D'Erasmo Michael P, Meck Christine, Lewis Chad A, Murelli Ryan P
Department of Chemistry, Brooklyn College, The City University of New York , Brooklyn, New York 11210, United States.
PhD Program in Chemistry, The Graduate Center of The City University of New York , New York, New York 10016, United States.
J Org Chem. 2016 May 6;81(9):3744-51. doi: 10.1021/acs.joc.6b00394. Epub 2016 Apr 8.
α-Hydroxy-γ-pyrone-based oxidopyrylium cycloaddition reactions are useful methods for accessing a highly diverse range of oxabicyclo[3.2.1]octane products. Intermolecular variants of the reaction require the formation of a methyl triflate-based pre-ylide salt that upon treatment with base in the presence of alkenes or alkynes leads to α-methoxyenone-containing bicyclic products. Herein, we describe our discovery that the use of ethanol-stabilized chloroform as solvent leads to the generation of α-ethoxyenone-containing bicyclic byproducts. This three-component process was further optimized by gently heating a mixture of a purified version of the oxidopyrylium dimer in the presence of an alcohol prior to addition of a dipolarophile. Using this convenient procedure, several new oxidopyrylium cycloaddition products can be generated in moderate yields. We also highlight the method in a tandem ring-opening/debenzylation method for the generation of α-hydroxytropolones.
基于α-羟基-γ-吡喃酮的氧化吡喃鎓环加成反应是获得多种氧杂双环[3.2.1]辛烷产物的有用方法。该反应的分子间变体需要形成基于甲基三氟甲磺酸酯的前叶立德盐，该盐在烯烃或炔烃存在下用碱处理时会生成含α-甲氧基烯酮的双环产物。在此，我们描述了我们的发现，即使用乙醇稳定的氯仿作为溶剂会导致生成含α-乙氧基烯酮的双环副产物。通过在加入亲偶极体之前，在醇存在下温和加热氧化吡喃鎓二聚体的纯化版本的混合物，进一步优化了这个三组分过程。使用这个简便的方法，可以以中等产率生成几种新的氧化吡喃鎓环加成产物。我们还在用于生成α-羟基环庚三烯酚酮的串联开环/脱苄基方法中突出了该方法。
