Open-flask, Non-dissociative Hydroboration Using Ammonia Borane

Michael P Drolet, Purdue University

Abstract

The open-flask, non-dissociative hydroboration of alkenes and alkynes with air- and moisture-stable ammonia borane is herein detailed. Terminal alkenes react with ammonia borane in refluxing tetrahydrofuran to give trialkylborane-ammonia complexes, which degrade upon isolation, but may be readily oxidized to their corresponding alcohols in excellent yields. Two equivalents of internal alkenes undergo hydroboration followed by dehydrogenation to give aminodialkylboranes in near quantitative yields and excellent purity. These aminodialkylboranes can also be oxidized to their corresponding alcohols in good yields. During these reactions, the Lewis base ammonia does not dissociate from the boron center, as indicated by its retention in the organoborane product. This methodology may also be extended to aryl alkynes which, with excess ammonia borane, provides 1,2-dihydroboration to 1,2-diboro- derivatives. These can be oxidized to 1,2-diols in very good yields. Finally, progress has been made in the activation of ammonia borane with iodomethane to promote hydroboration at ambient temperature while maintaining air and moisture tolerant conditions.

Degree

Ph.D.

Advisors

Ramachandran, Purdue University.

Subject Area

Chemistry

COinS