Enantioselective Addition of Diethylzinc to Aldehydes Catalyzed by γ‐Amino Alcohols Derived from (+)‐ and (‐)‐α‐Pinene.

Abstract

Alcohols Q 0230Enantioselective Addition of Diethylzinc to Aldehydes Catalyzed by γ-Amino Alcohols Derived from (+)-and (-)-α-Pinene. -Chiral amino alcohols (I) and diamine (II) are prepared and tested as catalysts in the addition reaction of ZnEt2 to aromatic aldehydes. No enantioselective results are observed with (II) whereas on application of the amino alcohols, moderate asymmetric induction is observed. The best enantioselectivites are obtained by use of amino alcohol (Ia). Remarkably, by change of the substituents at the nitrogen from NMe2 or NHBn at compounds (Ia) and (Ib) to NH2 or NHMe at compounds (Ic) and (Id), the direction of enantioselectivity turns from (S) to (R). -(SZAKONYI, Z.; BALAZS, A.; MARTINEK, T. A.; FUELOEP*, F.; Tetrahedron: Asymmetry 17 (2006) 2, 199-204; Inst. Pharm. Chem., Univ. Szeged, H-6701 Szeged, Hung.; Eng.) -Klein 25-087

A systematic study of chiral homoprolinols and their derivatives in the catalysis of enantioselective addition of diethylzinc to aldehydes

“…It is interesting to note that the yield increased slightly (72%) in the case of 2h . Similar effect of N ‐substituent‐induced difference in enantioselectivity of other γ‐amino alcohol catalysts derived from α‐pinene has already been observed by Fülöp group 28. We also tested 2i in the reaction, the enantioselectivity decreased sharply giving the product with only 6% ee.…”

“…As an important approach to synthesize useful and optically active secondary alcohols, the asymmetric alkylation of carbonyl compounds with organozinc reagents has been of great interest 1, 2. Since the first report by Oguni to use ( S )‐leucinol as chiral ligand in the addition of diethylzinc to benzadehyde with moderate enantiomeric excess,3 and Noyori's work with (‐)‐3‐exo‐(dimethylamino)isoborneol (DAIB) as chiral ligand,4–9 tremendous efforts have been focused on exploring new amino alcohols as efficient catalysts and diverse ligand structures have been developed to date 10–68. Among them, β‐amino alcohols have been studied extensively and proven to be the best ligands 10–23.…”

“…Among them, β‐amino alcohols have been studied extensively and proven to be the best ligands 10–23. Comparatively, γ‐amino alcohols have been studied less than β‐amino alcohols even though satisfactory results were achieved with the former ligands 24–35…”

Stereoselective Syntheses and Application of Chiral Bi- and Tridentate Ligands Derived from (+)-Sabinol

“…In recent years, the discovery and application of new chiral auxiliaries and catalysts have become a crucial question in stereoselective syntheses [ 1 , 2 , 3 , 4 ]. To achieve new, efficient, and commercially available chiral catalysts, natural chiral terpenes [ 5 ], including (+)-pulegone [ 6 , 7 , 8 ], α- and β-pinene [ 9 , 10 , 11 , 12 , 13 , 14 ], and fenchone-camphor [ 15 , 16 , 17 , 18 , 19 ] have proved to be excellent sources. Starting from these readily available natural sources, several powerful chiral catalysts, including various di- and trifunctional synthons, such as 1,3-aminoalcohols and aminodiols, have been applied in stereoselective syntheses [ 5 , 20 ].…”

New 1,3-amino alcohols derived from enantiopure bridgehead β-aminobicyclo[2.2.2]oct-5-ene-2-carboxylic acids

“…Synthesis of enantiopure amino alcohols is of great importance in synthetic organic chemistry since they are a well established source of ligands for asymmetric synthesis (Blaser 1992;Ager et al 1996;Lait et al 2007) including enantioselective borane reduction of prochiral ketones (Corey et al 1987;Corey and Helal 1998;Deloux and Screbnik 1993;Li et al 1999;Krzemiński and Wojtczak 2005;Krzemiński and Zaidlewicz 2003;Hobuss et al 2008) or enantioselective addition of dialkylzinc (Kitamura et al 1986;Kossenjans and Martens 1998;Garcia Martinez et al 2002;Oliveira and Costa 2004;Szakonyi et al 2006;Binder et al 2009;Scarpi et al 2009;Wu et al 2009). Apart from this property, enantiopure amino alcohols are also important derivatives for the synthesis of various chemical compounds.…”