Die Addition von Säuren an Alkinderivate mit Push‐pull‐Gruppen ,

The addition of proton acids as HF, HCl, HBr, HOAc and phenol to alkyne‐derivatives of the type (CH 3 ) 2 NCCCOR( 1 ) yielding the adducts 2 to 6 is investigated. The stereochemical course of the reaction is mainly influenced by the structure of the alkyne 1 . Kinetic investigations show that the rate of the third‐order‐reaction increases from 1 a (RH) to 1 b (R CH 3 ) and 1 c (R OCH 3 ) and decreases drastically in polar solvents. According to these results a reaction mechanism is outlined and discussed.