Date of Award
hydrogenation, two-chamber, deuteriation, catalytic reduction, sodium borohydride, bench-scale
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.
Mitchell, Joshua K., "Reductions by Cobalt-Catalyzed Production of Hydrogen Gas from NaBH4 in a Two-Chamber System" (2020). CUNY Academic Works.
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