Ring enlargement with diazomethane. cycloHeptanone from cyclohexanone

RING ENLARGEMENT WITH DIAZOMETHANE CYCLOHEPTANONE FROM CYCLOHEXANONE 

Reaction of cyclic ketones with diazoraethane leads to ring enlargement. Thus cyctohexanone (I) (1 mol) and diazomethane (1 mol) give /oheptanone (II) in about 60 per cent, yield together with a little epoxide (III) as by product and some cj/cioootanone (IV) resulting from further reaction of cyctoheptanone with diazomethane.  

The cj/cioheptan9ne is readily separated by taking advantage of the experimental fact that it alone forms a soUd bisulphite compound. Diazomethane is conveniently generated in situ from p-tolyl.sulphonylmethylnltrosamlde (Section VII,20). 

A possible mechanism of the reaction is represented by the following scheme  

CAUTION Carry out the preparation in an efficient fume cupboard (hood) since diazomethane is very toxic. 

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VI,34. RING ENLARGEMENT WITH DIAZOMETHANE CYCLOHEPTANONE FROM CYCLOHEXANONE... 

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