Mechanistic Investigations into the Photochemistry of 4-Allyl-tetrazolones in Solution: A New Approach to the Synthesis of 3,4-Dihydro-pyrimidinones
作者:Luís M. T. Frija、Igor V. Khmelinskii、M. Lurdes S. Cristiano
DOI:10.1021/jo060164j
日期:2006.4.1
Photolysis (λ = 254 nm) of 4-allyl-tetrazolones 2a−c was carried out in methanol, 1-propanol, 1-hexanol, acetonitrile, and cyclohexane. The sole primary photochemical process identified was molecular nitrogen elimination, with formation of pyrimidinones 6a−c. Following the primary photocleavage, secondary reactions were observed in acetonitrile and cyclohexane, leading to phenyl-isocyanate (7), aniline
在甲醇,1-丙醇,1-己醇,乙腈和环己烷中进行4-烯丙基-四唑酮2a - c的光解(λ= 254 nm)。唯一确定的主要光化学过程是分子氮的消除,并形成嘧啶酮6a - c。一次光裂解后,在乙腈和环己烷中观察到二次反应,生成异氰酸苯酯(7),苯胺(9)和1-苯基丙-1-烯基异氰酸酯(10a)。在酒精溶液中,主要产物6a - c,即使在延长的辐射下仍能保持光稳定性,从而有可能以很高的收率分离出作为稳定化合物的3,4-二氢嘧啶酮。嘧啶酮6a - c的观察到的光稳定性醇中的芳烃归因于通过可逆的质子转移引起的激发态猝灭,这归因于由于形成氢键而导致的溶剂笼稳定。醇的粘度与观察到的笼效应直接相关。4-烯丙基-四唑酮的光裂解可能导致笼中的三线态自由基对。溶剂粘度对光解量子产率的影响证实了这一假设。此外,溶解的分子氧会激发嘧啶酮的形成,正如三重态中间体所预期的那样,该中间体只能在T-S转化后形成产物分子,并被氧加速。