Group IB Organometallic Chemistry, XIV. Intramolecular ring-closure reactions of novel arylcopper compounds RCuI2. Synthesis of 7,8-dihydrodibenzo[f,h] [1,4]diox-ecin and 7,8-dihydrobenzo-6,9-dimethyl[f,h][1,4]diazecin

Abstract

The reaction of 1, 2-bis{N-[2-(bromomagnesio)benzyl]-N-methylamino}ethane (III) with CuCl{2} results in the formation of 1,2-bis[N-(2-cupriobenzyl)N-methylamino] ethane (I, 2,2'-Cu{2}R{N}) and of the product of intramolecular ring-closure 7,8-dihydrodibenzo-6,9-dimethyl[f,h][1,4]diazecin (VII). The formation of 2,2'-R{N} (VII) is explained in terms of a concerted electron-transfer/C@?C coupling reaction within a complex of the monomagnesium species 2,2'-MgR{N} (VIII) with CuCl{2}. Molecular weight determinations and NMR spectroscopic data for I point to a tetranuclear structure (2,2'-Cu{2}R{N}){2} in which (2,2'-Cu{2}R{N}){2} in which the two multicenter-bonded aryl groups in each of the R{N} ligands are arranged in a trans-manner. This structure accounts for the exclusive formation of 2,2'-R{N} (VII) upon thermal decomposition of I. The interaction of 1,2-bis[2-(bromomagnesio)benzyloxy] ethane (X) with CuCl{2} affords the ring-closed product 7,8-dihydrodibenzo[f,h][1,4] dioxecin (IX) in addition to the organodicopper XII. Thermal decomposition of XII yields 2,2'-R{O} (IX) quantitatively.