Diastereoselective Addition of Organometallics to <i>N</i>-(α-Ketoacyl)-<i>trans</i>-2,5-bis(methoxymethoxymethyl)pyrrolidine

Kawanami, Yasuhiro; Fujita, Izumi; Ogawa, Shiho; Katsuki, Tsutomu

doi:10.1246/cl.1989.2063

Cited by 13 publications

(1 citation statement)

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“…In the reaction of substrates 3d-f having a bulky 2'-substituent, the steric hindrance imposed by the C(2')-* In some reports, chelationcontrolled Grignard additions to chiral ketones gave higher selectivities in THF than those in diethyl ether; see ref. 4 and references cited therein, and ref. 5.…”

Section: Mechanistic Considerations With Regard To the Asymmetricmentioning

confidence: 99%

Investigation of the diastereoselectivity in the addition of organometallics to the α-keto esters of axially chiral 1,1′-binaphthalen-2-ol derivatives

Tamai¹,

Nakano²,

Miyano³

1994

J. Chem. Soc., Perkin Trans. 1

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The inherent chiral induction abilities of axially chiral 2'-substituted 1 ,I '-binaphthalen-2-ols 2a-f as the chiral auxiliary for the addition of organometallics to their a-keto acid esters were examined as a function of the following reaction variables: size of the 2'-substituent, nature of the organometallic reagent, solvent, and temperature. In the addition of M e M g l to the phenylglyoxylates 3a-f of the alcohols 2a-f, the corresponding atrolactic acid esters 5a-f and 6a-f were obtained with up t o 52% diastereoisomeric excess (d.e.). The preferred diastereoisomer depended on the size of the 2'substituent, and thus could not solely be determined b y the helicity of the 1.1'-binaphthalene framework. B y using MeZnl as the nucleophile, the selectivity increased up to 84% d.e. with the same diastereofacial selectivity as that of MeMgl. O n the other hand, the diastereofacial selection was reversed when MeTiCI, was employed as the nucleophile, with low selectivity (1 4% d.e.).It is concluded that M e M g l or MeZnI, as a nucleophile of low Lewis acidity, adds to the keto ester moiety in the s-trans conformation, while the strong Lewis acid MeTiCI, mainly adds t o the s-cis conformer from the same direction as that of the Grignard addition, thus giving the opposite diastereoisomer.

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Section: Mechanistic Considerations With Regard To the Asymmetricmentioning

confidence: 99%