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
novel intramolecularhydroacylation of 5- and 6-alkynals leading to alpha-alkylidenecycloalkanones was accomplished by using cationic a rhodium(I)/BINAP complex. For all cyclizations described, a single (E)-olefin isomer was obtained. At elevated temperature, hydroacylation and double bond migration of 5- and 6-alkynals proceeded in a one-pot reaction to give cycloalkenones. An intramolecular hydroacylation