Diastereotopic group selectivity and chemoselectivity of alkylidene carbene reactions on 8-oxabicyclo[3.2.1]oct-6-ene ring systems
作者:Kevin R. Munro、Louise Male、Neil Spencer、Richard S. Grainger
DOI:10.1039/c3ob41390j
日期:——
spirocyclic dihydrofurans, 1,2-rearrangement to an alkyne and fragmentation to a ketone are competing major pathways for 2-benzyloxy-substituted 8-oxabicyclo[3.2.1]oct-6-ene systems. Dihydrofuran formation is shown to be a result of substitution on the oxabicyclic ring system through comparison with other methods of alkylidene carbene formation.
α,β-环氧-N-叠氮基亚胺的热分解生成的α-羟基亚烷基卡宾在2,4-二甲基-8-氧杂双环[3.2.1] oct-6-上经历非对位基团选择性1,5 C–H插入反应烯环系统。在桥接的氧杂双环的C-3处保护叔醇作为三甲基甲硅烷基醚可以逆转非对映选择性。1,5 C–H插入与OBn基团相邻的次甲基中,1,5 O–R插入C-3的叔醇(R = H)或甲硅烷基醚(R = TMS)中,形成螺环二氢呋喃,1, 2-炔基的重排和酮基的断裂是2-苄氧基取代的8-氧杂双环[3.2.1] oct-6-烯系统竞争的主要途径。通过与亚烷基卡宾形成的其他方法比较,表明二氢呋喃的形成是在氧双环系统上进行取代的结果。