Isoquinoline derivatives pyrolysis

A few scattered examples of intramolecular Diels-Alder cycloadditions of nitriles have been documented. Oppolzer has synthesized some benzo-cyclobutene nitriles (Scheme 6-III) and found that on pyrolysis they were transformed into isoquinoline derivatives in excellent yields.10 o-Quinodimethanes are assumed to be transient dienes in all of these cycloadditions. 

The reactions of (174) with various amines has been studied." " Hydrolysis of the hexamine salt of (174) gave not the symmetric diamine but (184) via a cyclic intermediate. The pyrolysis of 5-methyl-2-thenyltrimethyl ammonium hydroxide (185) is claimed to give (186) through a 1,6 Hofmann elimination reaction. The Bischler-Napieralski cyclization has been applied to acetyl derivatives of 2-(2-thienyl) ethylamine and 2-(3-thienyl) ethylamine for the preparation of sulfur analogs of isoquinoline. ... 

Vapor phase pyrolysis of two unsymmetrically substituted 1,2,3-triazole isomers, like (75) and (76), involves the antiaromatic l//-azirine derivative (77) which rearranges to two isomeric 2//-azirines (78) and (79) (71CC1519, 73JCS(Pi)555> and other products. Iminocar-benes (80) are most likely involved as intermediates. Furthermore, nitrogen has been extruded from several IH- 1,2,3-triazoles by flash vacuum pyrolysis. 1-Alkyl-1,2,3-triazoles (81) give nitriles (82) and (83) (via Wolff rearrangement) and (hydroxy)isoquinolines (84) and (85) (by [1,4-H] transfer in the iminocarbene) (75JCS(P1)1). 

New fused tetrazoloazines that have been reported include tetrazolo[5,l-a]isoquinolines,665 tetrazolo[5, l-6]benzothiazoles,666 and tetrazolopyridines.667 Reactions of fused tetrazoloazines, or the azido isomers, that have been reported include hydrolytic cleavage of the pyrimidine ring of tetrazolopyrimidines,66 pyrolysis of 3-azido-pyridazine 2-oxides,66 and photolysis of azido-l,3,5-triazine.670 Dipole moments of 3-azido-1,2,4-triazole derivatives have also been reported.671... 

More recently, Kelemen et al. [154] discussed the pros and cons of XPS, XANES, and N NMR for characterizing and identifying the chemical forms of nitrogen in complex carbonaceous systems. They used both XPS and N NMR quantitatively to study kerogen obtained by demineralization of a Green River oil shale and of a peat sample, as well as chars obtained by pyrolysis and isoquinoline- and quinoline-derived chars. The inherent advantage of using a combination of these methods has thus been demonstrated. 

The thermal reactions that accompany the smoking of tobacco and cannabis furnished important structural information on tobacco alkaloids. The pyrolysis of tobacco alkaloids yielded products such as quinoline and isoquinoline and nicotinonitrile which are probably derived from nornicotine and mysomine. Pyrolysis of natural polyenes such as -carotene yielded ionene and small amounts of toluene, /n-xylene, and 2,6-dimethylnaphthalene. 

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