This article surveys variants of the Claisen rearrangement that are of general use in stereoselective organic synthesis. Recent results concerning the influence of steric and electronic parameters on transition state geometries are highlighted. The impact of the Claisen methodology in modern synthetic strategy and its application for the preparation of highly functionalized derivatives is exemplified.

7.2 – Claisen Rearrangements

Mechanistically intriguing participation of siloxyalkynes occurs in the intramolecular Ru-catalyzed metathesis with terminal alkenes (see scheme; Ms=methanesulfonyl). Combined with efficient protodesilylation, this process resulted in the development of a new method for the synthesis of highly functionalized enones starting from readily accessible acyclic precursors. Heterocyclic and polycyclic compounds were prepared efficiently, which illustrates the generality of this novel method.

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Siloxyalkyne–Alkene Metathesis: Rapid Access to Highly Functionalized Enones

Strain and reactivity: Partners for selective synthesis

FeCl3-Catalyzed aminohalogenation of arylmethylenecyclopropanes and arylvinylidenecyclopropanes and corresponding mechanistic studies.

A carbene cascade reaction that constructs functionalized bridged bicyclic systems from alkynyl diazoesters is presented. The cascade proceeds through diazo decomposition, carbene/alkyne metathesis, and C–H bond insertion. The diazoesters are easily synthesized from cyclic ketones. Substrate ring size and substitution patterns control the connectivity and diastereomeric preference found in the products.

Keith A. Horn

Papers

Silicon in organic synthesis—17 : Cyclopentannulation by thermolysis of (1-trimethylsilylcyclopropyl)ethylenes—the 1-trimethylsilylcyclopropyl anion

Silicon in organic synthesis. 14. Five ring annulation processes based upon thermal rearrangement of (1-trimethylsilylcyclopropyl)ethylenes☆

Silicon in organic syntheis. 13. The 1-trimethylsilylcyclopropyl anion and its formal equivalent

Cycloaddition behavior of heptalene toward triazolinediones