5- Bromo-1 -methylcyclopentene

Is it possible to prepare 5-bromo-1-methylcyclopentene in good yield by allylic bromination of 1-methylcyclopentene Explain. 

Retrosynthetic analysis of nitrile 164 disconnects the C-CN bond because it is clear that the six carbons of the methylcyclopentene starting material are more or less intact in the remainder of the molecule. This disconnection requires a C-C bond-forming reaction involving cyanide. Because cyanide is associated with a carbon nucleophile, assign Cj to the cyanide and to the cyclopentene carbon. The synthetic equivalent for Cg is an alkyl halide, and 2-bromo-l-methylcyclopentane (168) is the disconnect product. Bromide 168 is obtained directly from the alkene starting material, but it requires the use of a radical process to generate the anti-Markovnikov product (see Chapter 10, Section 10.8.2). 

Correlations of the rates of El reaction of 1-bromo-l-methylcyclopentene in eight aprotic and three protic solvents with those for respective reactions of MesCBr,... 

It is not possible to form 5-bromo-l-methylcyclopentene in good yield by allylic bromination because several other products are formed. 1-Methylcyclopentene has three different types of allylic hydrogens (labeled with ), all of which can be removed during radical bromination. 

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