Reaction of Alkyl and Aryl Grignard Reagents with Trifluoroacetyldihydropyrans and Other Cyclic β-Alkoxy-α,β-unsaturated Trifluoromethylketones
作者:John M Mellor、Gill Reid、Afaf H El-Sagheer、El-Sayed H El-Tamany
DOI:10.1016/s0040-4020(00)00975-3
日期:2000.12
β-unsaturated trifluoromethylketones by 1,4-addition to give as the major products, for example, cis-2,3-disubstituted tetrahydropyrans. In most examples ring opening leads to stereoselective formation of rearranged hemiketals as minor products. Under other conditions with 2,2,2-trifluoro-1-(2-ethoxy-3,4-dihydro-2H-5-pyranyl)-1-ethanone stereoselective ring opening leads to acyclic aldehydes, as minor products
烷基和芳基格氏试剂通过加成1,4-与环状β-烷氧基-α,β-不饱和三氟甲基酮反应生成主要产物,例如,顺式-2,3-二取代的四氢吡喃。在大多数例子中,开环导致作为次要产物的重排半酮的立体选择性形成。在其他条件下,带有2,2,2-三氟-1-(2-乙氧基-3,4-二氢-2 H -5-吡喃基)-1-乙酮的立体选择开环会生成无环醛,作为次要产物,并通过通过添加更多当量的格利雅试剂,是通往一系列二醇的主要途径。在较高温度下不存在其他格氏试剂的情况下,内部氢化物转移可提供无环酯。