Propynoate esters conjugate additions

Cuprates of the type Li CuR + i, where > 1, react with the carbonyl group of propynoate esters rather than give the conjugate addition product 61). Extension of the reaction of propynoate esters to vinylcopper compounds and allylcopper compounds affords a stereospecific synthesis of 1,3- and 1,4- dienes, respectively 64, 205). 

---