One-Step Conversion of Oxetane-Fused to 1,3-Oxazine-Fused Steroids

摘要: In a ring-expansion reaction, alkyl and aryl nitriles, in the presence of tetrafluoroboric acid-diethyl ether complex, react with 3-methoxy-16β,17β-dihydro-4'H-oxeto[3',2':16,17]estra-1,3,5(10)-triene to give 3-methoxy-16β,17β-dihydro-4'H-[1,3]-oxazino[5',6':16,17]estra-1,3,5(10)-triene derivatives. Under similar conditions 3-methoxy-16α,17α-dihydro-4'H-oxeto[3',2':16,17]estra-1,3,5(10)-triene undergoes a Wagner-Meerwein rearrangement.