Rhodium catalyzed (1â0.1 mol%) decomposition of 2-(3-diazo-2-oxopropyl)-2-methyldioxolane 1a or 2-(3-diazo-1-methyl-2-oxopropyl)-2-methyldioxolane 1b in the presence of a catalytic amount of TMSCl (10 mol%), yielded 4,7-dioxocane 3a (91%) or 3b (49%), whereas similar reaction in the absence of TMSCl caused 1,2-rearrangement to give bicyclobutanones 2a or 2b, respectively; Lewis acid-base catalysis by TMSCl of the ring-expansion of a bicyclooxonium ylide intermediate is revealed.
                                    在催化量的 TMSCl(10 mol%)存在下,
铑催化(1-0.1 mol%)2-(3-重氮-2-氧代丙基)-2-甲基二
氧戊环 1a 或 2-(3-重氮-1-甲基-2-氧代丙基)-2-甲基二
氧戊环 1b 的分解,分别生成 4,7-二氧代
环己烷 3a(91%)或 3b(49%),而在没有 TMSCl 的情况下,类似的反应导致 1,2-重排,分别生成双
环丁酮 2a 或 2b;TMSCl 对双环氧鎓
亚胺中间体的环扩的刘易斯酸碱催化作用得以揭示。