3,3-dimethyl-7-methylenecycloocta-1,5-dione, a versatile building block for the preparation of substituted cyclooctadienones and δ-valerolactones
作者:Jerzy A. Bajgrowicz、Martin Petrzilka
DOI:10.1016/s0040-4020(01)90474-0
日期:——
the substituent R and the applied reaction conditions, an acid-catalyzed rearrangement of these hemiketals leads to the cyclooctadienones 12 in either pure form or in admixture with δ-valerolactones 11 or substituted cyclohexenones.
丁二酮与丙二烯的De Mayo反应导致3,3-二甲基-7-亚甲基环辛-1,5-二酮6与相应的头尾加合物5的形成,后者自发地二聚为杂Diels-Alder加合物7。与硼氢化钠或格氏试剂一起还原6,可得到跨环半缩醛9,该半缩醛9可以很容易地异构化(DBU)为它们的共轭类似物10。取决于所选择的底物(9或10,取代基R和所应用的反应条件),这些半缩酮的酸催化重排导致形成环辛二烯酮12可以是纯净形式,也可以与δ-戊内酯11或取代的环己烯酮混合使用。