Intramolecular electroreductive cyclization of heteroatom-containing non-conjugated enones and ynones

Electroreduction of non-conjugated enones and ynones containing a sulfur or a nitrogen atom in the connecting chains brought about regio- and stereoselective intramolecular cyclization to give the corresponding heteroatom-containing cyclic alcohols in moderate to good yields. These materials may be useful synthetic intermediates of biologically active compounds. Some decrease in stereoselectivity on intramolecular cyclization of nitrogen-containing non-conjugated enones is rationalized by postulating that the lone pair electrons of the nitrogen atom repel the negative charges on the oxygen atoms and the alkyl carbon atoms of the cyclized anion radical intermediates.