Pd0-catalyzed coupling cyclization reaction of Aryl or 1-alkenyl halides with 1,2-allenyl ketones: scope and mechanism. An efficient assembly of 2,3,4-, 2,3,5-tri- and 2,3,4,5-tetrasubstituted furans

Described herein is the Pd(0)-catalyzed coupling cyclization reaction of 1,2-allenyl ketones with organic halides leading efficiently and conveniently to not only 2,3,4- and 2,3,5-trisubstituted furans but also 2,3,4,5-tetrasubstituted furans. Furthermore, this method showed high substituent-loading capability and tolerance of various substituents. The reactions of 1,2-allenyl ketones 1 e, 1 p, 1 q, and deuterated D]1 c were performed for a mechanistic study, which demonstrated that instead of an enolization pathway, the reaction may proceed via the intermediacy of dienolate palladium and intramolecular nucleophilic attack on the pi-allyl palladium intermediate by the carbonyl oxygen.