Selective reductions. 37. Asymmetric reduction of prochiral ketones with B-(3-pinanyl)-9-borabicyclo[3.3.1]nonane

Brown, Herbert C.; Pai, Ganesh G.

doi:10.1021/jo00209a008

Cited by 124 publications

(30 citation statements)

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“…5,6 Furthermore, Brown et al found that the exclusion of solvent from the reduction of ketones provided similar gains in selectivity. 7 These observations are consistent with the putative side reaction, given that the volume of activation for dehydroboration ( TS3 ) is likely to be large and positive and the relative entropy of solvation for the two dissociation products is likely to be higher than that for the single progenitor species.…”

supporting

confidence: 72%

Computational and experimental structure–reactivity relationships: evidence for a side reaction in Alpine-Borane reductions of d-benzaldehydes

Zhu

Reyes

Meyer

2009

Tetrahedron Letters

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Extraordinary stereoselectivity, approaching 100%, has been reported in the reductions of d-benzaldehydes by B-isopinocampheyl-9-borabicyclo[3.3.1]nonane (Alpine-Borane). This is likely because of the extreme size disparity of groups on either side of the carbonyl. Here, we present a structure–reactivity study whereby the reductions of variably substituted d-benzaldehydes are explored using highly sensitive measures for enantiomeric excess and relative reactivity. These results are compared to the relative rates predicted from density functional calculations. The results indicate that 2,6–disubstitution adversely affects the stereoselectivity by means of a non-selective reduction via the dehydroboration product of Alpine-Borane, 9-borabicyclo[3.3.1]nonane.

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supporting

confidence: 72%

Computational and experimental structure–reactivity relationships: evidence for a side reaction in Alpine-Borane reductions of d-benzaldehydes

Zhu

Reyes

Meyer

2009

Tetrahedron Letters

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“…(R)-and (S)-ethyl 2-hydroxy-2-(9-anthryl)acetate (5) were obtained by asymmetric reduction of ethyl (9-anthryl)-glyoxylate with (R)-and (S)-ALPINE BORANE, respectively, (prepared in situ from 9-BBN and (+)-and (-)-pinene by the usual procedure). 24 It was methylated to measure the ee by HPLC (Chiral column) and then hydrolyzed to compare the stereochemistry with that of 9-AMA. The absolute stereochemistry was confirmed by CD.…”

Section: Methodsmentioning

confidence: 99%

Assignment of the Absolute Configuration of α-Chiral Carboxylic Acids by ¹H NMR Spectroscopy

et al. 2000

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The prediction of the absolute configuration of alpha-chiral carboxylic acids from the 1H NMR spectra of their esters with (R)- and (S)-ethyl 2-hydroxy-2-(9-anthryl) acetate [(R)- and (S)-9-AHA, 5] is discussed. Low-temperature NMR experiments, MM, semiempirical, and aromatic shielding effect calculations allowed the identification of the main conformers and showed that, in all esters studied, conformer ap is the most stable. A simple model for the assignment of the absolute configuration from NMR data is presented, and its reliability is corroborated with acids 6-31 of known absolute configuration. In addition to 5, other auxiliary reagents with open (32-38) and cyclic (39-42) structures have also been studied. trans-(+)- and (-)-2-phenyl-1-cyclohexanol (41) was found to be particularly efficient and produced delta delta RS values similar to those of 5.

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“…The asymmetric reduction of α-haloketones is potentially a useful process to obtain halohydrins, which are valuable syn-thetic intermediates for the preparation of a wide range of com-pounds of biological interests [ 679 , 680 , 681 , 682 , 683 , 684 , 685 , 686 , 687 , 688 , 689 , 690 , 691 , 692 , 693 , 694 , 695 ]. The reaction of α-halo-ketones with sodium borohydride is one of the most popular reduction processes and results in reduction of the carbonyl function with formation of the corresponding halohydrins 331 ( Scheme 98 ) [ 696 , 697 , 698 , 699 , 700 , 701 ].…”

Section: Miscellaneous Reactions Of α-Haloketonesmentioning

confidence: 99%

The Chemistry of α-Haloketones and Their Utility in Heterocyclic Synthesis

2003

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Selective reductions. 37. Asymmetric reduction of prochiral ketones with B-(3-pinanyl)-9-borabicyclo[3.3.1]nonane

Cited by 124 publications

References 4 publications

Computational and experimental structure–reactivity relationships: evidence for a side reaction in Alpine-Borane reductions of d-benzaldehydes

Computational and experimental structure–reactivity relationships: evidence for a side reaction in Alpine-Borane reductions of d-benzaldehydes

Assignment of the Absolute Configuration of α-Chiral Carboxylic Acids by ¹H NMR Spectroscopy

The Chemistry of α-Haloketones and Their Utility in Heterocyclic Synthesis

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Selective reductions. 37. Asymmetric reduction of prochiral ketones with B-(3-pinanyl)-9-borabicyclo[3.3.1]nonane

Cited by 124 publications

References 4 publications

Computational and experimental structure–reactivity relationships: evidence for a side reaction in Alpine-Borane reductions of d-benzaldehydes

Computational and experimental structure–reactivity relationships: evidence for a side reaction in Alpine-Borane reductions of d-benzaldehydes

Assignment of the Absolute Configuration of α-Chiral Carboxylic Acids by 1H NMR Spectroscopy

The Chemistry of α-Haloketones and Their Utility in Heterocyclic Synthesis

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Assignment of the Absolute Configuration of α-Chiral Carboxylic Acids by ¹H NMR Spectroscopy