Photochemical Acetalization of Carbonyl Compounds in Protic Media Using an in Situ Generated Photocatalyst
作者:H. J. Peter de Lijser、Natalie Ann Rangel
DOI:10.1021/jo0485886
日期:2004.11.1
Carbonyl compounds are conveniently converted into their corresponding dimethyl acetals in good yields and short reaction times by means of a photochemical reaction in methanol with a catalytic amount of chloranil (2,3,5,6-tetrachloro-1,4-benzoquinone, CA) as the sensitizer. Using aldehydes gives better results than using ketones, which also tend to form enol ethers as side products. These results
羰基化合物可通过在甲醇中与催化量的邻苯二甲腈(2,3,5,6-四氯-1,4-苯醌,CA)进行光化学反应,以高收率和较短的反应时间方便地转化为相应的二甲基乙缩醛。作为敏化剂。使用醛比使用酮产生更好的结果,酮也倾向于形成烯醇醚作为副产物。这些结果类似于简单的酸催化的缩醛化反应,表明光化学产生的酸的参与。根据稳态和激光闪光光解数据,提出该反应涉及通过CA与溶剂反应原位生成光催化剂(2,3,5,6-四氯-1,4-氢醌,TCHQ) 。缩醛化过程是由TCHQ的电离引发的,然后质子损失到溶剂或羰基中,从而开始催化反应。光催化剂通过歧化反应再生。