Lewis Acid‐Mediated Diastereoselective Reduction of <i>N</i>‐Protected β‐Amino Ketones: Influence of the Nature of the Metal Atom and of the Nitrogen Protecting Group

Bartoli, Giuseppe; Bartolacci, Massimo; Cortese, Manuela; Marcantoni, Enrico; Massaccesi, Massimo; Pela, Roberto; Sambri, Letizia

doi:10.1002/ejoc.200400016

Cited by 12 publications

(2 citation statements)

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“…On the basis of this, we have studied the reduction of N-protected α-alkyl-β-amino ketones 18 leading to the formation of syn-and anti-1-amino-3-hydroxy compounds (syn-19 and anti-19; Table 4). [52] An important conclusion to be drawn from the results in Table 4 is that the nature of the protecting group significantly influences the diastereoselectivity of the reduction of 18. [53] Although the number of examples is limited, it may be safely said that with these N-protected substrates the procedure for hydride addition is less diastereoselective than with the corresponding β-functionalised keto compound O-derivatives.…”

Section: Diastereoselective Reduction Of N-protected α-Alkyl-β-amino mentioning

confidence: 99%

Diastereoselective Lewis Acid Mediated Reductions of α‐Alkyl‐β‐Functionalized Carbonyl Compounds

et al. 2005

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A high stereochemical induction has often been observed in the reduction of ketones with stereogenic centres close to the carbonyl function. The level of stereoselectivity is particularly high when “hard” donor groups such as nitrogen or oxygen atoms are present in the molecule. These results have been commonly explained in terms of a chelate‐controlled process. However, this interpretation has recently been challenged, and in many cases an open‐chain mechanism can better account for the observed results. Thus, Lewis‐acid‐mediated chelation and nonchelation control is one of the most fundamental and practical concepts in transferring a nucleophile moiety to carbonyl compounds. In order to clarify the role of a hard Lewis acid in controlling the stereochemical outcome of a given reaction, the Lewis acid mediated reduction of a series of α‐alkyl‐β‐functionalized carbonyl compounds with metallic hydrides in various solvents was recently investigated. In particular, the results derived from the reductions in the presence of dry CeCl3 were compared to those obtained under the same experimental conditions but in the presence of TiCl4, whose ability to form chelation complexes is well established. These investigations show a stereochemical outcome that is fully consistent with a chelation‐controlled pathway in the case of titanium, and an open‐chain‐controlled pathway in the case of CeCl3. The strongly chelating TiCl4 led to the syn isomer in high diastereomeric excess in noncoordinating solvents at –78 °C with borane–Lewis base complex reducing agents, while nonchelating CeCl3 produced a high excess of the anti isomer in coordinating solvents at the same temperature with metal borohydrides as reducing agent. Therefore, our method based on the choice of CeCl3 or TiCl4 as a Lewis acid under the reported conditions represents a significant contribution to the development of new stereoselective reductions of α‐alkyl‐β‐functionalized ketones. These procedures are one of the best known ways to obtain an alcoholic moiety. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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Section: Diastereoselective Reduction Of N-protected α-Alkyl-β-amino mentioning

confidence: 99%

Diastereoselective Lewis Acid Mediated Reductions of α‐Alkyl‐β‐Functionalized Carbonyl Compounds

et al. 2005

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“…Undoubtedly the most straightforward route involves diastereoselective reduction of a b-amino ketone Mannich product by employing a suitable hydride donor. Besides several methods for the reduction of a-chiral b-amino ketones, [5][6][7] a number of reports on the stoichiometric reduction of b-branched b-amino ketones (with a methylene adjacent to the amine function) have been disclosed. [8][9][10][11] These include the diastereoselective reduction of N-sulfonyl-protected g-hydroxyimines, 12 synselective reductive amination of b-hydroxy ketones with p-anisidine and polymethylhydrosiloxane, 13 and dynamic kinetic resolution of N-Boc-protected g-amino ketones.…”

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Enantio- and diastereoselective synthesis of γ-amino alcohols

et al. 2015

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Anti‐Markovnikov Hydroamination of Racemic Allylic Alcohols to Access Chiral γ‐Amino Alcohols

Wang

Liu

et al. 2020

Angewandte Chemie

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A ruthenium-catalyzed formal anti-Markovnikov hydroamination of allylic alcohols for the synthesis of chiral g-amino alcohols is presented. Proceeding via an asymmetric hydrogen-borrowing process, the catalysis allows racemic secondary allylic alcohols to react with various amines, affording enantiomerically enriched chiral g-amino alcohols with broad substrate scope and excellent enantioselectivities (68 examples, up to > 99 % ee).

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Lewis Acid‐Mediated Diastereoselective Reduction of N‐Protected β‐Amino Ketones: Influence of the Nature of the Metal Atom and of the Nitrogen Protecting Group

Cited by 12 publications

References 83 publications

Diastereoselective Lewis Acid Mediated Reductions of α‐Alkyl‐β‐Functionalized Carbonyl Compounds

Diastereoselective Lewis Acid Mediated Reductions of α‐Alkyl‐β‐Functionalized Carbonyl Compounds

Enantio- and diastereoselective synthesis of γ-amino alcohols

Anti‐Markovnikov Hydroamination of Racemic Allylic Alcohols to Access Chiral γ‐Amino Alcohols

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