1,5-DISUBSTITUTED TETRAZOLES FROM 1-ACETYL-2-para-SUBSTITUTED BENZOYL HYDRAZINES AND p-NITROBENZENEDIAZONIUM CHLORIDE<sup>*1</sup>

Horwitz, Jerome P.; Grakauskas, Vytautas

doi:10.1021/jo01367a007

Cited by 9 publications

(5 citation statements)

References 3 publications

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“…mp 114-115°C (from ethanol) [11]. IR spectrum, ν, cm -1 : 3439, 3123, 3113, 3095, 3067, 3032, 3007, 2925, 2867, 1615, 1599, 1528, 1507, 1493, 1456, 1427, 1381, 1363, 1347, 1316, 1301, 1280, 1264, 1149, 1113, 1097, 1081, 1074, 1040, 1028, 1012, 1002, 987, 963, 894 13 C NMR spectrum (acetone-d 6 ), δ C , ppm: 31.06 (CH 2 ), 120.72…”

Section: -Benzyl-1-(4-nitrophenyl)tetrazole (Iib)mentioning

confidence: 99%

Microwave-assisted arylation of 5-substituted tetrazoles

2010

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SHORT COMMUNICATIONSDespite considerable interest in 2,5-disubstituted tetrazoles as potential substrates for the synthesis of biologically active substances, methods for their preparation have been developed to insufficient extent. Arylation of tetrazole and 5-substituted tetrazoles is one of the least studied reactions of these compounds. On the other hand, it may underlie a promising procedure for the preparation of difficultly accessible 2-substituted tetrazoles. Known methods for arylation of 5-substituted tetrazoles [1, 2] lead to formation of mixtures of isomeric 1,5-and 2,5-disubstituted derivatives. However, in some cases such reactions are characterized by high selectivity. For example, the arylation of 5-substituted tetrazolates [3-6] with diaryliodonium salts in the presence of different catalysts gives only 2,5-disubstituted tetrazoles. The arylation of 5-aryltetrazoles with 2,4-dinitrofluorobenzene also occurs at the 2-position of the tetrazole ring with high selectivity [7].In continuation of our studies on the synthesis of functionally substituted tetrazoles under conditions of microwave activation [8,9], we examined arylation of 5-aryl(alkyl)tetrazoles with 4-nitrofluorobenzene in DMF in the presence of sodium hydroxide under microwave irradiation. We previously showed [2] that the arylation of 5-methylsulfanyltetrazole with 4-nitrofluorobenzene in DMF in the presence of sodium hydroxide yields a mixture of 1,5-and 2,5-disubstituted isomers. However, no arylation of 5-alkyl-or 5-aryltetrazoles occurred under analogous conditions despite microwave activation or conventional heating. Obviously, the reason is low nucleophilicity of tetrazolate ion and competing reaction of 4-nitrofluorobenzene with DMF.We presumed that arylation of 5-alkyl(aryl)tetrazoles could be accomplished in another polar solvent, dimethyl sulfoxide. In fact, the arylation of 5-aryltetrazoles with 4-nitrofluorobenzene in DMSO in the presence of sodium hydroxide under microwave activation or without it (on heating) gave only the corresponding 2,5-diaryltetrazoles. Our results showed that microwave irradiation increases the yield of the arylation products by a factor of 1.5 to 3. Below are given the yields of 2,5-diaryltetrazoles IIId-IIIg obtained in microwave-assisted reaction and under conventional heating, respectively, %: IIId, 55, 40; IIIe, 77, 40; IIIf, 67, 40; IIIg, 60, 21. High yields of the arylation products under microwave activation made it possible to simplify the isolation procedure and avoid additional purification. Thus microwave-assisted arylation of 5-aryltetrazoles with 4-nitrofluorobenzene in DMSO in the presence of sodium hydroxide may be regarded as one of the simplest and effective procedures for the synthesis of 2,5-diaryltetrazoles.The arylation of 5-methyl-, 5-benzyl-, and 5-(4-chlorobenzyl)tetrazoles in all cases afforded mixtures of isomeric 1-and 2-aryl-5-alkyltetrazoles. The ratio of isomeric tetrazoles IIa : IIIa was 2 : 3, and the R = Me (a), PhCH 2 (b), 4-ClC 6 H 4 CH 2

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Section: -Benzyl-1-(4-nitrophenyl)tetrazole (Iib)mentioning

confidence: 99%

Microwave-assisted arylation of 5-substituted tetrazoles

2010

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“…The carbodi-imides were prepared in high yield from the corresponding thioureas by treatment with 2-chloro-l-methylpyridinium iodide and triethylamine, as before. They were thermally much more stable than the analogous benzene derivative (8), presumably because the initial, favourable electrocyclic reaction proposed for (8) is not possible in (24) and would have a much higher activation energy in (25). The carbodi-imides were unchanged when heated for several hours in boiling 1,2,4-trichlorobenzene, and they gave complex mixtures when heated in the melt at 270 "C under nitrogen; they were therefore subjected to flash vacuum pyrolysis.…”

Section: Extensions Of This Nitro Groupcarbodi-imide Interaction-mentioning

confidence: 99%

“…The intermediate (26) could then rearrange to (27), as shown, possibly via a fused tetracyclic system. Interaction between the carbodi-imide and nitro groups could also be favoured by the known propensity for 2,2'-substituted biphenyls to adopt the cisoid conformation in the gaseous and condensed phases.22 Some evidence for the decisive influence of the nitro group in the pyrolysis of (25) was found in the flash vacuum pyrolysis of the compound with the nitro group omitted: when biphenyl-2yl(pheny1)carbodi-imide was pyrolysed under exactly the same conditions as (25), it was recovered largely unchanged and only 4% of the cyclisation product, 6-anilinophenanthridine, was obtained. Thus the nitro group in (25) controls the direction of ring closure and provides a lower energy pathway for it, as in the mechanism proposed.…”

Section: Extensions Of This Nitro Groupcarbodi-imide Interaction-mentioning

confidence: 99%

“…After 5 h, 10 mg of (24) had sublimed. An orange compound was washed with methylene chloride from the cold finger and removal of the solvent gave a solid which was crystallised from petroleum (60-80 "C) to give benz [1,8-cd] 2'-Nitrobipheny1-2-yI(phenyl)carbodi-imide (25).-The carbodi-imide (25) (248 mg), prepared from the thiourea (method B), was sublimed through a quartz tube at 750 "C/0.015 mmHg, to give a polar solid (90 mg) which crystallised from petroleum-dichloromethane and then sublimed to give benzimidazoC 1,2--phenanthridine (29) (45%) identical with an authentic specimen prepared as follows.…”

Section: -Nitrophenylmentioning

confidence: 99%

“…The key intermediate, 2-phenyl-l,2,4-benzotriazin-3-one 1oxide (19), has been isolated from a careful thermolysis of (12) in toluene; in solution it is in reversible equilibrium with the ring-opened form (20). This new nitro-carbodi-imide group interaction has been extended to the more stable nitrobiphenyl(pheny1)carbodi-imide (25) and nitronaphthyl(pheny1)carbodi-imide (24) which, on flash vacuum pyrolysis, give benzimidazo[l,2-f)phenanthridine (29) and benz[cd] indazole 1 -oxide (32) respectively, in new rearrangements.…”

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confidence: 99%

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