Survey of Laboratory Methods

Ethynylation and Alkynylation of Carbonyl Compounds 1. Survey of Laboratory Methods 

In the industrial manufacture of important starting compounds such as HteCCH2OH, HCaCCH(CHg)OH, and HOCH CsCCI OH, high pressure techniques are employed using alkali hydroxides or copper acetylide as catalyst. For extensive reviews on the alkynylation processes the reader is referred to the book [8] and review of Ziegenbein [6]. 

The general scheme for preparation in the laboratory has a number of alternatives, the choice of a particular method being determined by the availability of the starting acetylene, r CsCH, the desired scale of the preparation (e.g. a few millimoles, 100 mmolar, 1 molar or more) and a number of other factors. The most versatile method, suitable for working on scales varying from a few mmoles to -0.5 mole, is the reaction of a lithium alkynylide with a carbonyl compound in THF(-hexane)  

Reduced yields of acetylenic carbinols are often caused by deprotonaiion of the carbonyl compound  

In the Favorski reaction [8], etbyne is coupled with a carbonyl compound in the presence of powdered alkali hydroxide suspended in an organic solvent, in which the acetylene has good solubility. Some acetylenic carbinols, derived from ketones, can be obtained in high yields by introducing acetylene at atmospheric pressure. The active intermediate possibly is a metal acetylide formed in low concentration. 

---