Base-promoted(4+3) Annulation Of Acetoxypyrone With Para-Quinone Methides

In the past few decades,various reactions mediated by oxidopyrylium salts play an important role in organic syntheses,and the relevant researches have received a great deal of attentions of many synthetic chemists.Based on the 3-oxidopyrylium chemistry,we have designed and developed a(4+3)annulation of para-quinone methides and 3-oxidopyrylium salt,obtaining a series of oxa-bridged heterocyclic compounds.This dissertation is divided into the following two parts.Part ?: The research progress of the chemistry of oxidopyrylium salts.The introductions of the oxidopyrylium-mediated methodologies are primarily given,among which the current progresses in asymmetric catalytic reactions,cycloaddition reactions as well as their applications in the synthesis of natural products are included.Part ?: The study of base-promoted annulation reaction of acetoxypyrone with para-quinone methides.Based on the 3-oxidopyrylium chemistry in situ formed from acetoxypyrone,we have designed and developed a novel(4+3)annulation of3-oxidopyrylium salt with para-quinone methides.This reaction provides an effective synthesis of a series of bridged cyclic compounds having bridgehead acetal moiety.In the optimization of model reaction conditions,several factors including bases,solvents,substrate equivalents,and substrate leaving groups have been investigated.Notably,the use of urea as an additive could effectively deliver the annulation products with higher yields and regioselectivity.The current work not only expands the methodology design related to the chemistry of para-quinone methides,but also to some extent promotes the application of 3-oxidopyrylium chemistry in organic synthesis.