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Chiral imine acetal with lithium enolate

Asymmetric Mannich-type reactions provide useful routes for the synthesis of enantiomerically enriched P-amino ketones or esters [48a, 48b]. For the most part, these methods involve the use of chirally modified enolates or imines. Only a handful of examples has been reported on the reaction of imines with enolates of carboxylic acid derivatives or silyl ketene acetals in the presence of a stoichiometric amount of a chiral controller [49a, 49b, 49c]. Reports describing the use of a substoichiometric amount of the chiral agent are even more scarce. This section contains some of the most recent advances in the field of catalytic enantioselective additions of lithium enolates and silyl enol ethers of esters and ketones to imines. [Pg.904]

Hydroxy-4-phenyl-P-lactams. The lithium enolate of (silyloxy)acetates (2) couple with the N-(trimethylsilyl)imine 3 to give 3-hydroxy-4-aryl- -lactams (4). The stereoselectivity depends in part on the size of the silyloxy group but mainly on the ester group. Use of either (+)- or (—)-/ra/w-2-phenyl-l-cyclohexyl (I) as the chiral auxiliary results entirely in a cw-/3-lactam (4) in 80% yield and 96-98% ee. Use of (-)-menthyl or of Oppolzer s D-isobornyl auxiliary (12,103-104) results in lower yields and enantioselectivity. The cyclocondensation with the ester 2 from (-)-l results in (3R,4S)-4 in 96% ee. On desilylation and acid hydrolysis, this lactam provides (2R,3S)-... [Pg.275]


See other pages where Chiral imine acetal with lithium enolate is mentioned: [Pg.766]    [Pg.791]    [Pg.344]    [Pg.933]    [Pg.933]    [Pg.933]   
See also in sourсe #XX -- [ Pg.14 , Pg.497 , Pg.498 ]

See also in sourсe #XX -- [ Pg.14 , Pg.497 , Pg.498 ]




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Acetals chiral

Acetate enolates

Acetate enolates chiral

Chiral acetate

Chiral enolate

Chiral imine

Chiral imine acetal

Chiral lithium enolates

Enol acetals

Enol acetates

Enol imines

Enol-imine

Enolate lithium

Enolates chiral

Enolates lithium

Imine enolates

Imine enolates, chiral

Imines acetals

Imines chiral

Imines enolates

Lithium imines

With imines

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