Sudipta Raha Roy

Chemoselective Reduction of the Carbonyl Functionality through Hydrosilylation: Integrating Click Catalysis with Hydrosilylation in One Pot

Herein we report the chemoselective reduction of the carbonyl functionality via hydrosilylation using a copper(I) catalyst bearing the abnormal N-heterocyclic carbene 1 with low (0.25 mol %) catalyst loading at ambient temperature in excellent yield within a very short reaction time. The hydrosilylation reaction of α,β-unsaturated carbonyl compounds takes place selectively toward 1,2-addition (C═O) to yield the corresponding allyl alcohols in good yields. Moreover, when two reducible functional groups such as imine and ketone groups are present in the same molecule, this catalyst selectively reduces the ketone functionality. Further, 1 was used in a consecutive fashion by combining the Huisgen cycloaddition and hydrosilylation reactions in one pot, yielding a range of functionalized triazole substituted alcohols in excellent yields.

The palladium and copper contrast: a twist to products of different chemotypes and altered mechanistic pathways

A novel contrast in palladium and copper catalysis is revealed to form products of different chemotypes resulting in a phenazine to azoarene twist through an altered mechanistic pathway (from non-radical C–H activation mode of C–N coupling to radical N–N coupling) during the oxidative self-coupling of anilines catalysed by Pd–Ag and Cu–Ag nanoclusters.

Preferred Secondary Structures as a Possible Driving Force for Macrocyclization

Abstract The purpose of the work described in this paper was to explore links that may exist between conformational bias in macrocyclic products and the ease with which they are formed in solid phase S N Ar reactions. Solid phase synthesis of compounds 2 proceeds more efficiently than of compounds 3 under similar conditions. Compounds 2 were designed to mimic β-turn conformations in the dipeptide residues whereas compounds 3 were thought to be unable to show a similar conformational preference. The second assertion was shown to be correct but, surprisingly, CD, NMR, and molecular simulation experiments for 2a indicate another conformation is preferred in solution. This may involve H-bonding of the asparagine side-chain to a backbone amide-carbonyl. Molecular dynamics simulations indicate that cyclization to form compound 2a is statistically more favorable than that to form 3a .

Syntheses of second generation, 14-membered ring β-turn mimics

Efficient solid phase syntheses of the constrained β-turn peptidomimetics 1–3 were devised, and the conformational properties of three representative compounds in DMSO were determined.