Hydroxyapatite as a bifunctional nanocatalyst for solventless Henry reaction: A demonstration of morphology dependent catalysis

In the current investigation, HA nanorods and nanoplates with a high surface area have been synthesized using the chemical precipitation method via alcogel formation employing L-arginine as a crystal growth...

Asymmetric Synthesis of Tetrasubstituted Cyclic Amines via Aza-Henry Reaction using Cinchona Alkaloid Sulfonamide/Zinc(II) Catalysts

The first enantioselective aza-Henry reaction of non-activated cyclic iminoesters, derived from cyclic amino acids, has been developed. Good yields and enantioselectivities were observed for the reaction using our original cinchona...

Zwitterionic imidazolium salt: an effective green organocatalyst in synthetic chemistry

An environmentally benign, stable yet efficient organocatalyst is highly desirable from the viewpoint of green chemistry and catalysis. Imidazole-based zwitterionic-type molten salts are a new type of organocatalysts with high catalytic application in various organic transformations with added advantage of room temperature ionic liquid (RTIL) property. Most importantly, these ionic-liquid catalysts are easily recyclable and subsequently reusable for multiple times without loss of significant catalytic efficiency. It has also been evident that C2–H of the imidazole has a vital role in catalyzing the reaction via electrophilic activation. Moreover, by changing the cations and/or anions, the properties of ILs can be tuned in many ways. In this article, the role of imidazolium zwitterionic molten salts as an organocatalyst for selective organic transformations including syn-selective aza-Henry reaction, Erlenmeyer reaction, synthesis of different heterocycles and their functionalization and regioselective ring-opening reactions has been elaborated chronically which will definitely be helping to the readers to explore this new class of organocatalyst for further applications.

Asymmetric Henry Reaction of Nitromethane with Substituted Aldehydes Catalyzed by Novel In Situ Generated Chiral Bis(β-Amino Alcohol-Cu(OAc)2·H2O Complex

Novel chiral thiophene-2,5-bis(β-amino alcohol) ligands (L1–L5) were designed and synthesized from thiophene-2,5-dicarbaldehyde (3) with chiral β-amino alcohols (4a–e) in 4 steps with overall 23% yields. An in situ generated L-Cu(OAc)2·H2O catalyst system was found to be highly capable catalyst for the asymmetric Henry reaction of nitromethane (7) with various substituted aromatic aldehydes (6a–m) producing chiral nitroaldols product (8a–m) with excellent enantiomeric purity (up to 94.6% ee) and up to >99% chemical yields. 20 mol% of L4-Cu(OAc)2 catalyst complex in EtOH was effective for the asymmetric Henry transformation in 24 h, at ambient temperature. Ease of ligand synthesis, use of green solvent, base free reaction, mild reaction conditions, high yields and excellent enantioselectivity are all key factors that make this catalytic system robust and highly desirable for the access of versatile building block β-nitro alcohol in practical catalytic usage via asymmetric Henry reaction.

Group 11 Pincer Oxazoline Complexes

The synthesis and characterization of new copper pincer complexes via cyclometallation of potentially anionic pincer ligands with C1 point group symmetry is reported. All of these complexes have been characterized by single crystal X-ray diffraction method, which confirms the proposed tridentate binding mode of pincer ligand and the formation of an amido N-Cu bond. The reactivity of two of the complexes was investigated towards C-C bond formation reaction, notably the Henry reaction. One of the complexes, which was derived from the achiral pincer ligand, is shown to be a suitable catalyst for the Henry reaction under the standard conditions. The Henry or nitroaldol reaction is one of the organic reactions which affords a C-C bond. The product of this reaction is a β-nitro alcohol which is formed by addition of a nitroalkane to a carbonyl compound.