1 indazoles, flash vacuum pyrolysis

Under flash vacuum pyrolysis conditions 1- and 2-(l-adamantyl)indazoles as well as 1-, 2- and 3-tritylindazoles are mutually interconverted (91BSF592, 89BSB349). 

Flash vacuum pyrolysis of 1- (71), 2- (72) and 3-tritylindazole (73) was carried out at 300 °C and 400°C. The experimental results show that (73) isomerizes to (71) and (72) (72) isomerizes to (71) at 300°C, and (71) remains unchanged at 300°C and at 400°C gives (72) and by-products <89BSB349>. A reaction profile consistent with these observations was proposed which involves indazole aromatic and nonaromatic (3H) tautomers. Under FVP conditions iV-adamantylindazoles (59) and (60) interconverted mutually <91BSF592>. 

Flash vacuum pyrolysis of 5-(2-furyl)-2-phenyltetrazole (667) at ca. 400 °C yields the indazole (670), whereas at higher temperatures the benzofulvene (671) is obtained. The authors have suggested that (668) and (669) are key intermediates in these reactions. Another intriguing process is the formation of 2-phenylbenzotriazole (675) when the tetrazole (672) is thermolysed the proposed mechanism (see Scheme 8) receives support from the isolation of the benzotriazinone oxide (673b) and the spectroscopic detection of the isocyanate (614). ... 

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