Oxidation of isoxazolidines with peroxy acids. Nitrones and N-hydroxy-1,3-tetrahydrooxazines

Abstract

From 4. A mixture of NaOH (1.65 g, 41.3 mmol) and the ester 4 (10.0 g, 38.5 mmol) in 500 ml of water was heated at about 70 °C for 5 h, during which time most of the solid dissolved. The reaction mixture was cooled and filtered, and the filtrate was acidified with concentrated HC1. The resulting mixture was heated to boiling and then filtered while hot. and the collected solid was washed with water and dried in a vacuum oven to yield 4-oxo-4H-[l,3]thiazino[3,2a]benzimidazole-2-carboxylic acid; 8.86 g (93%); mp 230-232 °C dec; IR 5.84 µ , NMR (Me»SO-d«) 8.3 (m, 1), 7,8-7.3 (m, 3), 7.27 (s, li.

Welwitindolinone C synthetic studies. Construction of the welwitindolinone carbon skeleton via a transannular nitrone cycloaddition

“…Regarding the latter, the use of N- benzyl hydroxylamine (Scheme 4) is representative of several variations which were explored and found to either resist cycloaddition or give large amounts of oxazole side-products via dehydration of the intermediate nitrone (i.e., 18 ) 29,30. Eventually a more satisfactory solution that allowed advancement of the N -methylhydroxylamine adducts was implemented ( vide infra ) 23,24,31,25,26…”

Nitroxide decomposition: Implications toward nitroxide design for applications in living free‐radical polymerization

“…Ali and Wazeer 178 and others 179 have shown that oxammonium compounds are intermediates in the preparation of nitrones by the oxidation of the corresponding hydroxylamines. Rychnovsky et al 18 showed that TEMPO can be oxidized to the corresponding oxammonium and reduced to the corresponding hydroxylamine anion electrochemically.…”

A Concise and Flexible Synthesis of the Core Structure of Pinnaic Acid

“…Multigram quantities of isoxazolidine 8 were synthesised in five steps from 1,5-dibromopentane utilizing the synthetic route developed by Gossinger et al 8 After some experimentation it was discovered that oxidative cleavage of 8 to give nitrone 5 could be effected in high yield by dropwise addition of a solution of MCPBA in dichloromethane at 0°C over a period of seven hours (Equation 1). 9,10 While nitrone 5 decomposes over a period of two days at room temperature it may be stored for up to five months in a freezer.…”