87241-23-4Relevant articles and documents
Ruthenium-catalyzed tandem-isomerization/asymmetric transfer hydrogenation of allylic alcohols
Slagbrand, Tove,Lundberg, Helena,Adolfsson, Hans
, p. 16102 - 16106 (2015/01/09)
A one-pot procedure for the direct conversion of racemic allylic alcohols to enantiomerically enriched saturated alcohols is presented. The tandem-isomerization/ asymmetric transfer hydrogenation process is efficiently catalyzed by [{Ru(p-cymene)Cl2}2] in combination with the a-amino acid hydroxyamide ligand 1, and performed under mild conditions in a mixture of ethanol and THF. The saturated alcohol products are isolated in good to excellent chemical yields and in enantiomeric excess up to 93%.
Insights into the asymmetric heterogeneous catalysis in porous organic polymers: Constructing A TADDOL-Embedded chiral catalyst for studying the structure-activity relationship[ ]
An, Wan-Kai,Han, Man-Yi,Wang, Chang-An,Yu, Si-Min,Zhang, Yuan,Bai, Shi,Wang, Wei
supporting information, p. 11019 - 11028,10 (2014/12/09)
Construction of porous organic polymers (POPs) as asymmetric catalysts remains as an important but challenging task. Herein, we exploit the "bottom-up" strategy to facilely synthesize an α,α, α,α-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL)-based chiral porous polymer (TADDOL-CPP) for highly efficient asymmetric catalysis. Constructed through the covalent linkages among the three-dimensional rigid monomers, TADDOL-CPP possesses hierarchical porous structure, high Brunauer-Emmett-Teller (BET) surface area, together with abundant and uniformly-distributed chiral sites. In the presence of [Ti(OiPr)4], TADDOL-CPP acts as a highly efficient and recyclable catalyst in the asymmetric addition of diethylzinc (Et2Zn) to aromatic aldehydes. Based on the direct observation of the key intermediates, the reaction mechanism has been revealed by solid-state 13C magic-angle spinning (MAS) NMR spectroscopy. In combination with the catalytic testing results, characterization on the working catalyst provides further information for understanding the structure-activity relationship. We suggest that the catalytic activity of TADDOL-CPP is largely affected by the structural rigidity, cooperative catalysis, local chiral environment, and hierarchical porous framework. We expect that the information obtained herein will benefit to the designed synthesis of robust POP catalysts toward practical applications.
(R)-(+)-N-methylbenzoguanidine ((R)-NMBG) catalyzed kinetic resolution of racemic secondary benzylic alcohols with free carboxylic acids by asymmetric esterification
Nakata, Kenya,Shiina, Isamu
supporting information; experimental part, p. 7092 - 7096 (2011/11/04)
(R)-(+)-N-Methylbenzoguanidine ((R)-NMBG) was found to function as an efficient acyl-transfer catalyst for the kinetic resolution of racemic secondary benzylic alcohols in the presence of achiral carboxylic acids and pivalic anhydride. The use of a tertiary amine in this reaction is not necessary to attain good chemical yields of the products. It was determined that diphenylacetic acid could be employed as the most suitable acyl donor for achieving a high enantioselectivity for the kinetic resolution of the racemic secondary benzylic alcohols having normal aliphatic alkyl chains at the C-1 positions. On the other hand, a less-hindered carboxylic acid, such as 3-phenylpropanoic acid, functioned as a better acyl donor for the kinetic resolution of racemic secondary benzylic alcohols having branched aliphatic alkyl chains at the C-1 positions.
Catalytic asymmetric addition of diethylzinc to aldehydes via chiral, non-racemic β-hydroxy and β-methoxy salicylhydrazone catalysts
Banerjee, Sucharita,Ferrence, Gregory M.,Hitchcock, Shawn R.
scheme or table, p. 837 - 845 (2010/11/02)
(1S,2S)-Pseudoephedrine and (1S,2S)-pseudonorephedrine have been converted to their corresponding hydrazines and condensed with either o-salicylaldehyde or 2-hydroxy-1-naphthaldehyde to afford a series of β- hydroxysalicylhydrazones that have been employed in the asymmetric addition of diethylzinc to 2-naphthaldehyde in up to 56% ee. In addition to this, the Ephedra hydrazines were also condensed with the o-hydroxyacetophenone derivative to form related hydrazones. The use of these corresponding hydrazones in the asymmetric addition reaction with the diethylzinc did not yield improved enantioselectivities. Finally, Enders' hydrazine was used as a chiral scaffold for the synthesis of β-methoxysalicylhydrazones. These compounds were employed in the asymmetric addition of diethylzinc to a variety of aromatic aldehydes with enantiomeric excesses as high as 68% ee.
Highly enantioselective arylation of aldehydes and ketones using AlArEt2(THF) as aryl sources
Zhou, Shuangliu,Wu, Kuo-Hui,Chen, Chien-An,Gau, Han-Mou
supporting information; experimental part, p. 3500 - 3505 (2009/09/30)
A series of AlArEt2(THF) (Ar = Ph (la), 4-MeC6H 4 (1b), 4-MeOC6H 4 (1c), 4-Me 3SiC6H4 (1d), 2-naphthyl (le)) were synthesized from reactions of AlEt2Br(THF) with ArMgBr. In CDC13 solution, the 1H NMR spectra showed that AlArEt2(THF) compounds exist as a mixture of four species of formulas of AlAr xEt3-x (THF) (x = 0, 1, 2, or 3). AlArEt2(THF) compounds were found to be superior and atom-economic reagents for asymmetric aryl additions to organic carbonyls. Aryl additions of AlArEt2(THF) to aldehydes catalyzed by the titanium(IV) complex of (R)-H8-BINOL were efficient with a short reaction time of 1 h, affording aryl addition products as exclusive or main products in high yields and excellent enantioselectivities of up to 98% ee. Although ethyl additions to aldehydes occurred in minor extent, this study demonstrates that increasing the amount of AlArEt2(THF) from 1.2 to 1.4 or to 1.6 equiv significantly improved the aryl addition products of up to >99%. On the other hand, asymmetric arylations of AlArEt2(THF) to ketones employing a titanium(IV) catalyst of (S)-BINOL produced optically active tertiary alcohols exclusively in excellent enantioselectivities of up to 94% ee.
Synthesis of a new 1,4-aminoalcohol and its use as catalyst in the enantioselective addition of organozinc to aldehydes
Scarpi, Dina,Galbo, Fabrizio Lo,Guarna, Antonio
, p. 1409 - 1414 (2007/10/03)
The synthesis of a new enantiopure, conformationally constrained 1,4-aminoalcohol is reported, starting from commercially available reagents from the chiral pool. This 1,4-aminoalcohol was used as chiral ligand in the addition of Et2Zn to aldehydes (best ee 98%) and in the synthesis of chiral propargylic alcohols (best ee 70%) by alkynylzinc species.
([2]Paracyclo[2](5,8)quinolinophan-2-yl)carbinols as catalysts for diethylzinc addition to aldehydes: Cooperative effects of planar and central chirality on the asymmetric induction
Ricci, Giacomo,Ruzziconi, Renzo
, p. 1817 - 1827 (2007/10/03)
A systematic study to assess the contribution of planar and central chirality to the asymmetric induction in the diethylzinc addition to aromatic and aliphatic aldehydes has been carried out using planar chiral quinolinophanylcarbinols (Rp)-1 and (Rp)-11 and diastereomeric quinolinophanylcarbinols (Rp,R)- and (R p,S)-5-8, exhibiting both planar and central chirality as catalysts. The stereochemistry of the addition process leading to aryl- or 1-alkylpropanols seems to be mostly controlled by the central chirality. Nevertheless, the planar chirality shows a remarkable cooperative effect on the degree of asymmetric induction, which turns out to be positive or negative depending on the configuration of the stereogenic carbon of the catalyst.
(S)-(-)- and (R)-(+)-4-methyl-2-hydroxymethyl[2]paracyclo-[2](5,8)quinolinophane: Novel N,O-planar chiral catalysts for the enantioselective addition of diethylzinc to aldehydes
Ruzziconi, Renzo,Piermatti, Oriana,Ricci, Giacomo,Vinci, Daniele
, p. 747 - 750 (2007/10/03)
Novel planar chiral N,O-ligands derived from (R)-(+)and (S)-(-)-2,4-dimethyl[2]paracyclo[2](5,8)quinolinophane were synthesized and employed as catalyst in the enantioselective addition of diethylzinc to aromatic aldehydes. On the basis of the ee values, ranging from 30% to 75%, and the configuration of the obtained 1-phenyl-1-propanols a plausible structure of the transition state for the alkylation process of the aldehydes is discussed.
The synthesis of dendritic BINOL ligands and their applications in the enantioselective Lewis acid catalyzed addition of diethylzinc to aldehydes
Fan, Qing-Hua,Liu, Guo-Hua,Chen, Xiao-Min,Deng, Guo-Jun,Chan, Albert S. C.
, p. 1559 - 1565 (2007/10/03)
Novel dendritic chiral BINOL ligands have been synthesized through coupling of MOM-protected 3,3′-dihydroxy-methyl- binaphthol with Frechet-type polyether benzyl bromide dendrons followed by deprotection of the MOM groups using TsOH. These dendritic chira
Addition of Diethylzinc to Aryl Aldehydes Catalyzed by (1S,3S)-N,NI-bis-1,3-Diphenyl-1,3-Propanediamine and its Dilithium Salts: a Mechanistic Rationale Investigation.
Pini, Dario,Mastantuono, Alberto,Uccello-Barretta, Gloria,Iuliano, Anna,Salvadori, Piero
, p. 9613 - 9624 (2007/10/02)
N,NI-bis benzyl substituted 1,3-diamine 1a, synthesized in high optical purity, and the corresponding dilithium salt 1b are used, for the first time, as chiral catalysts in the addition of ZnEt2 to aromatic aldehydes.Both 1a and 1b are able to promete the reaction but the products obtained exhibited low enantiomeric excesses.By 1H NMR and UV-CD investigation, experimental evidences about the structure of some reaction intermediates have been gained: reaction pathway consistent with spectroscopic data, chemical and stereochemical results could be postulated.