Hydroboration–oxidation reaction

In organic chemistry, the hydroboration–oxidation reaction is a two-step organic reaction that converts an alkene into a neutral alcohol by the net addition of water across the double bond. The hydrogen and hydroxyl group are added in a syn addition leading to cis stereochemistry. Hydroboration–oxidation is an anti-Markovnikov reaction, with the hydroxyl group attaching to the less-substituted carbon.

Quotes

• The hydration of alkenes via hydroboration-oxidation … provides a valuable tool for the synthesis of a wide variety of alcohols of predictable regio- and stereochemistry. … The mono- and dialkylboranes are themselves useful hydroborating agents for sterically less hindered alkenes.
  • George S. Zweifel and Michael H. Nantz, Modern Organic Synthesis (2006), Ch. 5 : Functional Group Transformations: The Chemistry of Carbon-Carbon π-Bonds and Related Reactions.

• An important feature of the hydroboration reaction is the regioselectivity observed with unsymmetrical alkenes. Generally, boron attacks positions of highest electron density and lowest steric congestion. This working hypothesis rationalizes the regioselectivity and stereo- selectivity of most hydroboration reactions.
  • George S. Zweifel and Michael H. Nantz, Modern Organic Synthesis (2006), Ch. 5 : Functional Group Transformations: The Chemistry of Carbon-Carbon π-Bonds and Related Reactions.

• The rates of hydroboration of alkenes with dialkylboranes vary over a wide range.
  • George S. Zweifel and Michael H. Nantz, Modern Organic Synthesis (2006), Ch. 5 : Functional Group Transformations: The Chemistry of Carbon-Carbon π-Bonds and Related Reactions.

• The four-center transition state for hydroboration of alkenes discussed above implies that addition of the B-H bond to a double bond proceeds in a syn-manner.
  • George S. Zweifel and Michael H. Nantz, Modern Organic Synthesis (2006), Ch. 5 : Functional Group Transformations: The Chemistry of Carbon-Carbon π-Bonds and Related Reactions.

• The facile reactions of olefins and dienes with various hydroborating agents makes a variety of organoboranes readily available. Organoboranes tolerate many functional groups and are formed in a stereospecific manner. The boron atom in these organoboranes can be readily substituted with a variety of functional groups.
  • George S. Zweifel and Michael H. Nantz, Modern Organic Synthesis (2006), Ch. 5 : Functional Group Transformations: The Chemistry of Carbon-Carbon π-Bonds and Related Reactions.