The [4+1] annulation of in situ generated dimethoxycarbene to 3-trifluoroacetyl-4H-chromenes led to cyclic ortho esters, trifluoromethylsubstituted dihydrofuro[3,4-b]chromenes. In the case of 2-perfluoroacyl-1H-benzo[f]chromenes, representatives of a new heterocyclic system 7a,8-dihydro-11H-benzo[f]furo[3,4-b]chromene, were formed.
原位生成的二甲氧基羰基与 3-三
氟乙酰基-4H-苯并
吡喃的 [4+1] 环化反应产生了环状正交酯、三
氟甲基取代的二氢
呋喃并[3,4-b]苯并
吡喃。在 2-全
氟乙酰基-1H-苯并[f]色烯的情况下,形成了新杂环系统的代表 7a,8-二氢-11H-苯并[f]
呋喃并[3,4-b]色烯。