Uses of Organoboranes and Organoborates in Organic Synthesis

Certain hydroboration reactions which are slow under normal conditions due to their heterogeneous nature proceed much faster under the effects of ultrasound. Several acyclic and cyclic trienes have been hydroborated with borane or triethylamineborane in THF and the stereochemistry of the products investigated. A systematic study of the hydroboration of representative heterocyclic olefins with four different reagents has been undertaken in order to establish optimum conditions for the reactions. This study has been followed by an investigation into the relative rates of reaction of 9-BBN with oxygen and sulphur containing heterocyclic olefins.  

The action of four hydroborating reagents on 1,4-epoxy-l,4--dihydronaphthalene has been compared. Depending on the steric 

There continues to be considerable effort applied to the use of organoboranes in chiral synthesis. A convenient procedure for the synthesis of various 6-chiral boronic esters of essentially 100% ee which are not available by direct asymmetric hydroboration methods has been developed and their synthetic utility described. 

A method for upgrading the enantiomeric purities of (+)-longifolene and (+)-3-carene to levels approaching 100% ee has been reported. This means that the corresponding dialkyIboranes are now available for asymmetric hydroboration reactions. 

Zinc modified cyanoborohydride has been found to be a selective and versatile reducing agent and the reaction of potassium hydride with 9-BBN borinic esters gives rise to a new class of stereoselective reducing agents.  

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