separation and acetal hydrolysis the title compounds 15 and 16 were obtained in high yields as the first representatives of their class. Complexation of the acetals with Cr(CO)6 gave the corresponding tricarbonylchromium complexes in excellent yields. Subsequent deacetalization afforded the diketone complexes 18 and rac-20, which underwent stereoselective nucleophilic diadditions at –78 °C.
用 NaNH2 和
1,1-二甲氧基乙烯 (7) 处理
1,4-二溴-2,5-二甲氧基苯 (6),得到作为 [2+2] 环加成产物的双环和
三环缩醛,例如 8 和 9中间
芳烃。在色谱分离和
缩醛水解后,标题化合物 15 和 16 以高收率获得,它们是同类中的第一个代表。
缩醛与 Cr(CO)6 的络合得到相应的三羰基
铬络合物,产率极好。随后的脱
缩醛得到二酮配合物 18 和 rac-20,它们在 –78 °C 下进行立体选择性亲核加成。