PHOTOCHEMICAL CYCLOADDITION OF CYCLOHEXENONE AND CYCLOPENTENONE TO CONJUGATED DIENES
PHOTOCHEMICAL CYCLOADDITION OF CYCLOHEXENONE AND CYCLOPENTENONE TO CONJUGATED DIENES
复制标题
DOI：
10.1021/jo00935a001
复制
发表时间：
1974-01-01
影响因子：
3.6
通讯作者：
CANTRELL, TS
中科院分区：
文献类型：
--
作者：
CANTRELL, TS
结果2-环己烯酮（1）和2-环戊烯酮（2）确实与几个1，3-二烯发生了光化学环加成反应，通常以[2+ 2]方式进行，烯酮1的反应效率非常高。通过使用大量过量的二烯（> 10摩尔过量），可以在制备规模上在高转化率条件下获得大部分加合物混合物的良好产率。例如，在20倍过量的1，3-丁二烯的存在下照射0.05摩尔1，得到72%的总结构3和4的加合物混合物的分离产率。在表I中列出了1和2与几种代表性二烯的辐射加合物的产率;这些反应都进行到基本上完全消耗烯酮。通常观察到伴随的二烯二聚体的形成是由能量从烯酮三重态转移到二烯的结果。5在这些情况下，这是一个相当有效的方法，如1和1，3-环己二烯，有一个快速的早期积累的二烯二聚体和大部分的烯酮是消耗环加成到二烯二聚体。来自除呋喃和环戊二烯之外的所有二烯的加合物混合物在每种情况下显示仅含有
ResultsWe report here our observations that 2-cyclohexenone (1) and 2-cyclopentenone (2) do in fact undergo photochemical cycloaddition to several 1, 3-dienes, usually in the [2+ 2] manner, and in the case of enone 1, with sur-prisingly high efficiency. By use of a large excess of the diene (> 10-mol excess) it is possible to obtain on a pre-parative scale good yields of most of the adduct mixtures under conditions of high conversion. For example, irradiation of 0.05 mol of 1 in the presence of a 20-fold excess of 1, 3-butadiene gave an isolated yield of 72% of the adduct mixture of gross structures 3 and 4. In Table I are listed yields of adducts from irradiation of 1 and 2 with several representative dienes; these reactions were all run to es-sentially complete consumption of enone. There is usually observed concomitant formation of the diene dimers re-sulting from energy transfer from enone triplets to diene. 5 In those cases where this is a fairly efficient process, such as with 1 and 1, 3-cyclohexadiene, there is a rapid early buildup of diene dimer andmost of the enone is consumed by cycloaddition to the diene dimers. five isomers The adduct mixtures from all dienes except furan and cyclopentadiene were shown in each case to contain only