Structural elucidation of thermolysis products of methyl N-methyl-N-nitrosoanthranilate

Abstract

MethylN-methyl-N-nitrosoanthranilate thermolysis in the vapor and condensed phases gave different coupling products, dimethyl 2,2′-(1,2-dimethylhydrazine-1,2-diyl)dibenzoate and methyl 5-methyl-6-oxo-(5H)-phenanthridine-4-carboxylate, respectively.

A novel pathway for the thermolysis of N-nitrosoanthranilates using flash vacuum pyrolysis leading to 7-aminophthalides

“…Surprisingly, the GC-MS chromatogram of 1a (Fig. S2 in the ESI †) obtained in our lab differed from that described by Miltojević and Radulović: 1 Only minor amounts (ca. 25%, GC-FID peak area) of a dimeric compound (m/z 328 at 11.85 min) were detected, which was different from the dimer 2a, while the major thermolysis product was anthranilate 3a (m/z 165).…”

“…We commenced our studies with the gas-phase thermolysis of 1a under GC-MS and GC-FID conditions (injector: 280°C, column: 50-300°C), which were comparable with those from the study of Miltojević and Radulović (injector: 250°C, column: 70-315°C). 1 However, the heating rate in our experiment was higher (25°C vs. 5°C per minute). Surprisingly, the GC-MS chromatogram of 1a (Fig.…”

“…2 We demonstrate that the FVP of nitrosamines is a convenient method for the generation of nitrogen radicals. In contrast to GC thermolysis, 1 an unexpected disproportionation occurs, which leads to the corresponding anthranilate 3a and 7-(methylamino)phthalide 4a (Scheme 1).…”

“…Miltojević and Radulović have recently reported an interesting thermally induced degradation of methyl N-methyl-N-nitrosoanthranilate under gas chromatography (GC) and preparative (batch) thermolysis conditions (Scheme 1). 1 The outcomes were quite different, although the homolytic cleavage of the N-NO bond was the predominant first step in both transformations. The fate of the obtained methyl N-methylanthranilate free radical during the GC-MS analysis was either a recombination (in the transfer line) to form 2a as major product or proton abstraction from the stationary phase (on the column) to generate methyl N-methyl anthtranilate (3a).…”

“…On the other hand, large-scale thermolysis in a sealed vial at 220°C yielded a highly complex mixture of mostly coupling products. 1 The extensive investigations by Miltojević and Radulović did not include high vacuum conditions, which can be achieved with the technique of flash vacuum pyrolysis (FVP). Here, intermolecular reactions are unlikely to occur and no external source of protons is present.…”