Highly Stereoselective Syntheses of Proline-Derived Vicinal Amino Alcohols through Grignard Addition onto N-Tosylprolinal
摘要:
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.
Both enantiomers of sec-alcohols were obtained in high enantiomeric excess (up to 92%) from the enantioselectiveaddition of diethylzinc to aldehydes using chiral pyrrolidinylmethanol derivatives as catalysts.
The apple never falls far from the tree: S‐alkylthiocarbamate 1 (see scheme, NBP=N‐bromophthalimide) was prepared in high yield through a synthetic sequence involving a Newman–Kwart rearrangement of the corresponding O‐alkylthiocarbamates. Compound 1 was used to catalyze bromolactonization, thus providing enantioenriched δ‐lactones in excellent yield and enantioselectivity.
Alkylation of 2-lithio-N-methylpiperidines and -pyrrolidines: scope, limitations, and stereochemistry
作者:Robert E. Gawley、Qianhui Zhang
DOI:10.1021/jo00123a008
日期:1995.9
The scope and limitations of the alkylation of racemic and nonracemic 2-lithiopiperidines 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.
<i>N</i>-Tritylprolinal: An Efficient Building Block for the Stereoselective Synthesis of Proline-Derived Amino Alcohols
作者:Joseph Bejjani、Fabrice Chemla、Max Audouin
DOI:10.1021/jo034976g
日期:2003.12.1
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.
SOAI KENSO; OOKAWA ATSUHIRO; OGAWA KAZUO; KABA TATSUYA, J. CHEM. SOC. CHEM. COMMUN.,(1987) N 6, 467-468