87773-96-4Relevant academic research and scientific papers
Enhanced synthesis of oxo-verdazyl radicals bearing sterically-and electronically-diverse C3-substituents
Bissember, Alex C.,Canty, Allan J.,Cox, Nicholas,Duggin, Margot,Fuller, Rebecca O.,Judd, Martyna M.,Moggach, Stephen A.,Taylor, Madeleine R.,Turner, Gemma F.
, p. 10120 - 10138 (2021/12/10)
The synthetic viability of the hydrazine- and phosgene-free synthesis of 1,5-dimethyl oxo-verdazyl radicals has been improved via a detailed study investigating the influence of the aryl substituent on tetrazinanone ring formation. Although it is well established that functionalisation at the C3 position of the tetrazinanone ring does not influence the nature of the radical, it is crucial in applications development. The synthetic route involves a 4-step sequence: Schiff base condensation of a carbohydrazide with an arylaldehyde, alkylation, ring closure then subsequent oxidation to the radical. We found that the presence of strong electron-donating substituents and electron rich heterocycles, result in a significant reduction in yield during both the alkylation and ring closure steps. This can, in part, be alleviated by milder alkylation conditions and further substitution of the aryl group. In comparison, more facile formation of the tetrazine ring was observed with examples containing electron-withdrawing groups and with meta- or para-substitution. Density functional theory suggests that the ring closure proceeds via the formation of an ion pair. Electron paramagnetic resonance spectroscopy provides insight into the precise electronic structure of the radical with small variations in hyperfine coupling constants revealing subtle differences. This journal is
2,4-Dialkyl Substituted Carbono- and Thiocarbonohydrazides, Reactions with Carbonyl Compounds
Neugebauer, Franz Alfred,Fischer, Hans,Siegel, Rolf,Krieger, Claus
, p. 3461 - 3481 (2007/10/02)
2,4-Dialkyl substituted carbono- and thiocarbonohydrazides (4) were prepared from alkylhydrazines and phosgene or thiophosgene.Mono carbonyl compounds reacted with 4 (molar ratio 1:1) to yield hexahydro-1,2,4,5-tetrazines (9, 14; exception 13).Aldehydes in excess generally afforded dihydrazones (3); formaldehyde, however, yielded 1,1'-methylenebis(hexahydro-1,2,4,5-tetrazines) (10) as well as the bicyclic compounds 11 and 12.The constitution of 11 was confirmed by X-ray analysis of 11b.Dialdehydes and aliphatic or alicyclic α-diketones reacted with 4 to give double hexahydro-1,2,4,5-tetrazine derivatives (19), aryl substituted α-diketones on the other hand yielded cyclic dihydrazones (15) and/or mono-hexahydro-1,2,4,5-tetrazines (16).
