Ring closure Reformatsky

The influence of a Lewis acid in favouring the ring closure was confirmed by the use of a catalytic amount of CpiTiCL in imino-Reformatsky reactions with a-bromoesters, -bromocrotonates and a-bromomethylacrylates the corresponding cis /9-lactams were obtained in excellent yields in THF at rt129. 

There are many odier named reactions that follow die same general features but differ as to die type of enolate or the carbon electrophile. These include the Reformatski reaction, the Darzens reaction, and the Dieckmann ring closure. They were in widespread use for many years and were named as a convenient way to characterize the reactants employed and type of product which results. The reason that diere are so many variations on the same theme is that control of the reaction products depends on die ability to generate a particular enolate nucleophile and... 

The first step is considered to involve the condensation of the Reformatsky reagent with benzonitrile to yield the Zn-salt 5. C-alkylation by bromoacetate, followed by ring closure, is believed to lead to the hitherto elusive key intermediate 6A, a pyrrolinone ester. Condensation with a second molecule of benzonitrile and subsequent cyclization of intermediate 7, which could be isolated and was also mentioned by Famum, finally affords the DPP 2. 

---