4-Methyl-5-phenyl-1H-pyrazol-3(2H)-one.
01 Jan 2011-Acta Crystallographica Section E-structure Reports Online (International Union of Crystallography)-Vol. 67, Iss: 1
TL;DR: The asymmetric unit of the title compound, C10H10N2O, contains two crystallographically independent molecules with similar geometries, which exist in the keto form, indicating that the compound undergoes enol-to-keto tautomerism during the crystallization process.
Abstract: The asymmetric unit of the title compound, C(10)H(10)N(2)O, contains two crystallographically independent mol-ecules with similar geometries, which exist in the keto form. The C=O bond lengths are 1.2878 (12) A in mol-ecule A and 1.2890 (12) A in mol-ecule B, indicating that the compound undergoes enol-to-keto tautomerism during the crystallization process. In mol-ecule A, the pyrazole ring is approximately planar [maximum deviation = 0.007 (1) A] and forms a dihedral angle of 36.67 (6)° with the attached phenyl ring. In mol-ecule B, the dihedral angle formed between the pyrazole ring [maximum deviation = 0.017 (1) A] and the phenyl ring is 41.19 (6)°. In the crystal, inter-molecular N-H⋯O hydrogen bonds link neighbouring mol-ecules into dimers generating R(2) (2)(8) ring motifs. These dimers are linked into ribbons along [101] via inter-molecular N-H⋯O hydrogen bonds, forming R(4) (2)(10) ring motifs.
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TL;DR: This in silico survey shows that changes in the (anti)aromatic character of π-conjugated heterocycles can be used to fine-tune their hydrogen (H-)bond strengths.
Abstract: This in silico survey shows that changes in the (anti)aromatic character of π-conjugated heterocycles can be used to fine-tune their hydrogen (H-)bond strengths. Upon H-bonding dimerization, the π-electrons of these rings can be polarized to reinforce or disrupt their (anti)aromatic π-conjugated circuits (πCCs) and stabilize or destabilize the resulting H-bonded complexes. H-bonding interactions that enhance aromaticity or relieve antiaromaticity are fortified, whereas those that intensify antiaromaticity or disrupt aromaticity are weakened, relative to analogues lacking full π-circuits. Computed dissected nucleus-independent chemical shifts, NICS(1)(zz), reveal a uniform pattern and document changes in the magnetic (anti)aromatic character of the heterocycles considered. Recognition of this (anti)aromaticity-modulated H-bonding (AMHB) phenomenon offers insights into a range of fields from organocatalysis and self-assembly to pharmaceutical chemistry and molecular biology.
25 citations
19 Jul 2013
TL;DR: A simple method to synthesize β-keto esters from ketones and ethyl chloroformate by changing the base and reagent is developed that can be useful for the synthesis of pharmaceutically important pyrazolones also.
Abstract: Background
Pyrazolones are traditionally synthesized by the reaction of β-keto esters with hydrazine and its derivatives. There are methods to synthesize β-keto esters from esters and aldehydes, but these methods have main limitation in varying the substituents. Often, there are a number of methods such as acylation of enolates in which a chelating effect has been employed to lock the enolate anion using lithium and magnesium salts; however, these methods suffer from inconsistent yields in the case of aliphatic acylation. There are methods to synthesize β-keto esters from ketones like caboxylation of ketone enolates using carbon dioxide and carbon monoxide sources in the presence of palladium or transition metal catalysts. Currently, the most general and simple method to synthesize β-keto ester is the reaction of dimethyl or ethyl carbonate with ketone in the presence of strong bases which also requires long reaction time, use of excessive amount of reagent and inconsistent yield. These factors lead us to develop a simple method to synthesize β-keto esters by changing the base and reagent.
18 citations
References
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TL;DR: This paper could serve as a general literature citation when one or more of the open-source SH ELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.
Abstract: An account is given of the development of the SHELX system of computer programs from SHELX-76 to the present day. In addition to identifying useful innovations that have come into general use through their implementation in SHELX, a critical analysis is presented of the less-successful features, missed opportunities and desirable improvements for future releases of the software. An attempt is made to understand how a program originally designed for photographic intensity data, punched cards and computers over 10000 times slower than an average modern personal computer has managed to survive for so long. SHELXL is the most widely used program for small-molecule refinement and SHELXS and SHELXD are often employed for structure solution despite the availability of objectively superior programs. SHELXL also finds a niche for the refinement of macromolecules against high-resolution or twinned data; SHELXPRO acts as an interface for macromolecular applications. SHELXC, SHELXD and SHELXE are proving useful for the experimental phasing of macromolecules, especially because they are fast and robust and so are often employed in pipelines for high-throughput phasing. This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.
81,116 citations
TL;DR: This paper reports on the current status of structure validation in chemical crystallography and describes the current state of research in this area.
Abstract: Automated structure validation was introduced in chemical crystallography about 12 years ago as a tool to assist practitioners with the exponential growth in crystal structure analyses. Validation has since evolved into an easy-to-use checkCIF/PLATON web-based IUCr service. The result of a crystal structure determination has to be supplied as a CIF-formatted computer-readable file. The checking software tests the data in the CIF for completeness, quality and consistency. In addition, the reported structure is checked for incomplete analysis, errors in the analysis and relevant issues to be verified. A validation report is generated in the form of a list of ALERTS on the issues to be corrected, checked or commented on. Structure validation has largely eliminated obvious problems with structure reports published in IUCr journals, such as refinement in a space group of too low symmetry. This paper reports on the current status of structure validation and possible future extensions.
13,163 citations
10 Mar 1970
8,159 citations
"4-Methyl-5-phenyl-1H-pyrazol-3(2H)-..." refers methods in this paper
...The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. Geometry....
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TL;DR: In this article, a review of the most promising systematic approaches to resolving this enigma was initially developed by the late M. C. Etter, who applied graph theory to recognize, and then utilize, patterns of hydrogen bonding for the understanding and design of molecular crystals.
Abstract: Whereas much of organic chemistry has classically dealt with the preparation and study of the properties of individual molecules, an increasingly significant portion of the activity in chemical research involves understanding and utilizing the nature of the interactions between molecules. Two representative areas of this evolution are supramolecular chemistry and molecular recognition. The interactions between molecules are governed by intermolecular forces whose energetic and geometric properties are much less well understood than those of classical chemical bonds between atoms. Among the strongest of these interactions, however, are hydrogen bonds, whose directional properties are better understood on the local level (that is, for a single hydrogen bond) than many other types of non-bonded interactions. Nevertheless, the means by which to characterize, understand, and predict the consequences of many hydrogen bonds among molecules, and the resulting formation of molecular aggregates (on the microscopic scale) or crystals (on the macroscopic scale) has remained largely enigmatic. One of the most promising systematic approaches to resolving this enigma was initially developed by the late M. C. Etter, who applied graph theory to recognize, and then utilize, patterns of hydrogen bonding for the understanding and design of molecular crystals. In working with Etter's original ideas the power and potential utility of this approach on one hand, and on the other, the need to develop and extend the initial Etter formalism was generally recognized. It with that latter purpose that we originally undertook the present review.
7,616 citations
"4-Methyl-5-phenyl-1H-pyrazol-3(2H)-..." refers background in this paper
...These set of dimers are linked into ribbons along the [101], via intermolecular N1A—H1NA···O1B and N1B—H1NB···O1A hydrogen bonds (Table 1), forming R42(10) ring motifs (Bernstein et al., 1995)....
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...2), intermolecular N2A—H2NA···O1A and N2B—H2NB···O1B hydrogen bonds (Table 1) link the neighbouring molecules to form dimers, generating R22(8) ring motifs (Bernstein et al., 1995)....
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TL;DR: The average lengths of bonds involving the elements H, B, C, N, O, F, Si, P, S, Cl, As, Se, Br, Te, and l in organic compounds are reported in this article.
Abstract: The average lengths of bonds involving the elements H, B, C, N, O, F, Si, P, S, Cl, As, Se, Br, Te, and l in organic compounds are reported.
6,649 citations
"4-Methyl-5-phenyl-1H-pyrazol-3(2H)-..." refers background in this paper
...Bond lengths (Allen et al., 1987) and angles are within the normal ranges and are comparable to the related structures (Loh et al., 2010a,b,c)....
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