Cyclization reactions of 2-alkynylbenzyl alcohol and 2-alkynylbenzylamine derivatives promoted by tetrabutylammonium fluoride

The regioselectivity of the cyclization reaction of 2-ethynylbenzyl alcohol and 2-ethynylbenzylamine derivatives promoted by TBAF was investigated. Si x-membered ring derivatives were obtained from the compounds, which have a butyl group on the triple bond. Whereas five-membered ring products were af forded from the substrates having hydrogen or aromatic substituents. on the acetylene moiety. It was also concluded that both the tetrabutylammonium c ation and fluoride anion were essential for the cyclization. Thus, the actu al mechanism and catalytic cycle were also suggested. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.