4-Acetoxyazetidine-2-one과 (3R,4R)-4-acetoxy-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]azetidin-2-one에 2-(tert-butyldimethylsilyloxy)-1,3-butadiene 또는 3-(tert-butyldimethylsilyloxy)-1,3-pentadiene을 염화아연의 존재하에 반응시켰을 때 Diels-Alder 첨가생성물인 cephem 유도체가 얻어졌다. 이 반응에서 diene으로 tert-butyldiemethylsilyl acrylate를 사용하였을 때에는 azetidin-2-one의 4-위치의 acetoxy기가 acryloyloxy로 치환된 화합물이 얻어졌다. 4-phenylsulfonylazetidin-2-one을 dienophile로 사용하여 2-(tert-butyldimethylsilyloxy)-1,3-butadiene과 반응시켰을 때에는 carbacephem은 생성되지 않았고 4-phenylsulfoyl-2-butanone이 얻어졌다. Thiochalcone dimer를 염화아연의 존재하에 4-acetoxyazetidin-2-one과 반응시켰을 때 azetidin-2-one의 고리가 깨어진 화합물이 생성되었고, N-methylacrylamide를 trimethylsilyl trifluoromethanesulfonate와 triethylamine의 존재하에 반응시켜 얻은 2-trimethylsilyloxy-1-aza-1,3-butadiene은 4-acetoxyazetidin-2-one과 Diels-Alder 유형의 반응을 하지 않았다.
Diels-Alder adducts, carbacephems were obtained when 4-acetoxyazetidine-2-one or (3R,4R)-4-acetoxy-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]azetidin-2-one was reacted with 2-(tert-butyldimethylsilyloxy)-1,3-butadiene or with 3-(tert-butyldimethylsilyloxy)-1,3-pentadiene. When tert-butyldiemethylsilyl acrylate was used as the diene, products in which was acetoxy group of 4-acetoxyazetidin-2-one derivatives was substituted by an acryloyloxy group were isolated. When the same reaction was carried out with 4-phenylsulfonylazetidin-2-one as a dienophile with 2-(tert-butyldimethylsilyloxy)-1,3-butadiene, 4-phenylsulfoyl-2-butanone was obtained instead of the expected carbacephem. When dimeric form of thiochalcone was reacted with 4-acetoxyazetidin-2-one in the presence of zinc chloride, the $eta-lactam$ ring of the azetidin-2-one was destructed and no product was isolated. Also, the reaction of 2-trimethylsilyloxy-1-aza-1,3-butadiene, which was obtained from N-methylacrylamide by treatment of trimethylsilyl trifluoromethanesulfonate in the presence of triethylamine, with 4-acetoxyazetidin-2-one did not give any products.
