Organocatalytic Stereoselective Synthesis of Acyclic γ-Nitrothioesters with All-Carbon Quaternary Stereogenic Centers

Catalytic synthesis of 3-aminooxindoles via addition to isatin imine: an update

3-Substituted-3-aminooxindoles have attracted the attention of organic chemist to develop different synthetic methodologies for their synthesis using catalysts. This review covers the recent developments.

Recent Advances in Asymmetric Organocatalyzed Conjugate Additions to Nitroalkenes

The asymmetric conjugate addition of carbon and heteroatom nucleophiles to nitroalkenes is a very interesting tool for the construction of highly functionalized synthetic building blocks. Thanks to the rapid development of asymmetric organocatalysis, significant progress has been made during the last years in achieving efficiently this process, concerning chiral organocatalysts, substrates and reaction conditions. This review surveys the advances in asymmetric organocatalytic conjugate addition reactions to α,β-unsaturated nitroalkenes developed between 2013 and early 2017.

Role of Configuration at C6 in Catalytic Activity of l-Proline-Derived Bifunctional Organocatalysts

l-Proline-derived chiral bifunctional (thio)urea organocatalysts epi-PTU and epi-PU were newly synthesized, and their catalytic performances were compared with their C6 epimeric catalysts PTU and PU in various Michael reactions of nitrostyrene in terms of reactivities and stereoselectivities. The experimental results indicate that a proper relative stereochemistry at C2 and C6 in l-proline-derived bifunctional organocatalysts is important for successful catalysis and that catalysts (PTU and PU) with the 2S,6R configuration are much more efficient.

Stereoselective Synthesis of α-Fluoro-γ-nitro Thioesters under Organocatalytic Conditions

Fluorinated monothiomalonates (F-MTMs) were used as building blocks for the stereoselective synthesis of organofluorine compounds. We present conjugate addition reactions between F-MTMs with nitroolefins that proceed under mild organocatalytic conditions and provide access to α-fluoro-γ-nitro thioesters with adjacent tetrasubstituted and tertiary stereogenic centers. Only 1 mol % of a cinchona alkaloid-urea catalyst is necessary to obtain the addition products in excellent yields and stereoselectivities. The methodology allowed for the straightforward synthesis of a fluorinated analogue of the PAR-2 agonist AC-264613.

L-Proline Derived Bifunctional Organocatalysts: Enantioselective Michael Addition of Dithiomalonates to trans-β-Nitroolefins

A series of novel L-proline derived tertiary amine bifunctional organocatalysts 9 are reported, which were applied to the asymmetric Michael addition of dithiomalonates 2 to trans-β-nitroolefins 1. The reaction proceeded in high yields (up to 99%) with high enantioselectivities (up to 97% ee). The synthetic utility of this methodology was demonstrated in the short synthesis of (R)-phenibut in high yield.

Catalytic Asymmetric Construction of Vicinal Tetrasubstituted Stereocenters by the Mannich Reaction of Linear α-Substituted Monothiomalonates with Isatin N-Boc Ketimines

A highly diastereo- and enantioselective method for the construction of vicinal tetrasubstituted stereocenters through the first catalytic asymmetric Mannich reaction of linear α-substituted MTMs with isatin N-Boc ketimines has been developed. This protocol provides atom-economic synthesis of less accessible 3-aminooxindoles bearing vicinal tetrasubstituted stereocenters. Notably, it also constitutes the first example of stereoselective synthesis of β-amino thioesters bearing vicinal tetrasubstituted stereocenters.