(2E,6E,NE)-1,8-diethoxy-1,8-dioxo-N-(2-oxo-1-tritylindolin-3-ylidene)octa-2,6-dien-4-amine oxide 在
ytterbium(III) triflate 作用下,
以
甲苯 为溶剂,
反应 36.0h,
以65%的产率得到(1R,2R,3R,4S,6S)-ethyl 6-[(E)-3-ethoxy-3-oxoprop-1-en-1-yl]-2'-oxo-1'-trityl-7-oxa-1-azaspiro[bicyclo[2.2.1]heptane-2,3'-indoline]-3-carboxylate