Alkylative cyclization, carbon-nitrogen systems

In the latter example, cyclization occurs exclusively to the carbonyl carbon rather than with nucleophilic displacement of chloride at the a-carbon. Intramolecular alkylation of nitrogen does occur in other systems the 3-chloropropylsulfonylhydrazide (194), for example, ring closes to give the 1,2,3-thiadiazine dioxide (195) on treatment with base (62JPR(19)56). 

A possible mechanism for the cyclization is indicated in A- C. It will be noted that the stereochemistry of the product (CCCXCI) thus formed is that of the natural series of alkaloids at Ci4 This results from the fact that the amino group of CCCXC must be equatorial since its adjacency to a ketone allows it to epimerize to the more stable configuration after its formation. The alkylation reaction can obviously form the new carbon-carbon bond only cis to the nitrogen atom, and the result is a cis decalin system in CCCXCI, even though the precursor (CCCXC) undoubtedly has a trans decalin system. 

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