Reaction of 2-hydroxybenzaldehydes with alkynes, alkenes, or allenes via cleavage of the aldehyde C-H bond using a rhodium catalyst system

2-Hydroxybenzaldehydes smoothly and efficiently react with various internal and terminal alkynes accompanied by cleavage of the aldehyde C-H bond by u sing a rhodium-based catalyst system of [RhCl(cod)](2)/dppf/Na2CO3 [cod = 1 ,5-cyclooctadiene; dppf=1,1'-bis(diphenylphosphino)ferrocene] to give the c orresponding 2-alkenoylphenols in good to excellent yields. The regioselect ivity of the reaction depends on the substituents of acetylene; an oxygen f unction on the propargylic position shows a considerable directing effect. The aldehydes can also react with some alkenes or allenes, such as triethyl vinylsilane and 2-norbornene or 3-methyl-1,2-butadiene and 1,2-nonadienes, in place of alkynes.