عنوان

Novel palladium(II) catalysts for asymmetric synthesis

TLpq304370732

انگلیسی

Novel palladium(II) catalysts for asymmetric synthesis

[Thesis]

A. K. El-Qisairi

P. M. Henry

Loyola University Chicago

1997

171

Ph.D.

Loyola University Chicago

1997

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 usd\{usd(R)-DMPAusd\}usd, (S)-(+)-neomenthyl diphenylphosphine usd\{usd(S)-NMDPPusd\}usd and the bidentate ligands, (1R,2R)-()-1,2-diaminocyclohexane usd\{usd(1R,2R)-DACHusd\}usd, (+)-2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis-(diphenylphosphino)butane usd\{usd(+)-DIOPusd\}usd, ()-2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis-(diphenylphosphino)butane usd\{(-usd)-DIOPusd\}usd and (S)-()-2,2-bis(diphenylphosphino)-1,1-binaphthyl usd\{usd(S)-BLNAPusd\}usd were prepared and characterized by H-NMR, C-NMR, P-NMR, IR spectroscopy and elemental analysis. The bidentane ligands bridged the two Pd(II)'s. The oxidation of usd\alphausd-olefins with these catalysts were studied under conditions of low (Cl) and high (CuCl2). 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 ()-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-usd\alphausd-naphthyl ether indicated that only the 38 isomer is formed. The yields were very high (>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 CuCl2 gave mainly usd\alphausd-hydroxy ketones. The % ee of the usd\alphausd-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%.

Chemistry

Chemistry

Organic chemistry

Pure sciences

A. K. El-Qisairi

P. M. Henry

p

[Thesis]

276903

a

Y