- Highly stereoselective syntheses of proline-derived vicinal amino alcohols through grignard addition onto N-tosylprolinal
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A highly diastereoselective Grignard addition to N-tosyl-l-prolinal has been developed to deliver a variety of proline-derived vicinal amino alcohols in good to excellent yields with high diastereoselectivities. A similar selectivity was also obtained by using N-tosyl-d-prolinal. The methodology has been applied to the synthesis of medicinally important 3-hydroxy-2-phenylpiperidines.
- Chaudhuri, Saikat,Parida, Amarchand,Ghosh, Santanu,Bisai, Alakesh
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p. 215 - 220
(2016/01/20)
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- Enantioselective bromolactonization using an S-alkyl thiocarbamate catalyst
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The apple never falls far from the tree: S-alkyl thiocarbamate 1 (see scheme, NBP=N-bromophthalimide) was prepared in high yield through a synthetic sequence involving a Newman-Kwart rearrangement of the corresponding O-alkyl thiocarbamates. Compound 1 was used to catalyze bromolactonization, thus providing enantioenriched δ-lactones in excellent yield and enantioselectivity. Copyright
- Jiang, Xiaojian,Tan, Chong Kiat,Zhou, Ling,Yeung, Ying-Yeung
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p. 7771 - 7775
(2012/09/07)
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- N-Tritylprolinal: An Efficient Building Block for the Stereoselective Synthesis of Proline-Derived Amino Alcohols
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N-Tritylprolinal (prepared in four steps from L-proline) shows a very high Felkin diastereoselectivity in its reaction with various nucleophiles, leading to a straightforward and highly stereoselective access to syn-proline-derived amino alcohols.
- Bejjani, Joseph,Chemla, Fabrice,Audouin, Max
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p. 9747 - 9752
(2007/10/03)
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- Alkylation of 2-Lithio-N-Methylpiperidines and -pyrrolidines: Scope, Limitations, and Stereochemistry
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The scope and limitations of the alkylation of racemic and nonracemic 2-lithipiperidines and -pyrrolidines, obtained by transmetalation of the corresponding stannanes, is reported.These organolithiums react with a variety of electrophiles to afford 2-substituted pyrrolidines and piperidines in excellent yield.With primary alkyl halides the reaction proceeds with net inversion of configuration at the metal-bearing carbon in the piperidines; in the pyrrolidines there is a mixture of inversion and retention, with the former predominating.With most carbonyl electrophiles (carbon dioxide, dimethyl carbonate, methyl chloroformate, pivaloyl chloride, benzaldehyde, and dialkyl ketones), retention is observed in both cases.Electrophiles such as benzophenone, benzyl bromide, and tert-butyl bromoacetate afford racemic coupling products.A mechanistic interpretation is presented.
- Gawley, Robert E.,Zhang, Qianhui
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p. 5763 - 5769
(2007/10/03)
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- Catalytic Asymmetric Induction. Highly Enantioselective Addition of Dialkylzincs to Aldehydes Using Chiral Pyrrolidinylmethanols and Their Metal Salts
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A series of chiral pyrrolidinylmethanols were synthesized from (S)-proline.Optically active secondary alcohols (R and S enantiomers, respectively) in up to 100percent enantiomeric excess (ee) were obtained in high yields from the enantioselective addition of dialkylzincs to aldehydes catalyzed by 2-5 mol percent of chiral pyrrolidinylmethanols.The sense of the asymmetric induction and the degrees of enantioselectivities were highly dependent on the structure of the catalysts. (+)-DPMPM (3, tertiary amino tertiary alcohol) catalyzed the reaction of aryl, α,β-unsaturated, and aliphatic aldehydes to afford (S) alcohols in high ee's.When the lithium salt of 3 was employed as catalyst in the reactions of aryl and α,β-unsaturated aldehydes, the ee's of (S) alcohols reached 100percent.On the other hand, (-)-erythro-PNPM (10, tertiary amino secondary alcohol) afforded (R) alcohols in high ee (100percent ee).The steric course of the reaction is discussed.
- Soai, Kenso,Ookawa, Atsuhiro,Kaba, Tatsuya,Ogawa, Kazuo
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p. 7111 - 7115
(2007/10/02)
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- Complementary Catalytic Asymmetric Induction in the Enantioselective Addition of Diethylzinc to Aldehydes
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Both enantiomers of sec-alcohols were obtained in high enantiomeric excess (up to 92 percent) from the enantioselective addition of diethylzinc to aldehydes using chiral pyrrolidinylmethanol derivatives as catalysts.
- Soai, Kenso,Ookawa, Atsuhiro,Ogawa, Kazuo,Kaba, Tatsuya
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p. 467 - 468
(2007/10/02)
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