Intermolecular [4+3]-Annulation

By: William Sommer, Aldrich ChemFiles 2009, 9.5, 4.

Aldrich ChemFiles 2009, 9.5, 4.

In 2008, Toste and coworkers developed a new method to synthesize azepines using a Au(III) catalyst.1 Following the work done by the group with sulfoxides showing that the allylgold intermediate can be induced to react as a nucleophile, Shapiro and Toste reacted various propargyl esters with various α,β-unsaturated imines (Scheme 8). It was noted that the highest yields were obtained with substrates containing electron-rich groups on the imine nitrogen. However, the reaction proved to be tolerant of variation at other positions. It was also noticed that electron-donating substituents on the N-aryl and β-aryl groups increase the rate of the cycloaddition.

Scheme 8.

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  1. Shapiro, N. D. et al. J. Am. Chem. Soc. 2008, 130, 9244.

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