Photocycloaddition of Cyclohex-2-enones to Tetramethoxyethylene: Formation of 2,2,3,3-Tetramethoxy-1-oxaspiro[3.5]non-5-enes
作者:Giuliano Cruciani、Hans-J�rgen Rathjen、Paul Margaretha
DOI:10.1002/hlca.19900730410
日期:1990.6.20
Cyclohex-2-enones 1a–1c undergo photocycloaddition to tetramethoxyethylene in benzene to afford 1-oxa-spiro[3.5]non-5-enes 3 in very good yields. In MeCN as solvent, higher relative amounts of bicyclo[4.2.0]octan-2-ones 4 are formed. Results from similar experiments with the same enones and 2,3-dimethylbut-2-ene or 1,1-dimethoxyethene indicate that the driving force for oxetane formation is a sufficiently
环己基-2-烯酮1a-1c在苯中的四甲氧基乙烯上进行光环加成反应,从而以非常好的收率得到1-oxa-spiro [3.5] non-5-enes 3。在作为溶剂的MeCN中,形成较高相对量的双环[4.2.0]辛烷-2-酮4。使用相同的烯酮和2,3-二甲基丁-2-烯或1,1-二甲氧基乙烯进行的类似实验的结果表明,氧杂环丁烷形成的驱动力是烯酮的E red和E ox之间的氧化还原电势有足够大的差异烯烃。提出了一种用于环烷-2-烯酮+烯烃光环加成的机理,其中环丁烷加成物来自激基复合物中间体,氧杂环丁烷来自随后形成的接触离子对。