RUTHENIUM COMPLEX-CATALYZED CARBONYLATION OF ALLYLIC COMPOUNDS

Allylic alkyl carbonates are carbonylated under 40 atm of carbon monoxide at 100-120 degrees C in the presence of a catalytic amount of Ru-3(CO)(12)/1,10-phenanthroline to give alpha,beta- or beta,gamma-unsaturated esters in good to high yields. For example, cinnamyl methyl carbonate afforded the corresponding beta,gamma-unsaturated esters, methyl trans-4-phenyl-3-butenoate (1). in 93% yield. The regioselectivity in the carbonylation of crotyl methyl carbonate is unusual and it depends on the carbon monoxide pressure. The more sterically hindered carbon (gamma-carbon) is predominantly carbonylated at 20-50 atm. When the reaction of cinnamyl methyl carbonate was performed at elevated temperature (150 degrees C) without 1,10-phenanthroline, the dimer of 1, dimethyl 3-benzyl-2-(trans-2-phenylvinyl)glutarate, was obtained in 56% yield. In the presence of secondary amines, allylic alkyl carbonates were carbonylated mainly at alpha-carbon to give alpha,beta- or beta,gamma-unsaturated amides in high yields.