The reaction of 2-chlorobicyclo[2.2.1]heptene with methyllithium

✍ Scribed by Paul G. Gassman; Thomas J. Atkins

• Publisher: Elsevier Science
• Year: 1975
• Tongue: French
• Weight: 172 KB
• Volume: 16
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)75065-9

✦ Synopsis

The reaction of methyllithium with 2-chlorobicyclo[2.2.1]heptene (j,) has been reported to produce P-methylbicyclo[2.2.l]heptene (x) in 73% yield.2 This appeared to be a unique example of a substitution of a vinylic chloride by an alkyl group through reaction with an organolithium reagent. Whereas, alkyllithium reagents were not noted for such substitution reactions, the replacement of vinylic halides through reaction with aryllithium had ample precedent.3'" This substitution of halide by aryl was established to proceed via dehydrohalogenation of the vinylic halide to an alkyne and subsequent addition of the aryllithium to the acetylenic linkage.3 In view of this background, we deemed it of interest to determine whether bicyclo[2.2.1]heptyne (2) was an intermediate in the conversion of 1 into &. We now wish to report the results of this mechanistic study. If the reaction of 2-chlorobicyclo[2.2.l]heptene (I) with methyllithium proceeded via 2, the first part of the process would involve removal of the vinylic proton followed by loss of chloride. Addition of methyllithiumto