We have developed catalytic isomerizations of 5-alkynals to γ-alkynyl ketones and cyclopent-1-enylketones using [RhP(OPh)3}2]BF4 as a catalyst. Cu(OTf)2 and AgBF4 are also effective catalysts for the formation of γ-alkynyl ketones. The substituents at the 4-positions in 5-alkynals play important roles in the selection of two different isomerization pathways. The first catalytic endo/trans hydroacylation