Ch_322a_11.08

Ch_322a_11.08 - more favored C C CH 3 H H H H BH 2 major product Note The syn stereochemistry of hydroboration necessarily follows from the

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The Mechanism of Hydroboration The electron-deficient borane (Lewis acid) is believed to form a ! -complex with the ! -bond of the alkene. C=C + B CH 3 H H H H H H C=C CH 3 H H H B H H H ! + ! - " -complex fast fast
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The ! -complex reacts by way of a four-center transition state that determines the regiochemistry of the addition reaction. The two competing modes of reaction are shown below. C=C CH 3 H H H B H H H ! + ! - C C CH 3 H H H B-H H H C C CH 3 H H H ! + ! - H-B H H ! + ! - sterically and electronically less favored sterically and electronically
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Unformatted text preview: more favored C C CH 3 H H H H BH 2 major product Note: The syn stereochemistry of hydroboration necessarily follows from the four-center transition state. Quiz 11.08 Provide the products of the following hydroboration reactions. C=CH 2 CH 3 CH 3 BH 3 .THF THF CH 3 BH 3 .THF THF What term describes the stereochemistry of the hydroboration reaction? CH 3 CHCH 2 BH 2 CH 3 CH 3 H H BH 2 syn addition...
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This note was uploaded on 07/22/2009 for the course CHEM 322AL taught by Professor Jung during the Summer '07 term at USC.

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Ch_322a_11.08 - more favored C C CH 3 H H H H BH 2 major product Note The syn stereochemistry of hydroboration necessarily follows from the

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