Ring Enlargement by Side Chain Incorporation

This Chapter is subdivided into carbocycle, lactam, and lactone forming reactions according to the structural classes of the products formed by the ring enlargement. 

1) An isomerization prior to the ring expansion has been observed. Thus, aldol product A containing a six-membered ring gave the ring enlarged product B, which can only be derived from the alternative six-membered intermediate, C [5]. 

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VII.2. Ring Enlargement by Side Chain Incorporation with Lactam Formation... 

The smallest ring expanded by this method was seven-membered (VII/13, n = 6) [2] [4] [11]. The number of carbon atoms incorporated by this method ranges between two and four. A side reaction predominates when attempts were made to incorporate a three carbon atom unit from a butanoate chain as in VII/19. Instead of the expected ring enlargement product, a nitrone was observed, formed by a direct attack of the carbanion at the nitro nitrogen atom, Scheme VII/5 [12],... 

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