Syntheses of 3-(substituted)-2,4,6-triphenylverdazyls

Abstract

DURST, RUIXLN XU, and NARESH S. DALAL. Can. J. Chem. 72, 1849Chem. 72, (1994.Two series of 2,4,6-triphenylverdazyls substituted at the C(3) position of the heterocyclic ring are obtained using new convenient synthetic methodology. Thus, crown ether assisted solid-liquid phase-transfer catalysis promotes the formation of 3-nalkyl-substituted 2,4,6-triphenylverdazyls in the reactions of 1,3,5-triphenylformazan with n-alkyl bromides. Under PTC conditions, methylation of 3-(4-nitropheny1)-1,5-diphenylformazan with methyl iodide exclusively gives the corresponding verdazyl radical. 3-Substituted 2,4,6-triphenylverdazyls containing various di(cyclo)alkylamino moieties at the C (3) Chem. 72,1849Chem. 72, (1994. Faisant appel B une nouvelle mtthodologie de synthbse, on a obtenu deux series de 2,4,6-triphtnylverdazyles substituCs en position C(3) de l'htttrocycle. La catalyse par transfert de phase solide-liquide assistte par un tther-couronne favorise la formation des 3-n-alkyl-2,4,6-triphtnylverdazyles lors des rtactions des 1,3,5-triphtnylformazane avec des bromures de n-alkyles. Dans des conditions de transfert de phase, la mtthylation du 3-(4-nitrophCny1)-1.5-diphtnylformazane par l'iodure de mtthyle conduit uniquement au radical verdazyle correspondant. On a prtpare des 2,4,6-triphtnylverdazyles substituts par des portions di(cyclo)alkylamino en position (C)3 du cycle verdazyle en faisant rtagir du 1,3,5-triphCnylformazane avec les I-[N,Ndi(cyclo)alkylaminomtthyl]benzotriazoles correspondants en prtsence de monohydrate d'hydroxyde de baryum comme catalyseur efficace. La sonication de cette rtaction permet d'obtenir des rendements beaucoup plus tlevCs de verdazyles. On a synthttist un bis-verdazyle lit aux positions C(3) par deux N. On a caractCrisC tous les radicaux obtenus par des microanalyses, des spectres UV-visible et par spectroscopie RPE.[Traduir par la rtdaction]

Verdazyls and Related Radicals Containing the Hydrazyl [R2N‐NR] Group

“…If formaldehyde is used with an equivalent amount of a secondary amine (e.g., pyrrolidine, piperidine) then 6-aminoverdazyls are produced (Scheme 7.2). 16,17 Reactions of formazans with formaldehyde under acidic conditions give cationic verdazylium salts 12, which can then be reduced to the radicals (Scheme 7.3). 15,18 -20 The verdazylium salts can be generated in situ 12,21 and reduced or they can be isolated.…”

Formazans in the synthesis of heterocycles. II. Synthesis of azines (Review)

“…The chemistry of these types of 1,2,3,4-tetrahydro-1,2,4,5-tetrazines is closely related (Scheme 2) [3,4,7,17]. They are all produced by path a in Scheme 1 in that the N-C bond involving the N-1 nitrogen atom and the carbon atom of the second substituent at the N-5 atom is formed during the cyclization process.…”

“…Until now 5-alkylformazans 6 have only been obtained by the alkylation of formazans. Methyl iodide and alkyl bromides, and more rarely other haloalkanes or dimethyl sulfate, are most often used for these purposes [4,7,17]. As in the alkylation of representatives of other groups of hydrazones, in these cases base catalysis is required, and the reaction takes place with the participation of formazanthiones [2-4, 7, 17].…”

“…The alkyl halides can have a long (up to C 15 H 31 ) or a branched chain and aryl or hetaryl substituents [2][3][4]17]. Thus, if benzyl bromide is used tetraphenylverdazyls 13 are obtained from the formazans 1, and if benzhydrol bromide is used pentaphenylverdazyl 14 is obtained (Scheme 6).…”

“…In place of the mixture of amine and formaldehyde it is also possible to use aminomethylal Me 2 NCH 2 NMe 2 [7]. In its place Katritzky and co-workers proposed to use 1-(dialkylaminomethyl)benzotriazoles (Btz 1 NRR 1 ) (Scheme 8) [17]. This made it possible to greatly diversify the nature of the substituents in the targeted verdazyls 23 since symmetrical and unsymmetrical dialkylamino [methylbenzylamino, methyl(2-furyl)amino, etc.]…”