Bioinspired o-Naphthoquinone-Catalyzed Aerobic Oxidation of Alcohols to Aldehydes and Ketones

Abstract

A biomimetic alcohol dehydrogenase (ADH)-like oxidation protocol was developed using an ortho-naphthoquinone catalyst in the presence of a catalytic amount of base. The developed organocatalytic aerobic oxidation protocol proceeds through the intramolecular 1,5-hydrogen atom transfer of naphthalene alkoxide intermediates, a mechanistically distinctive feature from the previous alcohol dehydrogenase mimics that require metals in the active form of catalysts. The ADH-like aerobic oxidation protocol should provide green alternatives to the existing stoichiometric and metal-catalyzed alcohol oxidation reactions.

Cu(OTf)2‐Catalyzed Aerobic Cycloisomerization of Alkenyl Sulfones to Furans Using (E)‐β‐Chlorovinyl Ketones and Sodium Sulfinates

“…The reductive elimination of copper(0) species from the intermediate C establishes the synthetic route to 3‐sulfonyl furan 4 , and the aerobic oxidation of Cu(0) to Cu(II) reinstates the catalytic activity of Cu(OTf) 2 [22] . The possibility of H 2 O 2 by‐product formation from the Cu(II)−Cu(0) redox process was ruled out since the 1 H NMR and GC analysis as well as the in situ epoxidation of chalcone failed [23] . The requirement of only $${{ 1/2 }}$$ equivalent of molecular oxygen might explain that the Cu(OTf) 2 ‐catalyzed aerobic cycloisomerization worked well under argon atmosphere even with a residual amount of oxygen in the reaction (entry 14, Table 1).…”

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

“…A biomimetic oxidation of benzyl alcohols was developed using o-naphthoquinone [129] (Scheme 28). The reaction shows regioselectivity toward benzylic alcohol oxidation.…”

ortho-Naphthoquinone-Catalyzed Aerobic Hydrodeamination of Aryl Amines via in Situ De-diazotization of Aryl Diazonium Species

“…Our attempts to influence the hydrode-diazotization process of diazonium intermediate G using p -TSA and BINOL-derived phosphoric acid were not successful, leading to significantly low yields of 2a (20–30%), possibly due to the slow N-nitrosation of aniline nitrogen with reduced Lewis basicity in the presence of acids. The aerobic oxidation of naphthalene-1,2-diol C to o -NQ2 has been well established in previous oxidation reactions. − Since the current hydrode-diazotization reaction proceeded in the absence of o -NQ2 catalyst, it is possible that heating i -PrNO 2 in open air initiates rearrangement to the isopropyl nitrite that also fragments to acetone and nitroxyl . The generation of nitroxyl from i -PrNO 2 may also explain the observed hydrodeamination product 2 from the treatment with i -PrNO 2 only, while accounting for a minor pathway.…”

“…Motivated by the successful biomimetic redox processes of o -NQs in the aerobic oxidations of amines to imines, aldehydes and ketones, N-nitrosoamines, and carboxylic acids, as well as the oxidation of alcohols, the oxidation pathway of 2-aminobiphenyl 1a was examined in open air (Table ). Upon heating the mixture of 1a and 25 equiv of 2-nitropropane ( i -PrNO 2 ) at 110 °C in the presence of 15 mol % of o -NQ1, the desired hydrodeamination product 2a was obtained in 59% yield (entry 1).…”

“…15 While the organic nitrites-promoted hydrode-diazotization strategy appears to be beneficial over the traditional diazotization reagent NaNO 2 in acidic medium (with H 3 PO 2 , 16 NaHSO 3 , 17 CHCl 3 /CF 3 CO 2 H 18 ), the controlled generation of highly reactive diazonium species during the diazotization/ dediazotization process remains an unsolved problem in the area of diazonium chemistry. The recently developed hydrodeamination reagents such as Levin's anomeric amide 19 Motivated by the successful biomimetic redox processes of o-NQs in the aerobic oxidations of amines to imines, 21 aldehydes and ketones, 22 N-nitrosoamines, 23 and carboxylic acids, 24 as well as the oxidation of alcohols, 25 the oxidation pathway of 2-aminobiphenyl 1a was examined in open air (Table 1). Upon heating the mixture of 1a and 25 equiv of 2nitropropane (i-PrNO 2 ) at 110 °C in the presence of 15 mol % of o-NQ1, the desired hydrodeamination product 2a was obtained in 59% yield (entry 1).…”