2566-04-3Relevant academic research and scientific papers
Chemistry of Dihalocyclopropanes XXV. The Influence of Halogen Substituents on the Vinylcyclopropylidene-Cyclopentenylidene Rearrangement
Holm, Kjetil H.,Mohamed, Elhossain Ali,Skatteboel, Lars
, p. 500 - 505 (2007/10/02)
Starting from 2,2-dibromocyclopropanecarbaldehyde and its 1-methyl analogue, some chloro- and bromo-vinyl-substituted derivatives have been prepared, and their reactions with methyllithium studied at 0 and -78 deg C with emphasis on the formation of cyclopentadienes and allenes.Most reactions produced allenes, monobromides and bicyclopropylidenes.A rearrangement product, viz. 1-chloro-4-methylcyclopentadiene, was only encountered from the reaction of (E)-1,1-dibromo-2-(2-chloroethenyl)cyclopropane.The electronic effect of a chlorine substituent does not influence significantly the allene to cyclopentadiene ratio, which seems to be governed mainly by steric interactions.Reactions of 1,1-dibromo-2-(2,2-dibromoethenyl)cyclopropane and its 2-methyl analogue furnished the corresponding ethynyl derivatives as sole products; lithium-bromine exchange occurred preferentially at the vinylic carbon.
