Abstract

Nucleophilic addition to carbon-nitrogen double bonds (imines) represents one of the most common strategies for the synthesis of amine derivatives. In order to circumvent the problem associated with low reactivity of imines in nucleophilic addition, various imines with electron-withdrawing groups at nitrogen have been studied, and many of them were successfully applied in asymmetric methodologies. Especially N-carbamoyl imines were found to be useful in the enantioselective synthesis of various organic compounds, due to their increased reactivity toward nucleophiles as well as limited difficulties connected with the removal of the carbamoyl moiety in target molecules. The aim of this review is to cover enantioselective methods based on N-carbamoyl imines, focusing on synthetically useful protocols.

Highlights

  • Nucleophilic addition to carbon–nitrogen double bonds represents one of the most common strategies for the synthesis of amine derivatives

  • In order to circumvent the problem associated with low reactivity of imines in nucleophilic addition, various imines with electron-withdrawing groups at nitrogen have been studied, and many of them were successfully applied in asymmetric methodologies

  • N-carbamoyl imines were found to be useful in the enantioselective synthesis of various organic compounds, due to their increased reactivity toward nucleophiles as well as limited difficulties connected with the removal of the carbamoyl moiety in target molecules

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Summary

Introduction

The initial synthesis of these types of compounds was reported by Stavrovskaya et al in 1970 in a reaction of diethylacetals with methyl carbamates that yielded N-carbamoyl-imine 4 (Scheme 1).[6]. In order to bypass this important limitation, Collet and co-workers reported the synthesis of N-Boc imines for the first time in 1993 (Scheme 2).[8] They found that it was beneficial to use more conventional protecting groups, such as Boc, Fmoc, or Cbz, which were already being used in peptide chemistry. The first example of enantioselective reaction using N-Boc imines was reported by Lipton and co-workers in 1996.11 Since several research groups have devoted their efforts to the development of new methodologies based on N-carbamoyl imines. The coverage of the present review extends generally until December 2012, selected more recent references have been included

Organometallic approaches
Mannich reaction
Aza-Henry reaction
Other reactions
Organocatalytic approaches
Organocatalytic Strecker reactions
Organocatalytic Mannich reactions
Findings
Conclusions

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