Cyclopropylmethyl Grignard reagents

The cyclopropylmethyl Grignard reagent can only be trapped with electrophiles before rearrangement if the Grignard reagent is generated and treated with the electrophile at -75 °C [54]. 

At the opposite extreme, the cyclopropylmethyl Grignard reagent 35 is present at equilibrium to an extent of greater than 99.9% (49). Two... 

A possible method seemed to be to make use of the Thorpe-Ingold, or gem-dimethyl, effect which, in one statement 49), is that the accumulation of substituents along the chain of a bifunctional system appears to selectively stabilize the corresponding cyclic forms. Maercker and co-workers (6S) have recently used this effect to shift the equilibrium between a 3-butenyl Grignard reagent and a cyclopropyl methyl Grignard reagent in favor of the cyclopropylmethyl compound. 

Since Roberts observed the cyclopropylmethyl I-but-3-enyl Grignard reagent rearrangement in I960, the cyclization of unsaturated Grignard... 

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