Functional π-Gelators and Their Applications

Multicomponent reactions have gained significant importance as a tool for the synthesis of a wide variety of useful compounds, including pharmaceuticals. In this context, the multiple component approach is especially appealing in view of the fact that products are formed in a single step, and the diversity can be readily achieved simply by varying the reacting components. The eco-friendly, solvent-free multicomponent approach opens up numerous possibilities for conducting rapid organic synthesis and functional group transformations more efficiently. Additionally, there are distinct advantages of these solvent-free protocols since they provide reduction or elimination of solvents thereby preventing pollution in organic synthesis “at source”. The chemo-, regio- or stereoselective synthesis of high-value chemical entities and parallel synthesis to generate a library of small molecules will add to the growth of multicomponent solvent-free reactions in the near future. In this review we summarized the results reported mainly within the last 10 years. It is quite clear from the growing number of emerging publications in this field that the possibility to utilize multicomponent technology allows reaction conditions to be accessed that are very valuable for organic synthesis. Therefore, diversity oriented synthesis (DOS) is rapidly becoming one of the paradigms in the process of modern drug discovery. This has spurred research in those fields of chemical investigation that lead to the rapid assembly of not only molecular diversity, but also molecular complexity. As a consequence multi-component as well as domino or related reactions are witnessing a new spring.

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Recent developments in solvent-free multicomponent reactions: a perfect synergy for eco-compatible organic synthesis

Carbon dioxide chemistry (in particular, capture and conversion) has attracted much attention from the scientific community due to global warming associated with positive carbon accumulation. The most widely used chemical absorption technique for carbon capture and storage/sequestration (CCS) would be essentially adopting amino-containing absorbents through formation of C–N bond in terms of mechanistic consideration. However, extensive energy input in desorption and compression process would be a crucial barrier to realize practical CCS. On the other hand, CO2 is very attractive as an environmentally friendly feedstock to replace the hazardous phosgene route for making commodity chemicals, fuels, and materials from a standpoint of green chemistry, whereas the reactions involving CO2 are commonly carried out at high pressure, which may not be economically suitable and also pose safety concerns. The challenge is to develop catalysts that are capable of activating CO2 under low pressure (preferably at 1 atm), and thus incorporating CO2 into organic molecules catalytically. We have proposed a carbon capture and utilization (CCU) strategy as an alternative approach to addressing the energy penalty problem in CCS. The essence of our strategy is to use captured CO2, also considered as the activated form of CO2, which could render this system suitable for accomplishing chemical transformation of CO2 under low pressure to avoid an additional desorption step. Indeed, CO2 could be activated through the formation of carbamate/alkyl carbonate with Lewis basic nitrogen species. In this review, we would like to discuss and update advances on CCU, particularly C–N bond formation with the production of oxazolidinones, quinazolines, carbamates, isocyanates and polyurethanes by using CO2 as C1 feedstock, and CO2 capture by amino-containing absorbents, including conventional aqueous solution of amine, chilled ammonia, amino-functionalized ionic liquids and solid absorbents such as amino-functionalized silica, carbon, polymers and resin, presumably leading to CO2's activation and thus subsequent conversion through C–N bond formation pathway.

Carbon dioxide utilization with C–N bond formation: carbon dioxide capture and subsequent conversion

Advances in the chemical synthesis of C-pyranosides/furanosides are summarized, covering the literature from 2000 to 2016. The majority of the methods take advantage of the construction of the glycosidic C—C bond. These C-glycosylation methods are categorized herein in terms of the glycosyl donor precursors, which are commonly used in O-glycoside synthesis and are easily accessible to nonspecialists. They include glycosyl halides, glycals, sugar acetates, sugar lactols, sugar lactones, 1,2-anhydro sugars, thioglycosides/sulfoxides/sulfones, selenoglycosides/telluroglycosides, methyl glycosides, and glycosyl imidates/phosphates. Mechanistically, C-glycosylation reactions can involve glycosyl electrophilic/cationic species, anionic species, radical species, or transition-metal complexes, which are discussed as subcategories under each type of sugar precursor. Moreover, intramolecular rearrangements, such as the Claisen rearrangement, Ramberg–Backlund rearrangement, and 1,2-Wittig rearrangement, which usuall...

Recent Advances in the Chemical Synthesis of C-Glycosides

Commercially available magnesium perchlorate is reported as an extremely efficient catalyst for the synthesis of α-aminophosphonates. A three-component reaction (3-CR) of an amine, an aldehyde or a ketone, and a di-/trialkyl phosphite (Kabachnik−Fields reaction) took place in one pot under solvent-free conditions to afford the corresponding α-aminophosphonates in high yields and short times. The use of solvent retards the rate of the reaction and requires a much longer reaction time than that for neat conditions. The reactions involving an aldehyde, an aromatic amine without any electron-withdrawing substituent, and a phosphite are carried out at rt. The reactions involving cyclic ketones, aromatic amines with an electron-withdrawing substituent, and aryl alkyl ketone (e.g., acetophenone) require longer reaction times at rt or heating. Magnesium perchlorate was found to be superior to other metal perchlorates and metal triflates during the reaction of 4-methoxybenzaldehyde, 2,4-dinitroaniline, and dimethy...

An extremely efficient three-component reaction of aldehydes/ ketones, amines, and phosphites (Kabachnik-Fields Reaction) for the synthesis of α-aminophosphonates catalyzed by magnesium perchlorate

Facile catalyzed acylation of alcohols, phenols, amines and thiols based on ZrOCl2·8H2O and acetyl chloride in solution and in solvent-free conditions

A new efficient one-pot synthesis of α-amino phosphonates derived from nitro substituted anilines, aldehydes and diethyl phosphite has been carried out by employing 5 mol% of In(OTf) 3 . The method is equally effective for the generation of α-amino phosphonates from various carbonyl compounds and other amines.

In(OTf)3 catalysed simple one-pot synthesis of α-amino phosphonates

A variety of aldehydes reacted in one-pot with ethyl or methyl acetoacetate and urea or thiourea in the presence of 2 mol% In(OTf) 3 furnishing the corresponding dihydropyrimidinones or their thio analogues in very good to excellent yields.

In(OTf)3-catalysed one-pot synthesis of 3,4-dihydropyrimidin-2(lH)-ones

ZrOCl2·8H2O: an efficient Lewis acid catalyst for the one-pot multicomponent synthesis of β-acetamido ketones

A mild, efficient and expeditious method has been developed for the chemoselective conversion of aldehydes to the corresponding acylals in excellent yields, using acetic anhydride in the presence of catalytic amount (0.01–0.1 mol%) of In(OTf) 3 . Ketones remain unaffected under the reaction condition. In(OTf) 3 can be recovered and reused without any loss of its catalytic activity.

Arijit Chakraborty

Papers

Facile catalyzed acylation of alcohols, phenols, amines and thiols based on ZrOCl2·8H2O and acetyl chloride in solution and in solvent-free conditions

In(OTf)3 catalysed simple one-pot synthesis of α-amino phosphonates

In(OTf)3-catalysed one-pot synthesis of 3,4-dihydropyrimidin-2(lH)-ones

ZrOCl2·8H2O: an efficient Lewis acid catalyst for the one-pot multicomponent synthesis of β-acetamido ketones

Indium triflate: a reusable catalyst for expeditious chemoselective conversion of aldehydes to acylals