Synthesis of chiral non-racemic 1,2-diamines from O-acetyl mandelic acid: application in enantioselective deprotonation of epoxides and diethylzinc addition to aldehydes

Studies Toward the Synthesis of Spirolides: Assembly of the Elaborated E-Ring Fragment

“…According to this method, chiral Koga-type bases or other chiral lithium amides are used with stereodefined acyclic alpha-branched esters to achieve highly stereoselective enolizations. As a part of an ongoing investigation to improve stereoselectivity and to define the scope and utility of this technique, we explored new bases, including the lithium amides formed from benzylamines ( S )- 7 11 and ( R )- 7 12. Using ester 5 , we compared the stereoselectivity of the enolization to that obtained with lithium amides ( S )- 6 -Li and ( R )- 6 -Li produced from trifluoroethylamines ( S )- 6 and ( R )- 6 , which showed the highest stereocontrol previously 10.…”

Evaluation of the use of mandelate derivatives to determine the enantiomeric purity and the absolute configuration of secondary cyclohexenols

“…6 N,N′-dicyclohexylcarbodiimide (DCC) and catalytic 4-(dimethylamino)pyridine (DMAP) in dichloromethane (DCM) gave a mixture of diastereomeric O-acetylmandelates 5 in 70% yield (Scheme 2). 7 Integration of the 1 H NMR spectrum indicated that the 73:27 endo/exo and 50:50 R/S ratios were maintained.…”

Enantioselective ethylation of aldehydes with 1,3-N-donor ligands derived from (+)-camphoric acid

“…Diamine ligands and derivatives have received less attention, although there are various examples of good ees obtained with this type of ligands. [4][5][6][7][8][9] A considerable amount of work has been reported in the literature on the use of 1,2-bidentate ligands, while 1,3-and 1,4-bidentate ligands have been less used and studied. [10][11][12] In contrast to 1,2-ligands, which form a five-membered chelate with the zinc atom in the transition state, 1,3-and 1,4-ligands form conformationally flexible six-or seven-membered catalytic chelates with the Zn atom.…”

“…Although a great number of N,N 0 -disulfonated and diacylated chiral amines have been tested in the enantioselective alkylation with diethylzinc, especially in the presence of Ti(O i Pr) 4 , [17][18][19][20] there are fewer reports in the literature on the use of monosulfonated or monoacylated amines. 1,7,21,22 Urabe et al 23 reported the use of a dialkylated diamine, a diamide and some dialkylaminoamides derived from (+)-camphoric acid in the reaction of benzaldehyde with several organometallic reagents, including diethylzinc.…”