Ruthenium and Borane catalyzed hydroboration reactions

Abstract

In the first chapter, an efficient and simple catalytic method for the selective and partial reduction of aldazines using ruthenium catalyst [Ru(p-cymene)Cl2]2 has been accomplished. Under mild conditions, aldazines undergo the addition of pinacolborane in the presence of a ruthenium catalyst, which delivered N-boryl-Nbenzyl hydrazone products. Notably, the reaction is highly selective and results in exclusive mono-hydroboration and desymmetrization of symmetrical aldazines. Mechanistic studies indicate the involvement of in situ formed intermediate [{(η6-p-cymene)RuCl}2(μ-H-μ-Cl)] in this selective hydroboration. In the second chapter, organoborane catalyzed hydroboration of nitriles provides N,N-diboryl amines, which act as an efficient synthon for the synthesis of assortments of primary amines and secondary amides. Known nitrile hydroboration methods are dominated by metal catalysis. A simple and effective method for metal-free hydroboration of nitriles using commercially available diborane [H-B-9-BBN]2 as a catalyst and pinacolborane as a turnover reagent is reported. The reaction of monomeric H-B-9-BBN with nitriles leads to the hydrido-bridged diborylimine intermediate, and the subsequent sequential double hydroboration-transborylation pathway involving B-N/B-H σ bond metathesis is proposed.