3-Exomethylenecepham sulfoxide esters are obtained in improved yields via cyclization of 3-methyl-2-(4-chlorosulfinyl-2-oxo-3-acylamino-1-azetidinyl)-3-butenoic acid esters under anhydrous conditions with stannic chloride in the presence of both an oxo compound, e.g., an ether such as diethyl ether, a ketone such as acetone or methylethyl ketone, and an unsaturated compound, e.g., an alkene such as 1- or 2-hexene, a non-conjugated alkadiene such as 1,4-hexadiene, a cycloalkene such as cyclohexene, an allene, or a non-conjugated cycloalkadiene such as 1,4-cyclohexadiene.
在无
水条件下,3-甲基-2-(4-
氯亚磺酰基-2-氧代-3-乙酰
氨基-1-氮杂
环丁基)-3-
丁烯酸酯与
氯化锡在氧代化合物(如二
乙醚)、酮(如
丙酮或
甲基乙基酮)和不饱和化合物(如烯烃(如 1- 或 2-))的存在下发生环化反应,可获得产率更高的 3-氧亚甲基
樟脑亚砜酯、醚(如二
乙醚)、酮(如
丙酮或
甲基乙基酮)和不饱和化合物(如烯烃(如 1- 或
2-己烯)、非共轭烷二烯(如
1,4-己二烯)、环
烷烃(如环己 烯)、烯烃或非共轭环烷二烯(如
1,4-环己二烯))。