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DOI: 10.1055/s-2002-32950
Tandem Oxidation Processes: The Direct Conversion of Activated Alcohols into Nitriles
Publikationsverlauf
Publikationsdatum:
25. Juli 2002 (online)
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Abstract
The direct conversion of primary alcohols into nitriles is reported (RCH2OH into RCN) using manganese dioxide and ammonia in 2-propanol-THF, containing magnesium sulfate at room temperature. This transformation, which proceeds via an in situ oxidation-imination-aldimine oxidation sequence, has been applied to a range of benzylic, heterocyclic, allylic and propargylic alcohols.
Key words
oxidation - imines - nitriles - cyanides - one-pot
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References
For other tandem oxidation processes see the preceding and following papers in this series.
6The products, which are all known, gave consistent spectroscopic data (and mps if solids).
7Representative experimental: A 2 M solution of ammonia in 2-propanol (2.2 mL, 4.28 mmol; Aldrich) and anhydrous magnesium sulfate (1.93 g, 16.0 mmol) were added to a stirred solution of 4-bromobenzyl alcohol (0.200 g, 1.07 mmol) in THF (4.3 mL). Activated manganese dioxide (Aldrich 21764-6; 1.40 g, 16.10 mmol) was added to the solution. The resulting mixture was stirred at room temperature for 18 hours and then diluted with dichloro-methane (20 mL). The mixture was filtered through Celite®, the Celite® washed well with dichloromethane and the combined filtrates concentrated under reduced pressure. The solid residue was purified by column chromatography (silica gel, EtOAc-petroleum ether, 1:4) to give 4-bromobenzo-nitrile (157 mg, 81%) as a white solid, mp 112.8 °C, published mp (Aldrich) 112-114 °C.
8Treatment of 2-cyanopyridine with ammonia in 2-propanol and THF containing magnesium sulfate and manganese dioxide at r.t. for 18 hours gave unreacted nitrile (30%) and carboxamide (50%). The fact that the nitrile appears to be formed first and is then converted into the carboxamide, appears to rule out a mechanism involving oxidation of an intermediate RCH(OH)NH2 species.
9Carboxamides were also observed with furan- and thio-phene-methanols.