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

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

Name thesis:degree_name

Master of Science (M.S.)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Chemistry

Year dc:date.available

2020

Author dc:creator

• Mitchell, Joshua K

Contributors dc:contributor

• Mahesh Lakshman
• Barbara Zajc

• hydrogenation
• two-chamber
• deuteriation
• catalytic reduction
• sodium borohydride
• bench-scale
• Chemistry
• Organic Chemistry

Repository record dc:identifier

https://academicworks.cuny.edu/cc_etds_theses/853

OAI identifier oai:identifier

oai:academicworks.cuny.edu:cc_etds_theses-1955