Ketones organoborane synthesis

The syntheses of carbon-13 labelled trans-tricyclic ketones 93 and 94 have been carried out79 via the cyanidation reaction of organoborane (equation 43). The isomerically pure tram -tricyclic ketones 93 and 94 were needed in connection with the undertaken synthesis... 

Organoboranes are used for ketone synthesis under basic conditions. The cyclic ketone 482 is prepared from alkenyl iodode 479. Hydroboration of terminal double bond, followed by carbonylation generates 480, and the cyclic ketone 482 is formed by intramolecular transmetallation of 480 to afford 481 [236],... 

Synthesis of pure enantiomers. Brown and Singaram1 have reviewed the chiral organoboranes obtained from (+)- and (- )-pinene and their use for synthesis of optically pure amines, halides, hydrocarbons, lithium alkylborohydrides, ketones, aldehydes, a-chiral acids, esters, nitriles, alkynes, and alkenes. 

The reaction of organoboranes with catechol dichloromethylene ether in the presence of methyllithium provides a synthesis of symmetrical ketones (Eq. 34) From the result of a crossover experiment by using a mixture of two different trialkylboranes, the reaction was confirmed to proceed through intramolecular reaction pathways. 

The anions 1 are particularly useful for synthesis of hindered ketones. Thus they react with even hindered trialkylboranes to form organoboranes, which are converted into ketones by alkaline hydrogen peroxide. A typical procedure is formulated. 

Selective Hydroboration and Synthetic Utility of Organoboranes Thus Obtained TaMe 3. Synthesis of Unsymmetrical Ketones via Thexyldialkylboranes... 

Brown, H. C., Srebnik, M., Ramachandran, P. V. Chiral synthesis via organoboranes. 22. Selective reductions. 44. The effect of the steric requirements of the alkyl substituent in isopinocampheylalkylchloroboranes for the asymmetric reduction of representative ketones. J. Org. Chem. 1989,54, 1577-1583. 

The protonolysis of alkenyldialkylboranes to give -alkenes can be conducted, in most cases, under neutral conditions using methanol. More hindered alkenyldisiamylboranes react less well, unless a small amount of a carboxylic acid is added. A variety of Z-alkenyl pheromones was prepared using this method. The synthesis of trans-alkenes and unsymmetrical ketones was also accomplished using vinylic organoborane chemistry.7... 

A useful transformation in synthesis is the reaction of an organoborane to form a carbon-carbon bond. One method to achieve this is by addition of carbon monoxide, followed by oxidation, which can be directed to give primary, secondary or tertiary alcohols, aldehydes or ketones under appropriate conditions. On heating, many... 

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