Palladium-Catalyzed Diastereoselective Allylation/Aza-Cope Rearrangement

Significance

Decarboxylative dearomatization-rearomatization has made possible this report of a tandem Pd-catalyzed allylation/aza-Cope rearrangement which generates 2-allyl-substituted heterocycles with tertiary or quaternary carbon centers. The regioselectivities are unusual given that Pd allylations normally occur with attack at the least-hindered end of the allyl fragment. Furthermore, the reaction occurs with high diastereoselectivities, which is rare with acyclic nucleophiles. A variety of heteroaromatic amines provide the same regioselecitivity and high dr values (except for N-methyl benzimidazole), though usually with only moderate yields. Elimination products were commonly seen but less prevalent at higher temperatures. Prenyl and crotyl esters can also be used in the reaction with the less basic heterocyles (benzoxazole and benzothiazole) with benzothiazole substrates generally giving higher yields and dr values.