ALKYNYLHALOCARBENES - 3 - SYNTHESIS OF 2-(ALK-1-YNYL)OXIRANES FROM 1,1-DICHLOROALK-2-YNES AND 3-SUBSTITUTED 3-BROMO-1,1,1-TRICHLOROPROPANESUNDER THE ACTION OF POTASSIUM TERT-BUTOXIDE IN THE PRESENCE OF ALKALI-METAL ALKOXIDES

(Alk-1-ynyl)chlorocarbenes (3), generated from 1,1-dihaloalk-2-ynes an d 3-substituted 3-bromo-1,1,1-trichloropropanes under the action of (B uOK)-O-t in THF at 20 degrees C, react with excess alkali metal alkoxi de 4 to give 3-substituted 2-(alk-1-ynyl)oxiranes (6) in 26-78%; yield s, most likely as a result of insertion of carbene 3 into the alpha C- H bond of alkoxides 4 and subsequent cyclization of the resulting 1-su bstituted 2-chloro-2-(alk-1-ynyl)etoxides. The yields of oxiranes 6 de pend on the nature of the alkali metal used to prepare alkoxides 4 and on the method employed for the preparation of the latter.