Premium
Reactivity of 3‐alkyl‐4‐arylazomethylene‐3,4‐dihydro‐1,2,3‐benzotriazines in protic solvents: 1,4‐Addition reactions and dimroth rearrangement
Author(s) -
Vaughan Keith,
LaFrance Ronald J.,
Tang York,
Hooper Donald L.
Publication year - 1991
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570280711
Subject(s) - chemistry , substituent , ring (chemistry) , alkyl , methanol , medicinal chemistry , aryl , ethanol , reactivity (psychology) , organic chemistry , medicine , alternative medicine , pathology
3‐Alkyl‐4‐arylazomethylene‐3,4‐dihydro‐1,2,3‐benzotriazines 5a and 5b undergo facile 1,4‐addition of methanol or ethanol to afford stable crystalline hydrazones, 6 and 8 which have been characterised by spectroscopic analysis. In particular, the nmr spectrum of 8 shows novel features due to the diastereotopic nature of the CH 2 protons in the two O‐ethyl groups. Compound 5b shows a property unique to the compounds in this series; refluxing this arylazomethylenetriazine in ethanol affords a rearranged product, characterised as the 1‐aryl‐2‐cinnolinylhydrazine ( 9 ). The formation of 9 is rationalised as a ring opening‐ring closure process analogous to the Dimroth rearrangement. The cinnoline 9 displays some novel chemistry arising from the facility of the arylhydrazino substituent to react with acid to give a fragmentation product, 3‐methylindazole ( 7 ).