Pranab K. Shyam

Synthesis of Sulfones and Sulfonamides via Sulfinate Anions: Revisiting the Utility of Thiosulfonates

Simple and high-yielding strategies for the production of a variety of sulfones and sulfonamides, using thiosulfonates synthesized by copper-catalyzed aerobic dimerization, are reported. Although thiosulfonates are an old class of compound, practical methods for their synthesis and utilization have not been rigorously developed. In this study, we revisit the reactions of easily accessible thiosulfonates to form sulfinate anions. Because of the similar reactivity of thiosulfonates and metal sulfinates derived from toxic SO2, thiosulfinates are proposed to be stable, nontoxic alternatives to metal sulfinate salts.

Copper–dienamine catalysis: γ-oxyamination of α,β-unsaturated aldehydes

A multicatalytic system composed of copper complexes and sec-amine compounds is proposed for γ-oxyamination of α,β-unsaturated aldehydes. Using copper complexes in dienamine catalysis expands the scope of the reaction to include TEMPO radicals. Furthermore, copper catalysts oxidize allylic alcohols to form α,β-unsaturated aldehydes, enabling the one-pot oxidation/oxyamination of allylic alcohols.

Enantioselective synthesis and antioxidant activity of 3,4,5-substituted piperidine derivatives

In this study, 3,4,5-trisubstituted piperidines were synthesized enantioselectively, and their antioxidant activity was evaluated. The 3,4,5-trisubstituted piperidines containing TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and a spatially proximal hydroxy group showed good antioxidant activity. Some of these compounds showed IC50 values in a nanomolar range, comparable to that of TEMPO. Probably the TEMPO generated from the homolysis of the CON bond of 3,4,5-trisubstituted piperidines functions as a radical-scavenging entity, and the hydroxy group of piperidines has a synergistic effect to the antioxidant activity.