Development of Iridium-Complex-Catalyzed Highly Selective Organic Synthesis

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Much less attention has been paid to iridium complex-catalyzed reaction. The aim of this research project is to develop iridium complex-catalyzed highly selective reaction. We have studied the carbonylation of allylic phosphates and cross [2+2+2] cycloaddition of two different monoynes.1. Carbonylation of Allylic Phosphates[Ir(cod)Cl]_2 with a ligand such as P(2-furyl)_3, PPh_2C_6F_5 or AsPh_3 showed high catalytic activity for the carbonylation of allylic phosphates in the presence of alcohols to give the corresponding β,γ-unsaturated esters. The carbonylation of diethyl (E)-3-phenyl-2-opropenyl phosphate in the presence of EtOH under an initial carbon monoxide pressure of 40 kg/cm^2 at 100℃ gave ethyl (E)-4-phenyl-3-butenoate in 90% yield. No (Z)-isomer was obtained. The carbonylation of 2-alkenyl diethyl phosphates in the presence of EtOH gave a mixture of ethyl (E)-and (Z)-3-alkenoate. The stereochemistry of the starting material was lost by syn-anti isomerization of the π-allyl iridium intermediate prior to the insertion of carbon monoxide into the iridium-carbon bond.2. Highly selective cross [2+2+2] addition of two different monoynesHighly selective cross [2+2+2] addition of two different monoynes is achieved by using a catalytic amount of [Ir(cod)Cl]_2 and ligand. Ligand had a considerable effect on the reaction. When 1,2-bis(diphenylphosphino)ethane was used, two molecules of dimethyl acetylenedicarboxylate (DMAD) reacted with one molecule of a monoyne to give the 2:1 coupling product. When 1,2-bis(dipentafluorophenylphosphino)ethane was used instead of dppe, one molecule of DMAD reacted with two molecules of a monoyne to give the 1:2 coupling product.