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

Article abstract of DOI:10.1246/bcsj.72.303

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