alumina membranes using an electrodeposition frequency of 1,000 Hz, 15 Vrms, consistently and repeatably yield nanowire arrays over membranes several cm2 in extent.

Posted Content
TL;DR: In this paper, a molecular mechanics study using a molecular dynamics software (NAMD) coupled to virtual reality (VR) techniques for intuitive Bio-NanoRobotic prototyping is presented.
Abstract: This paper presents a molecular mechanics study using a molecular dynamics software (NAMD) coupled to virtual reality (VR) techniques for intuitive Bio-NanoRobotic prototyping. Using simulated Bio-Nano environments in VR, the operator can design and characterize through physical simulation and 3-D visualization the behavior of Bio-NanoRobotic components and structures. The main novelty of the proposed simulations is based on the characterization of stiffness performances of passive joints-based deca-alanine protein molecule and active joints-based viral protein motor (VPL) in their native environment. Their use as elementary Bio-NanoRobotic components (1 dof platform) are also simulated and the results discussed.

Journal Article
TL;DR: The subject of Forensic Medicine provides solutions to some of the most urgent concerns in society, and focuses on the areas in which medicine and human behaviour interface with the law and acts as a clinical investigator providing a vital liaison between the investigative process and court of law.
Abstract: The subject of Forensic Medicine provides solutions to some of the most urgent concerns in our society, and focuses on the areas in which medicine and human behaviour interface with the law and acts as a clinical investigator providing a vital liaison between the investigative process and court of law. Till date, no importance has been given for the upliftment of this subject. At many places, the department remains on the most dirtiest and neglected part of the college. In this paper, some problems are highlighted and suggestions have been given for saving the future of this important subject in our country.

Proceedings ArticleDOI
12 Nov 2007
TL;DR: A precise description of each of the requirements of an effective fingerprint should be given and a solution framework to obtain a set of fingerprinted images meeting these requirements is given.
Abstract: Digital fingerprinting techniques aim to embed unique identification information into digital content distributed to individual users in order to track unauthorized use of multimedia files. Fraudulent users may not only attempt to remove the embedded signatures but also may form coalitions in order to remove the embedded fingerprint and disable tracking. This makes the design of fingerprints challenging. An effective fingerprint should not only carry the assigned users information but also guard against the possibility of falsely implicating an innocent user. Furthermore, in possible collusion scenarios, the colluded copies should identify each of the colluders. The embedded fingerprints should be imperceptible to maintain the commercial value of the content and preferably the fingerprint-based identification should survive content preserving signal processing. In this paper we give a precise description of each of these requirements and give a solution framework to obtain a set of fingerprinted images meeting these requirements.

Proceedings ArticleDOI
01 Oct 2007
TL;DR: This work proposes an in-band methodology for end-to-end channel assurance in these scenarios based on speech watermarking that is resilient to low-bit rate coding standards commonly used in these voice communication applications and in mobile telephony and digital voice-over-IP (VoIP).
Abstract: Voice channels are commonly utilized in a wide variety of communication and control scenarios that span the gamut of applications ranging from military and commercial aviation to emergency response applications. Often the existing equipment for these applications utilizes openly accessible voice communication systems that offer no assurance of data security or integrity. It is possible to secure the systems with encryption but this would require significant new investments and introduce interoperability problems with existing equipment. As an alternative, we propose an in-band methodology for end-to-end channel assurance in these scenarios based on speech watermarking. Our speech watermark is resilient to low-bit rate coding standards commonly used in these voice communication applications and in mobile telephony and digital voice-over-IP (VoIP).

Journal ArticleDOI
TL;DR: In this paper, perchloric acid adsorbed on silica gel (HClO4-SiO2) was used as a highly efficient, inexpensive and reusable catalyst for chemoselective carbon-sulfur bond formation by conjugate addition of thiols to α,β-unsaturated ketones under solvent-free conditions and at rt are reported.
Abstract: The scope and limitations of perchloric acid adsorbed on silica gel (HClO4–SiO2) as a highly efficient, inexpensive, and reusable catalyst for chemoselective carbon–sulfur bond formation by conjugate addition of thiols to α,β-unsaturated ketones under solvent-free conditions and at rt are reported. In the case of 1,3-diphenylpropenone, the reactions were best carried out either at 80 °C under solvent-free conditions or at rt in MeOH. The reaction of aryl, arylalkyl, alkyl thiols, and alkane dithiols with cyclic and acyclic α,β-unsaturated ketones afforded excellent yields of the corresponding β-sulfidocarbonyls after 2 min to 2 h. In the case of dithiols, the bis-thia-Michael adducts were formed. The rate of the reaction was found to be dependent on the electronic and steric factors of the α,β-unsaturated ketones and the thiols. A substituent at the β-carbon of the α,β-unsaturated ketone offered steric hindrance for conjugate addition and such substrates required longer times. In case of aromatic thiols, the presence of the nitro group reduced the nucleophilicity of the sulfhydryl sulfur atom resulting in slower rate of reaction for 4-nitrothiophenol compared to that of thiophenol and 4-methylthiophenol. For alkane thiol, the reaction rate was influenced by the steric crowding of the alkyl group attached to the sulfhydryl moiety. The rate of reaction for alkane thiols was sluggish compared to that of aryl thiols. The influence of the β-substituent on the rate of thia-Michael addition was utilized for selective reaction during inter-molecular competitions of cyclohexen-2-one versus 3-methyl-2-cyclohexenone, cyclohexen-2-one versus 4-methyl-3-penten-2-one, and 4-phenyl-3-buten-2-one versus 4-methyl-3-penten-2-one with thiophenol with 100:0, 91:9, and 70:30 selectivities, respectively. The difference in the rate of reaction of thiophenol and 4-nitrothiophenol was also reflected during the inter-molecular competition for the reaction with cyclohexen-2-one with an excellent selectivity of 100:0. The influence of the steric factor of the alkyl group in alkane thiol resulted in 62:38 selectivity during the inter-molecular competition of ethane thiol and tert-butanethiol with cyclohexen-2-one. During inter- and intra-molecular competitions of thia- versus aza- and thia- versus oxa-Michael addition reactions, chemoselective thia-Michael addition took place. The chemoselective thia-Michael addition over aza-Michael addition during intra-molecular competion reactions with 2-aminothiophenol was utilized for an efficient one-pot synthesis of benzothiazepines.