Metalation of Alkynes. 1. Effect of Alkyne Structure on the Rate of Acetoxymercuration

Article abstract of DOI:10.1021/jo00372a007

The rates of Hg(OAc)2 addition to symmetrically and unsymmetrically substituted alkynes (4-octyne, 2-heptyne, 2-nonyne, 1,4-dimethoxy-2-butyne, 1,4-diacetoxy-2-butyne, methyl 2-octynoate, 1-phenylpropyne, 1-phenyl-1-pentyne, methyl 3-phenylpropynoate, and diphenylethyne) were measured in acetic acid.Activation parameters were determined for representative substrates.The corresponding vinylacetoxymercury acetates were isolated under preparative conditions.The rate law was overall second order, first order in both alkyne and mercuric acetate.Alkylacetylenes are more reactive than phenylacetylenes, and the reaction rate is decreased by electron-withdrawing substituents.The data are the first kinetic evidence for an associative process characterized by the electrophilic attack of mercuric acetate to the triple bond.