Regioselectivity of the Base-Induced Ring Cleavage of 1-Oxygenated Derivatives of Cyclobutabenzene
作者:Abha Gokhale、Peter Schiess
DOI:10.1002/hlca.19980810207
日期:1998.2.4
products through distal and/or proximal cleavage of the strained four-membered ring via benzyl carbanion 4 and/or aryl carbanion 5. A systematic study of this process reveals the relative stability of the two isomeric carbanions 4 and 5 as a key factor in determining the course of the ring-cleavage reaction. While benzyl carbanions 4 can be trapped with carbon electrophiles, attempts at trapping aryl
氧基阴离子3从1,2- dihydrocyclobutabenzen -1-酮生成1通过添加带电荷的亲核试剂的或由1-羟基-1,2- dihydrocyclobutabenzenes 2通过去质子化用碱导致稳定的产品通过远端和/或近端的裂解通过苄基碳负离子4和/或芳基碳负离子5拉紧四元环。对这一过程的系统研究表明,两个同分异构碳负离子4和5的相对稳定性是决定环断裂反应过程的关键因素。而苄基碳负离子4可以被碳亲电试剂捕获,尝试用非H +亲电试剂捕获芳基碳负离子5失败。在质子溶剂中,叔醇2的镁盐与其碱金属盐相比,具有更高的近端裂解速率。由此,我们得出结论,与苄基碳负离子4相比,游离芳基碳负离子5仅是瞬时存在的。近侧C,C-键裂解似乎通过质子化或者发生5从快速,可逆平衡3 ⇌ 5,其中3甚至在质子溶剂中可能占主导地位,甚至可能在芳香族C原子处通过限速质子化3来绕过游离阴离子5。因此,在确定酮1和