1987
DOI: 10.1002/hlca.19870700719
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MNDO Analysis of Regio‐ and Stereoselectivity in Hydroboration

Abstract: The origin of regioselectivity in hydroboration of olefins has been analyzed by MNDO methodology. With a standard transition structure derived from full MNDO optimizations, a linear correlation between calculated and experimental regioselectivities has been found. A similar approach applied to asymmetric inductions of hydroboration with chiral hydroborating agents lead also to an acceptable linear correlation between calculated and experimental results. The MNDO method has been used for a search of alternative… Show more

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Cited by 15 publications
(4 citation statements)
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“…These results indicate that the effectiveness of these two complimentary reagents depends on their steric requirements. This is also supported by literature reports, based on theoretical calculations, suggesting that the steric bulk and environment around the boron atom in the pinene-based borane reagents are critical for achieving a high degree of stereoselection in asymmetric hydroboration. This has been very well illustrated by the application of the sterically bulkier chiral auxiliaries, readily derived from easily accessible α-pinene, namely 2-ethyl-, 2- n -propyl-, and 2-isopropylapopinenes in asymmetric reduction and hydroboration reactions.…”
supporting
confidence: 86%
“…These results indicate that the effectiveness of these two complimentary reagents depends on their steric requirements. This is also supported by literature reports, based on theoretical calculations, suggesting that the steric bulk and environment around the boron atom in the pinene-based borane reagents are critical for achieving a high degree of stereoselection in asymmetric hydroboration. This has been very well illustrated by the application of the sterically bulkier chiral auxiliaries, readily derived from easily accessible α-pinene, namely 2-ethyl-, 2- n -propyl-, and 2-isopropylapopinenes in asymmetric reduction and hydroboration reactions.…”
supporting
confidence: 86%
“…This unsatisfactory result led us to examine modification of the IpcBH 2 reagent in the hope of achieving improved optical yields. Literature reports suggest that the steric and electronic environment around the boron atom in pinene-based reagents must be critical for achieving a high degree of stereoselection in asymmetric hydroboration. Accordingly, we decided to explore the effect of introducing a chlorine atom into the IpcBH 2 reagent.…”
Section: Resultsmentioning
confidence: 99%
“…Over the years the accumulated results have persuaded us that the remarkable chiral effectiveness of the Ipc 2 B- structure must have its origin in the 2-methyl group of the rigid “Ipc” structure 3d. Moreover, the substituent on the boron atom of the reagent also plays an important role. 5b, As a result, we decided to undertake the synthesis of a representative number of 2-R-apopinene structures, by replacing the 2-methyl of α-pinene ( 1a , Ipc) by larger R groups, providing 2-ethyl- ( 1b , Eap), 2- n -propyl- ( 1c , Pr), 2-isobutyl- ( 1d , i -Bu), 2-phenyl- ( 1e , Pap), and 2-isopropyl- ( 1f , i -Pr) 13 apopinenes in the hope of optimizing the steric fit between the substrate and that of the reagent in their reactions. We also decided to examine the effect of varying the halogen in the corresponding BX 2 derivatives.…”
Section: Introductionmentioning
confidence: 99%