Triphenylphosphine-Catalyzed Isomerisation of Propargyl Bromide to 1-Bromopropadiene

Abstract

Pure bromopropadiene, BrCH=C=CH₂ has been obtained by isomerisation of propargyl bromide in the presence of catalytic amounts of triphenylphosphine.

Notes

Yield relating to the conversion of propargyl bromide.

No isomerisation was observed in CDCl₃. Treatment of 2 with triphenyl-phosphine in benzene under the given conditions did not result in the formation of 1.

Isomerisation of 1 to 2 was also observed with tricyclohexylphosphine. Without added phosphine no isomerisation was detected if a benzene solution of 1 was heated for 48 h.

a) 3-Bromo-3-phenyl-l-propyne and 3-bromo-hex-1-yne show a sluggish reaction with triphenylphosphine. No defined products could be isolated

the restriction of the reaction to non-polar solvents indicates the importance of a contact ion pair for the isomerisation process;