Palladium-catalyzed [4 + 3]-annulations of oxotryptamines with allyl dicarbonates: an approach toward spiro[azepane-4,3′-oxindoles]

Abstract

A novel palladium-catalyzed [4 + 3]-annulation of oxotryptamines with allyl dicarbonates has been developed. The reaction furnishes various spiro[azepane-4,3′-oxindoles] in moderate to excellent yields (30%–96%) with a Z/E ratio up to >20 : 1 through a tandem allylic substitution strategy. This protocol enables the synthesis of a wide range of seven-membered spirocyclic oxindoles with high Z-selectivity. In addition, the gram-scale reaction and further derivatizations were also investigated, demonstrating the synthetic utility of this approach.