摘要
Regioselective decomposition of 11-substituted- 16α, 17α-methyleneazopregna- 1,4-dien- 3, 20-dione Ⅰ proceeded smoothly through thermal decomposition in the presence of BF3·Et2O or HClO4 with high yields. Ⅰ was converted to 11-substituted-16-methylpregna-1, 4, 16（17）-trien-3, 20-dione Ⅱ by the thermal decomposition, while with HClO4 ad a catalyst, 11-substituted-16α, 17α-methylenepregna-1, 4-dien-3, 20-dione Ⅲ was the main product. However, when BF3·Et2O was used as catalyst, a mixture of Ⅱ and Ⅲ（1 ： 3） was obtained.
Regioselective decomposition of 11-substituted- 16α, 17α-methyleneazopregna- 1,4-dien- 3, 20-dione Ⅰ proceeded smoothly through thermal decomposition in the presence of BF3·Et2O or HClO4 with high yields. Ⅰ was converted to 11-substituted-16-methylpregna-1, 4, 16（17）-trien-3, 20-dione Ⅱ by the thermal decomposition, while with HClO4 ad a catalyst, 11-substituted-16α, 17α-methylenepregna-1, 4-dien-3, 20-dione Ⅲ was the main product. However, when BF3·Et2O was used as catalyst, a mixture of Ⅱ and Ⅲ（1 ： 3） was obtained.
