Nitrogen, elimination

The hydroisoquinolines are more susceptible to ring cleavage than the isoquinolines. Ring cleavage occurs with nitrogen elimination when... 

On the other hand, perfluoro(tetraphenylpyridazines) and some perfluoro(alkyl-pyridazines) undergo nitrogen elimination, or both nitrogen elimination and rearrangement, to give perfluoroalkynes and perfluoropyrimidines (Scheme 7) (74JCS(P1)1513). 

In solvents containing low concentrations of water in acetic acid, dioxane, or sulfolane, most of the alcohol is formed by capture of water with retention of configuradon. This result has been explained as involving a solvent-separated ion pair which would arise as a result of concerted protonation and nitrogen elimination. ... 

The cycloaddition reaction of compound 6 with N-aryl- and N-aralkylazides 23 was also investigated (967(52)7183). Thiadiazabicyclo[3.1.0]hexene derivatives 25 were obtained from the labile triazoline intermediate 24 through nitrogen elimination. This bicyclic system underwent thermal transformation, producing thiadiazine dioxides 26 as the main product together with thiazete dioxides 27 and pyrazoles 28. 

With 2,2 -binaphthyl-3,3 -dicarbaldehyde, however, nitrogen elimination is again observed and only pentaphene is obtained.21... 

Photolytic nitrogen elimination from 8f/-quinazolino[3,2-c][l,2,3]benzotriazin-8-one (1) leads to two intermediates, only one of which can be isolated. When the reaction is performed in the presence of nucleophiles, both intermediates react, via ring enlargement, to provide di-benzo[l,5]diazocines.43 In addition to morpholine and methanol, other alcohols or water can be used as the nucleophile. 

Addition of carbethoxynitrenes to olefinic double bonds occurs readily. Addition of both the singlet and the triplet species can take place, the former stereospecifically, the latter not 49>. Additions of sulphonyl nitrenes to double bonds have not been demonstrated except in two instances in which metals were present. The reason is that either addition of the starting sulphonyl azide to the double bond occurs to give a triazoline that loses nitrogen and yields the same aziridine as would have been obtained by the direct addition of the nitrene to the olefin, or the double bond participates in the nitrogen elimination and a free nitrene is never involved 68>. The copper-catalyzed decomposition of benzenesulphonyl azide in cyclohexene did give the aziridine 56 (15%), which was formulated as an attack by the sulphonyl nitrene-copper complex on the double bond 24>. 

The DA reaction of tetrazines such as 3 was also studied by use of the GS/ MW process [26, 27]. The expected adduct, however, decomposed by nitrogen elimination followed by dehydrogenation, giving a pyridazine or a dihydropyrida-zine [23-25], With 2,3-dimethylbutadiene and cyclopentadiene as dienophiles, SMWI gave dihydropyridazines 8 and 9, as with classical heating [23] (Tab. 7.1, entries 6 and 7). 

The first step of the reaction sequence is the addition of the nucleophilic anion to position 8a of the starting salt 34 to give an intermediate 37 which rapidly undergoes nitrogen elimination to yield the zwitterionic product 38 as a relatively stable brilliant red crystalline substance in high yield. The strong dipolar character of 38 allowed further transformations via 1,3-dipolar cycloadditions and related reactions <2003JOC5652>. 

Derivative 165 was treated with tosyl azide at room temperature for 48 h to give 167. Formation of this product was rationalized by a 1,3-dipolar cycloaddition with participation of the C=C bond in the pyrimidine ring in 165 to form a cycloadduct 166 at first, which underwent a [l,2]-methyl shift and a nitrogen elimination to yield 167. Stmcture elucidation of this product revealed the relative rzr-stereochemistry of the phenyl and methyl substituents. 

The interaction of cyclooctatetraene as a dienophile with the diazadiene, 3,6-bis(trifluo-romethyl)-l,2,4,5-tetrazine 226, is accompanied by nitrogen elimination and gives rise to the 1,1-adduct 227. The latter displays interesting thermal rearrangements depending on the solvent polarity and temperature (equation 73)87. In toluene solution a [l,3]-carbon... 

A direct aza-Wittig cyclization to triazolotriazine 176 (Scheme 67) takes place when triazinone 174 is treated with diphenylthiourea, the latter being substituted on the nitrogen. Elimination of triphenylphosphane sulfide from 175 makes 1,2,4-triazole accessible [86JCS(P1)2037]. When the nucleophilic attack continues on the sulfur, thiadiazoles are formed [86JCS(P1)2037]. 

Kinetic studies showed the rate of nitrogen elimination from compound 4a (Scheme 4) is first order and correlates with the Y value of the solvent (79JOC1717). A slower rate of decomposition was observed in more polar media. This would seem to reflect a greater solvation of starting material, which retards the nitrogen-extrusion process in more polar media. If the intermediate is better represented by 12 rather than 13, nitrogen elimina-... 

An unprecedented nitrogen elimination reaction of 4-amino-7-benzylpyrrolo [23- f][133]triazine-5-caibonitrile (72) to give the pyrrole derivative 74 has been described. The following mechanism, presumably via a a retro Diels-Alder reaction of the imino tautomer 73, has been proposed <990L537>. 

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