Promotion of asymmetric aza-claisen rearrangement of N-allylic carboxamides using excess base

Article abstract of DOI:10.1055/s-0031-1289899

The aza-Claisen rearrangement of the enolate of N-(Z)-crotyl-N-(S)- phenethylpropanamide did not proceed in the presence of 1.5 equivalents of LHMDS as a base. However, the use of a large excess of base (10 equiv) promoted the reaction to give N-(S)-phenethyl-anti-2,3-dimethylpent-4-enamide with good stereoselectivities (anti/syn = ca. 95:5). An excess of base stabilized the amide enolates and prevented the decomposition to the ketene to prompt the rearrangement of various carboxamides with good stereoselectivity. This reaction provided a new method for the construction of asymmetric quaternary carbon centers. Georg Thieme Verlag Stuttgart · New York.