Santanu Mukherjee

Catalytic Enantioselective Iodoetherification of Oximes

Catalytic Enantioselective Iodoetherification of Oximes Organocatalysis : The first catalytic enantioselective iodoetherification of oximes is developed using commercially available N-iodosuccinimide. In the presence of a dihydrocinchonidine-derived thiourea (10 mol%), b,g-unsaturated oximes undergo facile iodoetherification to produce D-isoxazolines containing a quaternary stereogenic center generally in high yield with good to excellent enantioselectivity. Angewandte Chemie

Lewis base catalysis by thiourea: N-bromosuccinimide-mediated oxidation of alcohols.

In recent times, (thio)urea derivatives have become synonymous with hydrogen bonding owing to their extensive applicability as small molecule organocatalysts. In this paper, another activation mode by thiourea derivatives, namely via Lewis base catalysis, is disclosed for the NBS-mediated oxidation of alcohols. The mild reaction conditions employed here is suitable for chemoselective oxidation of secondary alcohol in the presence of primary alcohol.

Catalytic Asymmetric Direct Vinylogous Michael Addition of Deconjugated Butenolides to Maleimides for the Construction of Quaternary Stereogenic Centers

Competition under control: A practical and efficient direct asymmetric vinylogous Michael reaction of deconjugated butenolides has been developed (see scheme). The products of this reaction, highly functionalized chiral succinimides, are obtained in excellent yield with high diastereoselectivity (up to d.r.=18:1) and outstanding enantioselectivity (up to e.r.=99.5:0.5).

Organocatalytic Enantioselective Formal C(sp(2))-H Alkylation

An organocatalytic enantioselective formal C(sp(2))-H alkylation is reported. This alkylative desymmetrization of prochiral 2,2-disubstituted cyclopentene-1,3-dione is catalyzed by a bifunctional tertiary aminourea derivative, utilizes air-stable and inexpensive nitroalkanes as the alkylating agents, and delivers synthetically versatile five-membered carbocycles containing an all-carbon quaternary stereogenic center remote from the reaction site in excellent enantioselectivity.

Catalytic enantioselective iodoaminocyclization of hydrazones.

The first catalytic enantioselective iodoaminocyclization of β,γ-unsaturated hydrazones has been developed with the help of a trans-1,2-diaminocyclohexane-derived bifunctional thiourea catalyst and allows for the direct access to Δ(2)-pyrazolines containing a quaternary stereogenic center in high yield with good enantioselectivity (up to 95% yield and 95:5 er).

Catalytic asymmetric synthesis of α,β-disubstituted α,γ-diaminophosphonic acid precursors by Michael addition of α-substituted nitrophosphonates to nitroolefins.

Michael additions of α-substituted nitrophosphonates to various nitroolefins are shown to proceed with high diastereo- and enantioselectivity when catalyzed by a quinine-derived thiourea-tertiary amine bifunctional catalyst and generate α,γ-diaminophosphonic acid precursors with contiguous quaternary and tertiary stereocenters.

Remarkable influence of secondary catalyst site on enantioselective desymmetrization of cyclopentenedione

An efficient, robust and highly enantioselective catalytic desymmetrization of 2,2-disubstituted cyclopentene-1,3-diones is developed via direct vinylogous nucleophilic addition of deconjugated butenolides. A remarkable influence of the secondary catalyst site on the enantioselectivity points towards an intriguing mechanistic scenario, possibly by triggering a change in catalyst conformation.

Synergistic Lewis base and anion-binding catalysis for the enantioselective vinylogous addition of deconjugated butenolides to allenoates

An enantioselective vinylogous umpolung addition of deconjugated butenolides to allenoates has been developed for the first time with the help of synergistic combination of an achiral phosphine and a chiral squaramide, and represents the first example of a catalytic enantioselective Cγ-Cγ bond formation between two different carbonyl partners.

Highly enantioselective Diels-Alder reactions of maleimides catalyzed by activated chiral oxazaborolidines.

Diels-Alder reactions of various combinations of maleimides and 1,3-dienes with cationic oxazaborolidines as catalysts have been shown to be highly efficient and enantioselective.

Catalytic Aldol–Cyclization Cascade of 3-Isothiocyanato Oxindoles with α-Ketophosphonates for the Enantioselective Synthesis of β-Amino-α-hydroxyphosphonates

A cascade aldol-cyclization reaction between 3-isothiocyanato oxindoles and α-ketophosphonates has been developed for the synthesis of β-amino-α-hydroxyphosphonate derivatives. Catalyzed by a quinine-based tertiary amino-thiourea derivative, this reaction delivers 2-thioxooxazolidinyl phosphonates based on a spirooxindole scaffold bearing two contiguous quaternary stereogenic centers in high yields with excellent diastereo- (up to >20:1 dr) and enantioselectivities (up to >99:1 er).