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Efficient Organocatalytic Dehydrogenation of Ammonia Borane.

ABSTRACT: Dehydrogenation of ammonia borane by sterically encumbered pyridones as organocatalysts is reported. With 6-tert-butyl-2-thiopyridone as the catalyst, a turnover frequency (TOF) of 88?h^-1 was achieved. Experimental mechanistic investigations, substantiated by DLPNO-CCSD(T) computations, indicate a mechanistic scenario that commences with the protonation of a B-H bond by the mercaptopyridine form of the catalyst. The reactive intermediate formed by this initial protonation was observed by NMR spectroscopy and the molecular structure of a surrogate determined by SCXRD. An intramolecular proton transfer in this intermediate from the NH₃ group to the pyridine ring with concomitant breaking of the S-B bond regenerates the thiopyridone and closes the catalytic cycle. This step can be described as an inorganic retro-ene reaction.

SUBMITTER: Hasenbeck M

PROVIDER: S-EPMC7003781 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Efficient Organocatalytic Dehydrogenation of Ammonia Borane.

Hasenbeck Max M Becker Jonathan J Gellrich Urs U

Angewandte Chemie (International ed. in English) 20191210 4

Dehydrogenation of ammonia borane by sterically encumbered pyridones as organocatalysts is reported. With 6-tert-butyl-2-thiopyridone as the catalyst, a turnover frequency (TOF) of 88 h<sup>-1</sup> was achieved. Experimental mechanistic investigations, substantiated by DLPNO-CCSD(T) computations, indicate a mechanistic scenario that commences with the protonation of a B-H bond by the mercaptopyridine form of the catalyst. The reactive intermediate formed by this initial protonation was observed ...[more]

PMID: 31573726

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