Abstract

Primary amine-salicylamides derived from chiral trans-cyclohexane-1,2-diamines are used as organocatalysts for the enantioselective conjugate addition of α,α-disubstituted aldehydes to arylated and heteroarylated nitroalkenes. The reaction is performed in the presence of 4-dimethylaminopyridine as an additive in dichloromethane as a solvent at room temperature. The corresponding enantioenriched γ-nitroaldehydes are obtained with enantioselectivities up to 95%. Theoretical calculations are used to justify the reasons of the stereoinduction.

Highlights

  • The asymmetric synthesis of γ-nitroaldehydes has gained great importance during recent years

  • This is largely due to the utility of the nitro group as a masked functionality to be transformed to a variety of other useful functional groups [4,5], which was well described by Seebach with the term ‘synthetic chameleon’ [6]

  • The enantioselective 1,4-addition reaction of enolizable aldehydes to nitroalkenes promoted by a chiral organocatalyst is one of the most common and convenient procedures for achieving the synthesis of γ-nitroaldehydes in an enantiomerically enriched form [7,8,9,10,11,12]

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Summary

Introduction

The asymmetric synthesis of γ-nitroaldehydes has gained great importance during recent years. They are precursors of γ-aminobutyric acid analogues (GABAs), which exhibit a range of pharmacological activities including antidepressant, anticonvulsant, anxiolytic and others [1,2]. Primary-amine squaramides have been used, as is the case of isosteviol-derived compound 7 [22], and the primary-amine-containing benzimidazole 8 [23] and guanidine 9 [24]. In all these primary-amine organocatalysts, the enantioselectivity is induced by addition

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