In Situ Generation of 1-Propyne: A Useful Introduction of 1-Propyne on Unsaturated Halogenated Compounds through the Sonogashira Reaction

Reaction of (E/Z)-1-bromopropene with exactly 1.42 equivalents of nBuLi followed by addition of water produces in situ a THF solution of propyne. Addition of a vinylic or aromatic halogenated substrates, Pd(PPh3)2Cl2, CuI and an amine to this solution give high yield of the corresponding coupling product bearing a propyne moiety. This practical procedure avoids the use of expensive and inflammable propyne gas which need a special apparatus for bubbling it into the reaction flask.