Intramolecular Vinylation of Secondary and Tertiary Organolithiums
摘要:
Deprotonation of benzylic ureas, carbamates, and thiocarbamates bearing N'-alkenyl substituents generates carbanions which undergo intramolecular migration of the alkenyl group to the carbanionic center. Solvolysis of the urea products generates alpha-alkenylated amines. With an enantiomerically pure starting urea, migration proceeds stereospecifically, generating in enantiomerically enriched form products containing allylic quaternary stereogenic centers bearing N. Computational and in situ IR studies suggest that the reaction, formally a nucleophilic substitution at an sp(2) carbon atom, proceeds by a concerted addition-elimination pathway.
enriched N-aryl allylic thiocarbamates. Formation of an allyllithium derivative promotes intramolecular N to C aryl migration to the position α to sulfur, generally with good stereospecificity. The substrates may themselves be obtained by Pd-catalyzed enantioselective [3,3]-sigmatropic rearrangement of N-aryl O-allyl thiocarbamates. Solvolysis of the product thiocarbamates yields tertiary thiols, which