| The objective of this project is the development of new asymmetric syntheses by chiral palladium catalysts. Several chiral mono and dipalladium(II) catalysts using the monodentate ligands, (R)-(+)-N,N-dimethyl-1-phenethylamine {dollar}{lcub}{dollar}(R)-DMPA{dollar}{rcub}{dollar}, (S)-(+)-neomenthyl diphenylphosphine {dollar}{lcub}{dollar}(S)-NMDPP{dollar}{rcub}{dollar} and the bidentate ligands, (1R,2R)-({dollar}-{dollar})-1,2-diaminocyclohexane {dollar}{lcub}{dollar}(1R,2R)-DACH{dollar}{rcub}{dollar}, (+)-2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis-(diphenylphosphino)butane {dollar}{lcub}{dollar}(+)-DIOP{dollar}{rcub}{dollar}, ({dollar}-{dollar})-2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis-(diphenylphosphino)butane {dollar}{lcub}(-{dollar})-DIOP{dollar}{rcub}{dollar} and (S)-({dollar}-{dollar})-2,2{dollar}spprime{dollar}-bis(diphenylphosphino)-1,1{dollar}spprime{dollar}-binaphthyl {dollar}{lcub}{dollar}(S)-BLNAP{dollar}{rcub}{dollar} were prepared and characterized by {dollar}sp1{dollar}H-NMR, {dollar}sp{lcub}13{rcub}{dollar}C-NMR, {dollar}sp{lcub}31{rcub}{dollar}P-NMR, IR spectroscopy and elemental analysis. The bidentane ligands bridged the two Pd(II)'s. The oxidation of {dollar}alpha{dollar}-olefins with these catalysts were studied under conditions of low (Cl{dollar}sp-{dollar}) and high (CuCl{dollar}sb2{dollar}). 1-Chloro-2-hydroxyalkanes (38) were the major product with smaller amounts of 2-chloro-1-hydroxyalkane (39). The highest optical yields for the 1-chloro-2-hydroxy-alkanes were obtained when (+)- or ({dollar}-{dollar})-DIOP and (S)-BINAP were used as bridging ligands. Oxidation of allyl ethers to give chiral chlorohydrins could be a valuable new asymmetric synthesis which would be an alternative to procedures involving the Sharpless epoxidation. Our results with allyl phenyl ether and allyl-{dollar}alpha{dollar}-naphthyl ether indicated that only the 38 isomer is formed. The yields were very high ({dollar}>{dollar}90%) and the ee's were in the range of 80-93%.; Oxidation of trans-2-butene and trans-2-pentene with chiral dipalladium(II) catalysts in chloride-free glacial acetic acid gave chiral allylic acetates with ee's of 77-85%. 2-Cyclohexen-1-yl acetate was obtained in a high yield, but the %ee was only 6%.; The oxidation of several ketones by the bimetallic catalyst 27 in the presence of CuCl{dollar}sb2{dollar} gave mainly {dollar}alpha{dollar}-hydroxy ketones. The % ee of the {dollar}alpha{dollar}-hydroxy ketones were in the range of 74%-90%. Since the reaction is an enolization, it would be expected to be acid catalyzed. Methanesulfonic acid was used to accelerate the enolization and the yields did increase dramatically.; Allylic isomerization studies of crotyl alcohol gave chiral 3-buten-2-ol while isomerization of crotyl acetate, crotyl chloride and trans-2-hexenyl acetate gave chiral allylic acetates. The products were obtained in moderate yields (20%-40%). The ee's of the chiral allylic compounds were in the range of 32%-77%. |
