Pd(II) allyl and Pd(0) olefin complexes containing the configurationally labile ligand 1,2-bis-[4,5dihydro-3H-dibenzo[c-e]azepino]ethane were studied as models for intermediates in Pd-catalyzed allylic alkylations. According to NMR and DFT studies, the ligand prefers C-s conformation in both eta(3)-1,3-diphenylpropenyl and eta(3)-cyclohexenyl Pd(II) complexes, whereas in Pd(0) olefin complexes it adopts different conformations in complexes derived from the two types of allyl systems in both solution and, as verified by X-ray crystallography, in the solid state. These results demonstrate that the Pd complex is capable of adapting its structure to the reacting substrate. The different structural preferences also provide an explanation for the behavior of 1,3-diphenyl-2-propenyl acetate and 2-cyclohexenyl acetate in Pd-catalyzed allylic alkylations using pseudo-C-2 and pseudo-C-s symmetric ligands.
Influence of Steric Symmetry and Electronic Dissymmetry on the Enantioselectivity in Palladium-Catalyzed Allylic Substitutions
摘要:
Chiral P,N-ligands with pseudo-C-2 and pseudo-C-s symmetry based on chiral pyrrolidine and phospholane rings or on dinaphthatodihydroazepino and dinaphthatodihydrophosphepino moieties were prepared and assessed in the palladium-catalyzed allylic substitutions of allylic acetates. Higher selectivity was achieved with pseudo-C-2-symmetric ligands based on the binaphthyl skeleton than with the analogous C-2-symmetric P,P- and N,N-analogues. Pseudo-C-2-type ligands had properties superior to those of pseudo-meso-type ligands when 1,3-diphenyl-2-propenyl acetate was used as a substrate, whereas the reverse situation was found for 3-cyclohexenyl acetate. Chirally flexible ligands, prepared by substitution of one of the rigid binaphthyl skeletons for a flexible biphenyl system, were found to induce chirality to the same extent as a 1:1 mixture of the rigid ligands.
binaphthalene-based tertiary amines have been used for the asymmetric aziridination of chalcone, providing N-unprotected aziridines with ee values of up to 43%. A chiral hydrazinium salt has been isolated for the first time and shown to provide similar yield and enantioselectivity to the in situ process in reaction with chalcone.
原位衍生自许多对映异构纯的联萘叔胺的胺已用于查耳酮的不对称氮丙啶化,提供 N-未保护的氮丙啶,其 ee 值高达 43%。首次分离出手性肼盐,并显示出与原位与查耳酮反应过程相似的产率和对映选择性。
Chiral catalysis of additions of alkyllithiums to aldehydes
作者:Jean Paul Mazaleyrat、Donald J. Cram
DOI:10.1021/ja00405a052
日期:1981.7
Synthesis and resolution of axially chiral C2-symmetric 1,1′-binaphthyl-substituted tetramethylethylenediamines
作者:Jean-Paul Mazaleyrat
DOI:10.1016/s0957-4166(97)00301-7
日期:1997.8
The axially chiral TMEDA derivatives 1 and 2 in which tetramethylethylene-diamine is substituted respectively by one and two 1,1'-binaphthyl units at their 2,2'positions, are of interest as chiral catalysts. Experimental details of their preparation in enantiomerically pure form are given. Two different routes have been followed, involving alkylation of both N,N-dimethyl ethylenediamine and ethylenediamine by 2,2'bis-(bromomethyl)-1,1'-binaphthyl either enantiomerically pure as prepared from resolved 1,1'-binaphthyl-2,2'-dicarboxylic acid or racemic, the resulting racemic diamines 1 and 2 being then resolved with dibenzoyl-tartaric acid. (C) 1997 Elsevier Science Ltd.
Shi, Min; Itoh, Nobuhiro; Masaki, Yukio, Journal of Chemical Research, Miniprint, 1996, # 8, p. 1946 - 1955