Subrata Kumar Chaudhuri

Solvent-free synthesis of 4,4-bis-functionalized-1,6-dienes and 1,6-diynes on the surface of neutral alumina

Abstract An improved procedure has been developed for the synthesis of structurally varied 4,4-bis-functionalized-1,6-dienes and 1,6-diynes through regioselective alkylation of active methylene compounds with several unsymmetrical allyl bromides and propargyl bromide on the surface of neutral alumina impregnated with sodium ethoxide or potassium tert-butoxide in the absence of any solvent under environmentally benign conditions.

Remarkable reactivity of pyridinium chlorochromate adsorbed on neutral alumina under solvent-free conditions

Abstract Pyridinium chlorochromate adsorbed on neutral alumina (PCC-Al 2 O 3 ) under solvent-free conditions has been found to oxidize primary aliphatic alcohols to alkyl alkanoates whereas primary benzylic and primary allylic alcohols produce the corresponding aldehydes. Secondary aliphatic and aromatic alcohols produce ketones without isomerization and polymerization of double bonds, overoxidation and other side-reactions.

Regioselective Aromatic Electrophilic Bromination with Dioxane Dibromide Under Solvent‐Free Conditions

Abstract Highly regioselective ring bromination of aromatic compounds has been accomplished with high yields and good purity using dioxane dibromide (DD) under solvent‐free conditions. Notable features of this methodology include operational simplicity, rapid reactions, excellent control over the degree of bromination, and tolerance of various functional groups during the reaction.

Systematic investigations on the reduction of 4-aryl-4-oxoesters to 1-aryl-1,4-butanediols with methanolic sodium borohydride

Summary 4-Aryl-4-oxoesters undergo facile reduction of both the keto and the ester groups with methanolic NaBH4 at room temperature to yield the corresponding 1-aryl-1,4-butanediols whereas 4-alkyl-4-oxoesters furnish the corresponding 1,4-butanolides via selective reduction of the keto moiety. Results of a detailed and systematic investigation of the reaction are described.

Dioxane dibromide mediated bromination of substituted coumarins under solvent-free conditions.

Summary An efficient solvent-free protocol for regioselective bromination of substituted coumarins has been developed by using dioxane dibromide as the solid brominating agent. The efficacy of the solvent-free protocol has been established. The effects of the electronic nature and location of the substituents on the outcome of the reaction have been rationalized with a proposed mechanism.

Microwave-assisted ammonium formate-mediated Knoevenagel reaction under solvent-free conditions – a green method for C–C bond formation

Abstract Syntheses of structurally varied densely functionalized olefins have been accomplished (23 examples) through microwave-assisted ammonium formate-mediated Knoevenagel condensation of differently substituted aromatic aldehydes with ethyl cyanoacetate, cyanoacetamide, malononitrile, and malonic acid under solvent-free condition in good yield (76–95%) and high purity. The said reactions occur within very short period of time (0.75–3 min) in eco-friendly conditions involving an operationally simple procedure, eliminating any kind of inorganic support, toxic reagent and organic solvent.

Microwave-assisted ammonium formate-mediated synthesis of Hanstzch dihydropyridines under solvent-free conditions – a green protocol

Abstract Microwave-assisted ammonium formate-mediated eco-friendly synthesis of structurally varied Hantzsch dihydropyridines under solvent-free conditions has been successfully accomplished with good yield, minimization of toxic reagents and organic solvents in the process. The elimination of the inorganic support decreased the disposal problem and the extremely small reaction time minimized energy dissipation.

Cyanuric Chloride–Mediated Synthesis of Allylic Chloride—ipso‐ versus tele‐Substitution

Abstract Synthesis of unsymmetrical allylic chlorides has been accomplished using cyanuric chloride in combination with DMF through ipso‐substitution and tele‐substitution by judicious choice of the substituents at appropriate positions of unsymmetrical allyl alcohols, taking care of their electronic and steric properties.

Dioxane Dibromide–Mediated Solvent‐Free Synthesis of Vicinal Dibromides

Abstract Structurally varied vicinal dibromides have been synthesized in high yield and good purity through highly stereoselective anti‐addition of bromine across the olefinic linkages using dioxane dibromide (DD) under solvent‐free conditions.

Formation of Dioxolane on the Surface of Silica–Sulphuric Acid in Dry Media—Chemoselective Protection of Aryl Aldehydes

Abstract Chemoselective protection of aryl aldehydes can be accomplished through the formation of dioxolane on the surface of silica–sulphuric acid under solvent‐free conditions where aliphatic aldehydes, dialkyl ketones, aryl alkyl ketones, and diaryl ketones remain intact.