One‐Pot Direct Oxidation of Primary Amines to Carboxylic Acids through Tandem ortho‐Naphthoquinone‐Catalyzed and TBHP‐Promoted Oxidation Sequence

Abstract

Biomimetic oxidation of primary amines to carboxylic acids has been developed where the copper‐containing amine oxidase (CuAO)‐like o‐NQ‐catalyzed aerobic oxidation was combined with the aldehyde dehydrogenase (ALDH)‐like TBHP‐mediated imine oxidation protocol. Notably, the current tandem oxidation strategy provides a new mechanistic insight into the imine intermediate and the seemingly simple TBHP‐mediated oxidation pathways of imines. The developed metal‐free amine oxidation protocol allows the use of molecular oxygen and TBHP, safe forms of oxidant that may appeal to the industrial application.

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).…”

Primary amines as new carbonyl surrogate in Kabachnik‐fields reaction: A new metal free one pot approach to synthesize α‐Aminophosphonates in water

“…[11] From the last few years, the synthesis of carbonyl compounds from amines has been accomplished using variety of metal catalysts and reagents such as KMnO 4 , ZnCr 2 O 7 , nicotinium dichromate, and palladium, copper and ruthenium. [12][13][14][15][16][17] However, expansion of these methods to construct CÀ C/CÀ N or CÀ P bond in a cascade manner to synthesize value-added products is not much explored and thus is highly desirable. In this regard, we anticipated of converting benzyl amines to aminophosphonates via in situ generation of benzaldehydes by oxidative deamination followed by Kabachnik-fields reaction using H 2 O 2 as a green oxidant.…”

“…Benzyl amines also act as important precursors to produce many synthetic intermediates like imines, oximes, amides and nitriles [11] . From the last few years, the synthesis of carbonyl compounds from amines has been accomplished using variety of metal catalysts and reagents such as KMnO 4 , ZnCr 2 O 7 , nicotinium dichromate, and palladium, copper and ruthenium [12–17] . However, expansion of these methods to construct C−C/C−N or C−P bond in a cascade manner to synthesize value‐added products is not much explored and thus is highly desirable.…”

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

“…The substituted naphthalene-1,2-diols are a redox-active chemical species under aerobic conditions, readily generating ortho -naphthoquinones ( o -NQs) with thermal and chemical stability . To capitalize on the redox process of o -NQs, the aerobic oxidations of amines to imines, aldehydes and ketones, N-nitrosoamines, and carboxylic acids have been explored. Given that the o -NQ catalysts are compatible under both acidic and basic conditions, Ito and Fukuzumi’s biomimetic ADH activity via the hemiacetal mechanistic proposal was explored with the o -NQ catalyst system.…”