A study concerning the mechanism of the LDA-mediated ortho and remote metalation of N,N-dialkyl-2-biphenyl carboxamides (e.g., 4a) is reported. On the basis of site-selective lithiation/electrophile quench experiments, including deuteration, the LDA metalation of 4 is proposed to involve initial amide-base complexation (CIPE) and equilibrium formation of 5, whose fast reaction with an in situ electrophile
methyllithium in the presence of ethyl vinyl ether. A cyclopropane derivative was not obtained from the reaction of 9,9-dibromofluorene (III) or 9,9-dichloro-9H-tribenzo[a.c.e]cycloheptene (IV) with alkyllithium in olefin but 9,9′-bifluorenylidene (IX) and 9,9′-dibromo-9,9′-bifluorenyl (XI) were produced from III and 9-methylene-9H-tribenzo[a.c.e]cycloheptene (XXIII) and 9H-tribenzo-[a.c.e]-cyclohepten-9-ol
Does the reaction between fluorenone and grignard reagents involve free fluorenone anion radicals?
作者:Torben Lund、Morten L. Pedersen、Lars A. Frandsen
DOI:10.1016/0040-4039(94)88472-2
日期:1994.12
The ratio between 1,6- and 1,2-addition in the reactions of electrogenerated fluorenone anion radicals with RX in THF were similar to the ratio obtained in the Grignardreaction of fluorenone with RMgX in THF. This indicates that the addition products in the Grignardreaction may be obtained via the coupling of freely diffusing fluorenone anion radicals with R radicals.