Highly enantioselective additions of diethylzinc to aldehydes using 2-triflamido-methyl-2'-hydroxy-1,1'- binaphthyl

[reaction: see text] A new N-triflated amino alcohol-titanium catalyst was designed for the asymmetric ethylation of aldehydes. This binaphthyl-based sulfonamido alcohol ligand shows uniformly high yield and enantioselectivity in the diethylzinc additions of aromatic, aliphatic, and unsaturated aldehydes.     

Enantioselective additions of diphenylzinc to aldehydes using chiral pyrrolidinylmethanol derivatives as catalysts

The enantioselective addition of diphenylzinc to aldehydes using a series of chiral ligands derived from (S)-proline afforded secondary alcohols in high yields and with high enantiomeric excesses of up to 92.6%. The configuration of the secondary alcohol enantiomer obtained was found to be dependent on the catalyst used.     

Chiral zinc amidate catalyzed additions of diethylzinc to aldehydes

A series of bifunctional spiro ligands bearing “carboxamide–phosphine oxide” groups and ethylzinc carboxamidates from these ligands as catalysts for Et₂Zn additions to aldehydes were reported. Excellent yields were obtained with moderate ee′s in Et₂Zn additions to benzaldehyde derivatives, implying effectiveness of our newly designed catalytic structures as well as mediocre stereocontrol by these chiral ligands. Possible transition states were suggested based on the crystal structures of two ligands.     

Chiral ferrocenyl amino alcohols for enantioselective additions of diethylzinc to aldehydes

Optically active ferrocenyl amino alcohols have been prepared from commercially available l-alaninol, l-leucinol and l-valinol. They have been utilized as chiral ligands in the catalytic addition of diethylzinc to aldehydes. The influence of the substituents on the stereogenic centers of the ligand has been studied. Enantioselectivities up to 95% have been obtained.     

Enantioselective addition of diethylzinc to aldehydes catalyzed by optically active 1,4-aminoalcohols

Enantioselective addition reactions of diethylzinc to aldehydes were performed by catalytic reactions with chiral 1,4-aminoalcohols. Optically active 1,4-aminoalcohols were synthesized from (+)-camphor and (−)-fenchone through four steps involving iodine-mediated lactonization of 3-hydroxy acids.     

Syntheses of novel chiral sulfinamido ligands and their applications in diethylzinc additions to aldehydes

A novel class of sulfinamido alcohol ligands 1-6 was synthesized from (S)-tert-butanesulfinamide. These ligands showed excellent catalytic activities and enantiomeric selectivities in asymmetric additions of diethylzinc to aromatic aldehydes.     

Enantioselective addition of diethylzinc to aldehydes in the presence of chiral aprotic ligands

Optically active amino thiocyanate derivatives of (−)-norephedrine were found to act as effective aprotic ligands for enantioselective addition of diethylzinc to aldehydes. This reaction provided optically active secondary alcohols with ee up to 96%.     

Enantioselective addition of diethylzinc to aldehydes using immobilized chiral BINOL–Ti complex on ordered mesoporous silicas

A chiral (S)-BINOL ligand has been covalently grafted on ordered mesoporous silicas—MCM-41 and SBA-15 and the resulting inorganic–organic hybrid materials used as chiral auxiliaries in Ti-promoted enantioselective addition of diethyl zinc to aldehydes under heterogeneous conditions. These heterogeneous catalysts showed promising activity and enantioselectivity. The catalyst having a larger pore diameter with capping of free silanol moiety with trimethylsilyl (TMS) group was found to be more active with enantioselectivities up to 81% being achieved. The catalyst worked well up to three cycles with retention of enantioselectivity after washing with 10% HCl in methanol.     

Enantioselective addition of diethylzinc to aldehydes in the presence of chiral hydrazone and imine ligands

Optically active hydrazone and imine were found to act as effective ligands for enantioselective addition of diethylzinc to aldehydes. This reaction provided optically active secondary alcohols with ee up to 71%.     

Enantioselective addition of diethylzinc to aryl aldehydes catalyzed by novel chiral imino alcohol ligands

The enantioselective alkylation of aryl aldehydes by diethylzinc in the presence of catalytic amounts of several novel chiral imino alcohol ligands, synthesized from the reaction of (R)-2-amino-1-butanol with aromatic aldehydes, was studied. The influence of temperature and ligand structure was investigated and enantioselectivity up to 81% was obtained.     

α-Hydroxy carboxylic acids as ligands for enantioselective diethylzinc additions to aromatic and aliphatic aldehydes

The first examples of the enantioselective titanium-mediated diethylzinc additions to aromatic and aliphatic aldehydes catalyzed by optically active α-hydroxy acids are presented. The reactions proceed with very good yield and good asymmetric induction. Enantioselectivities up to 90% are obtained depending on ligand and aldehyde used. A stereochemical model for the reaction is proposed.     

Enantioselective addition of diethylzinc to aldehydes catalyzed by 5-cis-substituted proline derivatives

5-Cis-substituted prolinols, prolinamines, and prolinamine sulfonamides proved to be efficient ligands for the enantioselective addition of diethylzinc to aldehydes, providing up to 99% ee. The sense of asymmetric induction can be controlled by the nature of the exocyclic functional group (CPh₂OH vs. CH₂NHR vs. CH₂NHSO₃R). The additional 5-cis substituent exerts a strong beneficial effect on the chirality transfer since it rigidifies the catalyst structure. The stereochemical outcome of the reactions is discussed in detail on the respective transition states.     

Enantioselective Michael additions of aldehydes to nitroalkenes catalyzed with ionically tagged organocatalyst

Enantioselective organocatalytic Michael additions affords useful building blocks for many biologically and medicinally relevant compounds. Ionically-tagged diphenylprolinol silyl ether efficiently catalyzes several Michael additions of aldehydes to nitroalkenes in ionic liquids. The Michael additions work well in ionic liquids; yields up to 95% and enantioselectivities up to 95% ee were achieved. Furthermore, in some cases, the catalytic system was reusable.      

Enantioselective addition of diethylzinc to aromatic aldehydes catalyzed by C2-symmetric chiral diols

Optically pure C₂-symmetric diols have been synthesized with moderate yields in a straightforward manner, and are used as catalysts in the enantioselective alkylation of aromatic aldehydes with diethylzinc. The addition of diethylzinc to benzaldehyde and sterically hindered 1-naphthaldehyde was achieved with excellent enantioselectivities (97–99% ee) under catalysis with (1R,2R)-1,2-bis(3,5-dibromophenyl)-ethane-1,2-diol and (1R,2R)-1,2-bis(3,5-diphenylphenyl)-ethane-1,2-diol.     

Enantioselective phenyl transfer to aldehydes using 1,1′-bi-2-naphthol-3,3′-dicarboxamide as chiral auxiliary

N,N,N′,N′-Tetra-n-butyl-BINOL-3,3′-dicarboxamide 5d was found to promote phenyl transfer from ethylphenylzinc to both aromatic and aliphatic aldehydes with high enantioselectivity up to 96% ee in tert-butyl methyl ether.     

Enantioselective addition of diethylzinc to aryl aldehydes catalyzed by 1,2,3,4-tetrahydroisoquinoline β-amino alcohol

<正>A highly effective,new chiral 1,2,3,4-tetrahydroisoquinoline catalyst 1 for the diethylzinc addition to aryl aldehydes has been investigated.Using 10 mol%of this chiral catalyst,secondary alcohols can be obtained in up to 87%yield and 99.5%ee under mild conditions.     

Stereocontrolled enantioselective addition of diethylzinc to aldehydes using new chiral aminoalcohols

The new chiral β-aminoalcohols of indolinylmethanols ( 1 ) and their reduced derivatives ( 2 ) were synthesized from (S)-indoline-2-carboxylic acid. Both (R) and (S) enantiomers of the optically active secondary alcohols have been successfully obtained in high enantiomeric excess from the stereoselective addition of diethylzinc to the aldehydes catalyzed by the chiral aminoalcohols ( 1 and 2 ). The sense of the asymmetric induction and the degrees of enantioselectivities turned out to be highly dependent on the structure of the catalysts: The presence of the catalyst 1 afforded the (S)-configuration of the corresponding alcohols; on the other hand, the presence of 2 afforded the (R)-configuration of the alcohols in high enantiomeric selectivity.     

Structural optimization of enantiopure 2-cyclialkylamino-2-aryl-1,1-diphenylethanols as catalytic ligands for enantioselective additions to aldehydes

The structural optimization of a family of modular, enantiopure beta-amino alcohol ligands with a common 2-amino-2-aryl-1,1-diphenylethanol skeleton, whose stereogenicity was introduced through the Jacobsen epoxidation of 1,1-diphenyl-2-arylethylenes, has led to the identification of a small set of optimal catalysts with enhanced activity and enantioselectivity in the addition of alkylzinc and arylzinc reagents to aldehydes. Criteria for the discrimination between apparently analogous, highly enantioselective ligands are proposed.     

Enantioselective addition of diethylzinc to aldehydes induced by a new chiral Ti(IV) catalyst

A new chiral titanium reagent, derived from optically active trans-1,2-dicamphorsulfonamidocyclohexane 2a and Ti(OⁱPr)₄, was found to promote the enantioselective addition of diethylzinc to various aldehydes giving rise to the corresponding alcohols in high yields with moderate to high selectivity.     

Synthesis of 1,1'-binaphthyls by photo-dehydro-Diels-Alder reactions

1,1'-Binaphthyls are prepared by a conceptually novel approach based on the photo-dehydro-Diels-Alder reaction.