The Framework Scope and Limitations

As indicated by the conversion of 70 to 71, the electroreductive cyclization reaction provides as excellent method for the assembly of the bicyclo[3.2.1]oc-tane ring system. Several additional examples are portrayed in the following equations. In general, the use of an unsaturated nitrile rather than the corresponding ester is preferred, as this precludes lactone formation, and therefore 

As with any transformation, this methodology is not without limitations. For example, the y-hydroxy unsaturated ester 80 failed to undergo the desired cyclization [43]. Instead, elimination occurred, presumably leading to the extended enolate 82 which condenses onto the aldehyde unit to afford the [3.3.0] adduct 83 in a 45% yield. 

Another occasionally troublesome process is related to the tendency of some substrates to preferentially, or competitively, undergo acid-base chemistry [43,44]. Of course, this is not surprising, considering the nature of the putative intermediates. One system where this process diminishes the efficiency of the electroreductive cyclization is that of compound 84. In this reaction, no more 

Another example of a case where acid-base chemistry competes with cyclization is found in efforts to construct an analog of the Corey lactone [45], The enantiomerically pure unsaturated ester 91 was assembled and subjected to the conditions indicated in Eq. (26). In this instance, dimethyl methylmalonate was used as the proton donor to avoid 1,4-addition of the conjugate base to 91. Cyclization afforded a combined 77% isolated yield of the y-hydroxy ester 92 and the lactone 93 the former could be converted to the lactone in the 

Straightforward manner portrayed above. Unfortunately, these materials were accompanied by the formation of the conjugated diene 94, a substance which undoubtedly arises via the intervention of acid-base chemistry, leading to yS-elimination of the silyloxy unit. 

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