Gyongshik Won

The effects of catalyst composition on the catalytic production of dimethyl carbonate

Abstract The synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of MeOH has been studied in the presence of various catalyst systems. The effect of catalyst composition on the catalytic activity and product composition is investigated. A three-component catalyst system composed of PdCl 2 (PPh 3 ) 2 , Cu(OMe) 2 and Me 4 NCl shows synergy effects in terms of the MeOH conversion (26%) and DMC selectivity (95%). The reaction performed in the presence of a single-component catalyst PdCl 2 (PPh 3 ) 2 produces dimethoxy methane (DMM) as a major product with selectivity over 90%, while the addition of Me 4 NCl or Cu(OMe) 2 to PdCl 2 (PPh 3 ) 2 results in the increase of DMC selectivity from 2% to 60%.

Diastereocontrolled synthesis of cis-olefins by selective C–C bond formation between alkyl and alkynyl groups coordinated to “Ir(CHCHPPh3)(CO)(PPh3)2”

cis,cis-1,4-Dipropenylbenzene (cis,cis-p-C6H4(CHCHCH3)2, cis-DPB) and cis,cis,cis-1,3,5-tripropenylbenzene (cis,cis,cis-m,m-C6H3(CHCHCH3)3, cis-TPB) are obtained in high yields by reactions of di- and tri-nuclear alkyl–alkenyl–alkynyl iridium(III) compounds, [p-C6H4(CC–Ir(CH3)(CHCHPPh3)(CO)(PPh3)2)2]2+1 and [m,m-C6H3(CC–Ir(CH3)(CHCHPPh3)(CO)(PPh3)2)3]3+3 with HCl. The reaction of the mono-nuclear alkyl–alkenyl–alkynyl iridium(III) complex, [Ir(CH3)(CHCHPPh3)(CC-p-C6H4CH3)(CO)(PPh3)2]+7a with DCl selectively gives cis-CD3CDCD(p-C6H4CH3) 8a-d5 while two isomers, cis-C6H5CD2CDCD(p-C6H4CH3) 8b-d4 and cis-C6H5CDCDCD2(p-C6H4CH3) 8b′-d4 are obtained from the reaction of [Ir(CH2Ph)(CHCHPPh3)(CC-p-C6H4CH3)(CO)(PPh3)2]+7b with DCl. Plausible reaction pathways containing the initial attack of H+ on the β-carbon of the alkynyl ligands to produce cis-alkenyl complexes that give η2-allene complexes are suggested for the selective and diastereocontrolled C–C bond forming reactions between alkyl and alkynyl groups to give cis-olefins, 8, cis-DPB, and cis-TPB.