Pd-catalyzed asymmetric synthesis of allylic tert-butyl sulfones and sulfides: Kinetic resolution of the allylic substrate by a chiral Pd-complex
摘要:
The acyclic and cyclic allylic tert-butyl sulfones 3, ent-3, 11a, 11b and 15a-c of 89-98% ee were synthesized in 40-92% yield by a Pd-catalyzed reaction of the respective allylic acetates and carbonates rac-1a, rac-1b, rac-10a, rac-10b and rac-14a-c with LiO(2)St-Bu in the presence of the chiral ligands 2a, ent-2b and 12. Formation of the n-butyl sulfones 13a and 13b of 95% ee was observed. Reactions of rac-1a and 1b/ent-1b with LiO(2)St-Bu in the presence of 2a and ent-2b, respectively, in THF under heterogeneous conditions were accompanied by a kinetic resolution of the allylic substrates. The faster reacting allylic substrate and the preferentially formed sulfone had the same absolute configuration. The allylic tert-butyl sulfide 17 of 92% ee was obtained in 63% yield by the Pd-catalyzed reaction of rac-1b with Me(3)SiSt-Bu in the presence of ent-2b. (C) 1998 Elsevier Science Ltd. All rights reserved.
decomplexation. Concurrently, the preparation of AMPP* ligands with a P-chirogenic phosphinite moiety was performed by N → O phosphinyl migration of aminophosphines borane by heating at 50 °C with DABCO and then reaction with chlorophosphines. AMPP* ligands were studied in palladium-catalyzed asymmetricallylicalkylations, leading to enantioselectivities from 91% (R) to 95% ee (S). X-ray crystallographic data
Pd2 decomposes into molecular species. In addition, the high enantioselective systems, Pd1 and Pd3, are only active for a substrate containing phenyl groups. Concerning the catalytic behaviour of the corresponding molecular systems, palladiumcomplexes coordinated to ligands 1 or 3, gave excellent asymmetric inductions, but an analogous catalyst accommodating ligand 2, was not found selective.
Chiral allylic esters, such as (R)-1,3-diphenyl-2-propenyl acetate (R)-2a, were synthesized by kinetic resolution in a palladium-catalyzedasymmetricallylicalkylationusing N-aryl indoline type C–N bond axially chiral aminophosphines (S)-1 as ligands.
Palladium nanoparticles (4 nm, fcc) were prepared through decomposition of [Pd2(dba)3] by H2 in the presence of a chiral xylofuranoside diphosphite. These particles catalyze the allylicalkylation of rac-3-acetoxy-1,3-diphenyl-1-propene with dimethyl malonate leading to an almost total conversion of the (R) enantiomer and almost no reaction with the (S). This gives rise to 97% ee for the alkylation
Kinetic Resolution in Palladium-Catalyzed Asymmetric Allylic Alkylations by a P,O Ligand System
作者:Scott R. Gilbertson、Ping Lan
DOI:10.1021/ol0161256
日期:2001.7.1
[GRAPHICS]Through the investigation of peptide-based phosphine oxazoline ligands, a simple P,O ligand system was developed. This system provides palladium complexes that are capable of a very high degree of kinetic resolution of 1,3-diphenylprop-2-enyl acetate. The isolated palladium complex was synthesized, characterized, and determined to be an effective procatalyst.