An efficient synthesis of heterocyclic N-oxides over molecular sieve catalysts

Prasad, M. R. N.; Kamalakar, G.; Madhavi, G.; Kulkarni, S. J.; Raghavan, K. V.

doi:10.1039/b003926h

Cited by 28 publications

(9 citation statements)

References 11 publications

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“…Transition‐metal‐catalyzed processes have been also developed 4. Among them Re,4a Ti,4b W,4c Ru4d and V4e are the most commonly employed. The flavin family is the only class of organic molecules utilized as catalysts for the oxidation of aliphatic tertiary amines 5.…”

Section: Introductionmentioning

confidence: 99%

2,2,2‐Trifluoroacetophenone as an Organocatalyst for the Oxidation of Tertiary Amines and Azines to N‐Oxides

Limnios

Kokotos

2013

Chemistry A European J

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A cheap, mild and environmentally friendly oxidation of tertiary amines and azines to the corresponding N-oxides is reported by using polyfluoroalkyl ketones as efficient organocatalysts. 2,2,2-Trifluoroacetophenone was identified as the optimum catalyst for the oxidation of aliphatic tertiary amines and azines. This oxidation is chemoselective and proceeds in high-to-quantitative yields utilizing 10 mol % of the catalyst and H2 O2 as the oxidant.

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Section: Introductionmentioning

confidence: 99%

2,2,2‐Trifluoroacetophenone as an Organocatalyst for the Oxidation of Tertiary Amines and Azines to N‐Oxides

Limnios

Kokotos

2013

Chemistry A European J

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“…Aqueous hydrogen peroxide (H 2 O 2 ) stands out as an ideal oxidant due to its high oxygen content, safety, ease of use, and low production and transportation costs. 7 Compared to other oxidants, such as m-chloroperbenzoic acid (MCPBA), 8 monoperoxyphthalic acid, 9 dioxiranes, 10 and Caro's acid (H 2 SO 5 ), 7 which can generate hazardous waste and byproducts, hydrogen peroxide generates only water as a byproduct. 8 This makes it a more environmentally friendly option for the oxidation processes.…”

Section: ■ Introductionmentioning

confidence: 99%

“…7 Compared to other oxidants, such as m-chloroperbenzoic acid (MCPBA), 8 monoperoxyphthalic acid, 9 dioxiranes, 10 and Caro's acid (H 2 SO 5 ), 7 which can generate hazardous waste and byproducts, hydrogen peroxide generates only water as a byproduct. 8 This makes it a more environmentally friendly option for the oxidation processes. However, the exothermic nature of the reaction and potential hydrogen peroxide decomposition issues must be carefully managed during scale-up production.…”

Section: ■ Introductionmentioning

confidence: 99%

“…10 The catalytic oxidation of 2-hydroxypyridine using a TS-1 molecular sieve catalyst has been employed to synthesize HOPO. 8 While the production of HOPO via this route is economically impractical due to the higher cost of 2hydroxypyridine, the preparation of pyridine-N-oxide through catalytic oxidation still holds significant application potential. 8 Powder catalysts with small sizes and high specific surface areas are used in batch reactions to reduce the influence of internal diffusion effects and improve the contact between the reaction system and the catalyst.…”

Section: ■ Introductionmentioning

confidence: 99%

“…8 While the production of HOPO via this route is economically impractical due to the higher cost of 2hydroxypyridine, the preparation of pyridine-N-oxide through catalytic oxidation still holds significant application potential. 8 Powder catalysts with small sizes and high specific surface areas are used in batch reactions to reduce the influence of internal diffusion effects and improve the contact between the reaction system and the catalyst. 12,13 However, the complexity of separating these catalysts from the reaction system after the reaction may hinder scale-up capability, limit production efficiency, and increase labor costs.…”

Section: ■ Introductionmentioning

confidence: 99%

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Development and Scale-Up of a Fully Continuous Flow Synthesis of 2-Hydroxypyridine-N-oxide

Tao,

Li,

Zuo

et al. 2023

Org. Process Res. Dev.

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A fully continuous flow synthesis of 2-hydroxypyridine-N-oxide (HOPO), an important peptide coupling reagent used in a variety of pharmaceutical ingredient preparations, was designed, developed, and scaled up. The process involved the catalytic oxidation of 2-hydroxypyridine using hydrogen peroxide, followed by quenching and hydrolysis to obtain HOPO in an aqueous solution. A mixed fixed bed reactor was designed featuring a 3D-printed static mixer to achieve the complete conversion of the raw materials, and a continuous post-treatment process involving acid crystallization was developed to obtain a high-quality solid HOPO product. The continuous reaction process and post-treatment process resulted in >90% isolated yield with no need for additional separation and purification steps, thus avoiding an interruption of the continuous reaction. The scale-up process successfully achieved a production rate of 8 kg/day, making this synthesis method highly suitable for industrial applications.

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