Rhodium(II) catalyzed synthesis of macrocycles incorporating oxindole via O-H/N-H insertion reactions

A wide variety of 10- to 29-membered oxaza-macrocycles incorporating an oxindole unit were synthesized in good yield via rhodium(II) acetate dimer catalyzed intramolecular O-H/N-H insertion reactions. Interestingly, synthesis of C-2-symmetric macrocycles in moderate yield was also demonstrated via head to tail dimerization involving double intermolecular O-H insertion when the spacer length was decreased. The synthesis of chiral macrocycles was also delineated. This study reveals the effect of spacer length on inter-or intramolecular insertion reactions with the remotely placed hydroxyl/amino group.