Probing for a Leaving Group Effect on the Generation and Reactivity of Phenyl Cations

详细信息    查看全文

• 作者：Erika Abitelli ; Stefano Protti ; Maurizio Fagnoni ; Angelo Albini
• 刊名：The Journal of Organic Chemistry
• 出版年：2012
• 出版时间：April 6, 2012
• 年：2012
• 卷：77
• 期：7
• 页码：3501-3507
• 全文大小：300K
• 年卷期：v.77,no.7(April 6, 2012)
• ISSN：1520-6904

文摘

Phenyl cations are smoothly generated by the photoheterolytic cleavage of an Ar鈥揕G bond (LG = leaving group). With the aim of evaluating the scope of the method, a series of 4-methoxy-2-(trimethylsilyl)phenyl derivatives (sulfonic, LG = MeSO₃ and CF₃SO₃, phosphate, LG = (EtO)₂(O)PO esters and the corresponding chloride) have been compared as probes for evaluating the leaving group ability. The photocleavage was a general reaction, with the somewhat surprising order (EtO)₂(O)PO Cl > CF₃SO₃ > MeSO₃ (桅 = 0.50 to 0.16 in CF₃CH₂OH and lower values in MeCN鈥揌₂O). The ensuing reactions did not depend on the LGs but only on the structure of the phenyl cation (the silyl group tuned the triplet to singlet intersystem crossing and the electrophilicity) and on the medium (formation of a complex with water slowed the electrophilic reactions).