Copper-catalyzed cyclization of steroidal acylaminoacetylenes: syntheses of novel 11beta-aryl-17,17- spiro[(4'H,5'-methylene)oxazol]-substituted steroids

A variety of novel 11beta-aryl-17,17-spiro[(4'H,5'-methylene)oxazol]-substituted steroids have been synthesized in moderate to good yields via copper-catalyzed cyclization of acylaminoacetylenes. The best result was obtained with a catalytic amount of CuI in 1:1 benzene-Et3N at 90 degrees C for 30 min (Ar = 3,4-difluorophenyl; R = ethyl; 97% yield)

Jin, C., Burgess, J., Kepler, J., & Cook, C. (2007). Copper-catalyzed cyclization of steroidal acylaminoacetylenes: syntheses of novel 11beta-aryl-17,17- spiro[(4'H,5'-methylene)oxazol]-substituted steroids. Organic Letters, 9(10), 1887-1890.