Hydroboration. 97. Synthesis of New Exceptional Chloroborane-Lewis Base Adducts for Hydroboration. Dioxane-Monochloroborane as a Superior Reagent for the Selective Hydroboration of Terminal Alkenes
Josyula V. B. Kanth and Herbert C. Brown*
*H. C. Brown Center for Borane Research, Department of Chemistry, Purdue
University, West Lafayette, Indiana 47907, Email: hcbrown
purdue.edu
J. V. B. Kanth, H. C. Brown, J. Org. Chem, 2001, 66, 5359-5365.
DOI: 10.1021/jo015527o
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Abstract
Convenient methods for the preparation of stable and non-volatile mono- and dichloroborane adducts of dioxane from dioxane-BCl3 and NaBH4 in the presence of catalytic amounts of tri- or tetraglyme were developed. The dioxane-monochloroborane adduct hydroborates representative olefins cleanly and rapidly and lead to the corresponding alcohols in quantitative yields after oxidation.
preparation of borane reagents
Details
The document discusses the synthesis and application of new chloroborane-Lewis base adducts for hydroboration, focusing on dioxane-monochloroborane as a superior reagent for the selective hydroboration of terminal alkenes. Various oxygen-containing Lewis bases were tested, with dioxane forming the most stable and reactive adducts. Dioxane-monochloroborane hydroborates olefins cleanly and rapidly, yielding primary alcohols with high regioselectivity (>99.5%) after oxidation. The study also highlights the exceptional selectivity of dioxane-dichloroborane towards 2-substituted terminal olefins. The document details the preparation methods for these adducts and their hydroboration reactions, demonstrating their advantages over traditional borane reagents like BH3:THF and BMS. The findings suggest that dioxane-monochloroborane is a preferred reagent for hydroboration due to its stability, reactivity, and high regioselectivity, making it valuable for organic synthesis, including the production of various functional groups and natural products. The study also explores the potential of other chloroborane adducts, such as those with monoglyme and β-chloroethyl ether, for hydroboration, although they require specific conditions for optimal performance.
Key Words
Hydroboration, Alcohols, Hydrogen Peroxide
ID: J42-Y2001-320
