Reactions of readily available and stable 1-(α-alkoxyalkyl)benzotriazoles type 9a,b and 10a–d with a variety of silyl enol ethers 11 or 1,3-dicarbonyl compounds 13 give the expected ketones 12a–l (60–92%), β-keto esters 14a,b (62–67%), and malonates 14c,d (79–88%) in which a tetrahydrofuran or tetrahydropyran moiety has been introduced at the α position. 1-(Benzotriazol-1-yl)alkyl esters 7 are converted by cyanide anion into cyanohydrin esters 15a–i (55–98%).