Strategy chain lengthening

The alternative strategy is to leave the three-membered ring alone and to use a Friedel-Crafts disconnection. Intermediate (37) would be easy to make if the 1X-CH2 group were not there (38) as it would then be a diazoester addition to styrene, a route we discussed in Chapter 30. We can use our chain lengthening procedure (Chapter 31) to go from (38) to (37). 

This Strategy would seem too laborious for practical purposes. It requires the incorporation of each residue in blocked and activated form and removal of the amine-blocking group after each chain lengthening step. 

Focusing on completion of the synthesis, we examined one-carbon chain lengthening strategies based on masked acyl cyanides and on modified Petersen olefinations. Preliminary experiments were not promising, and we considered the modification of our scheme in order to bypass the need for homologation. 

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