TUNGSTEN CARBONYL-INDUCED CYCLIZATIONS OF ALKYNYL ALCOHOLS TO DIHYDROPYRANYLIDENE CARBENES AND ALPHA-STANNYL DIHYDROPYRANS

Reaction of 1-alkyn-5-ols with tetrahydrofuran-tungsten pentacarbonyl induces cyclization to the corresponding tungsten dihydropyranylidene carbenes. These carbenes can be converted into alpha-stannyl dihydropy rans upon reaction with tributyltin triflate and triethylamine. This s trategy provides the first general preparation of six-membered ring ox acarbenes of the group VI metals, and a novel synthesis of alpha-stann yl dihydropyrans from acyclic compounds. Copyright (C) 1996 Elsevier S cience Ltd