Reductions by Cobalt-Catalyzed Production of Hydrogen Gas from NaBH4 in a Two-Chamber System

Author

Joshua K. Mitchell, CUNY City CollegeFollow

Date of Award

2020

Document Type

Thesis

Department

Chemistry

First Advisor

Mahesh Lakshman

Second Advisor

Barbara Zajc

Keywords

hydrogenation, two-chamber, deuteriation, catalytic reduction, sodium borohydride, bench-scale

Abstract

The work outlined in this thesis describes a bench-scale methodology involving a two-chamber system for conducting catalytic hydrogenation reactions by obtaining hydrogen (H₂) gas from stable sodium borohydride (NaBH₄). Whereas NaBH₄ is widely used for a variety of reductions and is known to produce H₂ gas in protic media, to our knowledge, there has been scant use of NaBH₄ in catalytic hydrogenation chemistry where it has been used as a source of H₂ gas. In this work, addition of a catalytic amount of CoCl₂•6H₂O as an aqueous solution to NaBH₄ increases the rate of H₂ gas produced, allowing for efficient H₂ generation and application in catalytic reductions. In the absence of the cobalt catalyst, the formation of H₂ would be retarded by the increased pH of the aqueous NaBH₄ solution. This methodology has several foreseeable advantages. (1) It eschews the need for obtaining and maintaining hazardous compressed hydrogen gas tanks for bench-level reductions. (2) The method can be easily modified for reductions with in situ produced D₂ gas for the deuteriation of diverse organic molecules. (3) Compared to the use of compressed hydrogen gas, the ease of this method and general safety makes catalytic reductions amenable as a learning or synthesis module in undergraduate organic chemistry laboratories.

Using the two-chamber hydrogenation system, reductions of trans-stilbene, 1,1-diphenylethylene, trans-4-phenyl-3-buten-2-one, 9-decen-1-ol, and dicyclopentadiene to the corresponding saturated compounds was achieved. p-Nitroaniline, 1-azido-4-methoxybenzene, and 5-azido-2-methoxypyrimidine were reduced to the corresponding amines. Dehalogenation of 9-bromophenanthrene and 2’,3’,5’-tri-O-(tert-butyldimethylsilyl)-protected 6-chloropurine riboside was achieved. 2,3-Dimethoxybenzaldehyde was reduced to the corresponding alcohol. Reductive aminations were carried out on imines produced in situ from the reactions of 2,3-dimethoxybenzaldehyde with aniline and 2,3-dimethoxybenzaldehyde with (S)-(−)-α-methylbenzylamine. Products obtained in these reactions were analyzed by ¹H and ¹³C NMR.

Recommended Citation

Mitchell, Joshua K., "Reductions by Cobalt-Catalyzed Production of Hydrogen Gas from NaBH4 in a Two-Chamber System" (2020). CUNY Academic Works.
https://academicworks.cuny.edu/cc_etds_theses/853