An efficient synthesis of deoxy-lambertellols was reported through a highly chemo- and diastereoselective intermolecular Diels–Alder cycloaddition between trans-1,2-disiloxybenzocyclobutenes and 2-methylprotoanemonine. Such transformation with δ-substituted γ-alkylidenebutenolides, to prepare new analogues of these tricyclic spirolactones, which would be very difficult to prepare by other ways, was
The auto-oxidation of trans-1,2-disiloxybenzocyclobutene 1 was found to be very efficient, giving endo-peroxide 7 in quantitative yield. Each step of the mechanism of spin-forbidden addition of triplet oxygen O2(3Σg) was studied by both EPR/spin trapping and theoretical studies.
Cycloaddition Reactions of Alkoxy Alkynyl Fischer Carbene Complexes with <i>o</i>-Quinodimethanes (oQDMs)
作者:José Barluenga、Manuel A. Fernández-Rodríguez、Enrique Aguilar
DOI:10.1021/ol026600f
日期:2002.10.1
[reaction: see text] The reaction of o-quinodimethanes (oQDMs) with alkoxy alkynyl Fischer carbenecomplexes is highly dependent on the carbenecomplex. Thus, for arylalkynyl carbenecomplexes, the initial [4 + 2]-cycloadduct evolves opening a new entry to the benzo[b]fluorene skeleton, which is present in many natural products. However, for alkenylalkynyl carbenecomplexes, the reaction takes place
A Powerful <i>o</i>-Quinone Dimethide Strategy for Intermolecular Diels−Alder Cycloadditions
作者:John G. Allen、Martin F. Hentemann、Samuel J. Danishefsky
DOI:10.1021/ja993627u
日期:2000.2.1
Conrotatory thermal fragmentation of trans-1,2-disilyloxybenzocyclobutenes generates o-quinonedimethides at remarkably low temperatures. Smooth stereoselective Diels−Alder cycloaddition with a range of dienophiles provides hydronaphthalene derivatives in excellent yield. Direct oxidative desilylation of the adducts affords the corresponding naphthoquinones. Substitution of the benzene nucleus with