Tandem Sequences Involving Michael Additions and Sigmatropic Rearrangements

Claisen and related [3,3]-sigmatropic rearrangements have been well described as useful synthetic organic tools. Frequently, the [3,3]-sigmatropic rearrangements are combined with other reactions in a tandem sequence leading to the formation of several bonds in only one synthetic step. This review presents the most relevant advances in tandem sequences combining a conjugate Michael-type addition and a [3,3]-sigmatropic rearrangement. Relevant examples of the use of different types of nucleophiles initiating the tandem sequences, along with detailed commentary illustrating the use of the title sequences in the preparation of synthetically useful building blocks, are presented. Examples of catalytic methodologies based on these tandem sequences are also provided. Finally, the asymmetric version of an inverse tandem [3,3]-rearrangement/ Michael addition sequence oriented to the synthesis of optically active.-substituted delta-amino acids is detailed. 1 Introduction 2 Michael Addition/[3,3]-Rearrangement Sequences 2.1 C-Nucleophiles 2.2 N-Nucleophiles 2.3 P-Nucleophiles 2.4 O-Nucleophiles 3 [3,3]-Rearrangement/Michael Addition Sequences 4 Conclusion