Fast, easy oxidation of alcohols using an oxoammonium salt bearing the nitrate anion

Oxidation of Alcohols to Aldehydes and Ketones Using a Catalytic Pairing of a Nitroxide and Nitric Acid

“…6 When employing 4 , the nitrate anion analogue of 1 , it is possible to oxidize alcohols to the corresponding carbonyl compounds very effectively. 7 8 9 These transformations can be performed using 0.5–0.6 equiv of 4 and the substrate scope proves to be quite broad. The reactions can be performed in solvent with silica gel as an additive (Scheme 1a ) 9 or under solvent-free or mechanochemical conditions without the need for additives (Scheme 1b ).…”

“…The reactions can be performed in solvent with silica gel as an additive (Scheme 1a ) 9 or under solvent-free or mechanochemical conditions without the need for additives (Scheme 1b ). 7…”

“…In order to optimize reaction conditions for the oxidation of alcohols to aldehydes and ketones, we decided to use 1-octanol ( 5a ) as a model substrate. As a starting point, we chose reaction conditions similar to those employed in our other oxidative transformations using 4 , 7 9 but this time starting with 3 . We chose to use 2 mmol of the alcohol substrate, 0.3 equiv of 3 , in 2 mL of dichloromethane, and heating the reaction mixture at 55 °C for 3 h. With the addition of 0.4 equiv of nitric acid, we observed a 69% conversion into 1-octanal ( 6a ) along with 12% of the nitroso intermediate ( 7a ) and 8% of octanoic acid ( 8a , Table 1 , entry 1).…”

“…The reactions can be performed in solvent with silica gel as an additive (Scheme 1a) 9 or under solvent-free or mechanochemical conditions without the need for additives (Scheme 1b). 7 In 4, the nitrate counterion is not innocent and instead plays a role in the reaction mechanism. 7,9 This is not totally unexpected.…”

“…7 In 4, the nitrate counterion is not innocent and instead plays a role in the reaction mechanism. 7,9 This is not totally unexpected. There is precedent for the oxidation of alcohols in a catalytic manner using nitroxides in the presence of nitrogen oxide (NO x ) co-catalysts, with oxygen being the terminal oxidant (Scheme 1c-e).…”