Convenient synthesis of tricyclic N(1)–C(2)-fused oxazino-indolones via [Au(i)] catalyzed hydrocarboxylation of allenes

Abstract

A new [Au(I)] catalyzed intramolecular hydrocarboxylation of allenes is presented as a valuable synthetic route to oxazino-indolones. The use of 3,5-(CF₃)₂–C₆H₃–ImPyAuSbF₆ as the optimal catalyst (5 mol%) was necessary to guarantee (i) wide tolerance of functional groups, (ii) mild reaction conditions (r.t., 16 h), and (iii) high yields (up to 90%). Preliminary attempts towards an enantioselective version (81 : 19 er) are also documented by means of a new family of chiral C₁-symmetric ImPyAuCl complexes.