Studies On The Application Of Ring-opening Reaction Of Cyclobutenones In Organic Synthesis

As a special kind of small ring compounds, cyclobutenones and derivatives have beenapplied as a key component of natural products and various biologically active molecules, andare also used as one of the important synthetic intermediates which have been widely used in avariety of natural products and important complex molecules due to its high selectivity ofring-opening reaction. Therefore, the synthesis of cyclobutenones and studies of theirring-opening reaction have attracted considerable attention. Although many reactions ofcyclobutenones have been developed in foreign countries, ring-opening conditions and the modeof fracture of multifunctional cyclobutenones are still not be familiar, especially3-aminosubstituted cyclobutene because of a limited synthetic methods. These have restricted theirgeneral use in various fields.Based on3-amino substituted cyclobutenones which have been prepared in our previouswork, we mainly studied the ring-opening reaction and focused on the3-amino substitutedcyclobutenones with various active methylene carbonyl compounds, acetylenic compounds, theirown opening-cyclization reactions. The main results are listed as follows.We have successfully obtained a serious of polysubstitute pyran derivatives by utilizingopening-cyclization reactions of cyclobutenones in the presence of Brnsted acid. The methodexhibits many advantages such as low temperature, high yield, rapid response and so on. Inaddition, a simple and effective method for the synthesis of polysubstitute pyran derivatives hasbeen established.We have developed a new strategy for the regiospecific synthesis of persubstituted phenolsvia a formal [4+2] cycloaddition between cyclobutenones (as1,4-dipoles) and active methyleneketones (cabon-carbon dipolarophiles) in the presence of LDA. Moreover, based on thepersubstituted phenols as substrates, we have prepared acridines derivatives in high yields byusing In(oTf)3as catalyst or by reduction and Friedel-Craft reactions.By using Cu(OTf)2as catalyst, we have presented a new protocol for the synthesis ofsubstituted benzene derivatives via [4+2] cycloaddition between pyrone derivatives which werefrom opening-cyclization reactions of cyclobutenones and acetylenic together with the course ofeliminating carbon dioxide.