Room-Temperature Rhodium-Catalyzed Regioselective B(4)-H Hydroxylation of Pyridyl-o-carboranes Using Koser's Reagent

Area of Science:

• Organometallic Chemistry
• Carborane Chemistry
• Synthetic Organic Chemistry

Background:

• Ortho-carboranes are versatile boron-containing compounds with unique electronic and steric properties.
• Functionalization of carboranes, particularly at the boron cage, is crucial for expanding their applications.
• Regioselective B-H functionalization remains a synthetic challenge in carborane chemistry.

Purpose of the Study:

• To establish a novel method for the regioselective hydroxylation of pyridyl-ortho-carboranes.
• To develop an efficient synthetic route to B(4)-hydroxylated ortho-carborane derivatives.

Main Methods:

• Rhodium-catalyzed reaction utilizing Koser's reagent.
• Direct B(4)-H hydroxylation of 1-pyridyl-ortho-carboranes.
• Room temperature reaction conditions.

Main Results:

• Successful regioselective B(4)-H hydroxylation of pyridyl-ortho-carboranes was achieved.
• Moderate to high isolated yields of B(4)-hydroxylated ortho-carborane derivatives were obtained.
• The method demonstrated tolerance towards various alkyl-, aryl-, and substituted pyridyl-containing substrates.

Conclusions:

• A new, efficient method for synthesizing B(4)-hydroxylated ortho-carboranes has been developed.
• The reaction proceeds under mild conditions and offers broad substrate scope.
• Mechanistic studies suggest Koser's reagent is the source of the hydroxyl group.