Hydroboration

Survey

Through the implementation of a terminal alkene with borane the alkylborane 1 is formed by addition. By addition of another molecule of the alkene that is produced dialkylborane 2:

By addition of a third molecule of the alkene the trialkylborane 3 arises:

The alkylboranes 1,2,3 can be reacted with hydrogen peroxide and sodium hydroxide to give primary alcohols followed by:

How many molecules of the primary alcohol can be synthesized from one molecule of the borane, depends on the number of alkyl groups of the borane.

Reaction mechanism

A proposal for the reaction mechanism:

The alkene 1 is implemented by adding the borane 2 to the more highly substituted borane 3. By triple treatment with Hydroperoxidanionen and subsequent elimination of the alkyl groups of each of a hydroxide ion borane 3 are converted into alcoholate. R1 is a hydrogen atom, the hydride instead be converted into analog hydroxyl groups. Thus, the Boran created 4 The resulting borane 4 is then cleaved by addition of hydroxide ions in an alcoholate and the borane 5. The alcoholate is protonated by the borane 5 and the result is the primary alcohol 7 Moreover, the ion is formed 6 If it is in the OR1 groups of 6 to alcoholate ion, this can be cleaved also by the addition of hydroxide ions, and protonation to alcohols be transferred.