Facile bromination of the benzene ring during the cyclisation of the 1 H -3-methyl-4-ethoxycarbonyl-5- -arylidenehydrazonopyrazoles to the 3-substituted-aryl-1 H -6-methyl-7-ethoxycarbonyl- -pyrazolo[3,2-c ]-s-triazoles

1H-3-Substituted-aryl-6-methyl-7-ethoxycarbonyl-pyrazolo[3,2-c ]-s-triazoles 2 , 3 were obtained by the action of the bromine on the 1H-3-methyl-4-ethoxycarbonyl-5-aryllidenehydrazono-pyrazoles 1 and were transformed, after hydrolysis-decarboxylation to 1H-3-substituted-aryl pyrazolo[3,2-c ]-s-triazoles 5 in the azomethyne dyes 6 .


Results and Discussion
The bromine action on the 1H-3-methyl-4-ethoxycarbonyl-5-aryllidenehydrazono-pyrazole 1 in acetic acid in the presence of anhydrous sodium acetate led mainly to the pyrazolo-triazole 2a-e in the case of the substituents X=2-NO 2 1a 1 , 4-NO 2 1b 1 , 2-Cl 1c 1 , 4-CH 3 1d 1 or p-N(CH 3 ) 2 7 and 2-OCH 3 1e. 7In the case of the electron donating groups (OH, OCH 3 ) and utilization of excess of the bromine in the presence of a calculated excess of anhydrous sodium acetate, the obtained pyrazolo triazoles 3n-u are brominated at the benzene ring.The bromination occurs mainly at the activated free positions.In the case of the hydroxy groups, all the activated free positions, related to the hydroxy groups are substituted, but in the case of methoxy groups, only one position is occupied.If the activated positions are not free (1m X=4-OH, Y=3,5-tBu 2 ) the action of the bromine led to pyrazolo-triazole 2m.
In the case of compound 1e the action of one equivalent of the bromine led to 2e 7 whereas the action of two equivalent of the bromine led to 3n and a little quantity of 2e.The two molecular peaks M + (m/z) at 378, 380 confirm monobromination.
Differently, the action of one equivalent of the bromine on the 1j afford to a mixture of 1j 2j and 3t whereas two equivalent of the bromine led to 3t and a little quantity of 2j.The two molecular peaks M + (m/z) at 378, 380 confirm monobromination and 1 H-NMR and 13 C-NMR spectra proved the structure of the 3t.
Also by the action of one equivalent of the bromine on the 1k, a mixture of 1k 2k and 3u was formed, whereas two equivalent of the bromine led to 3u.The two molecular peaks M + (m/z) at 408, 410 confirmed the monobromination and 1 H-NMR and 13 C-NMR spectra proved the structure of the 3u.
In the case of the compounds 1f-i, which contains hydroxy groups, utilization of one equivalent of the bromine led to a mixture of compounds.Use of tree equivalents of the bromine for 1f 1g 1i led to the dibrominated compounds 3o 3p 3s whereas the utilization of four equivalents of the bromine for 1h led to the tribrominated compound 3r.The dibromination was confirmed by the tree molecular peaks M + (m/z) at 442, 444, 446 for 3o, M + (m/z) at 442, 444, 446 for 3p, M + (m/z) at 458, 460, 462 for 3s, and the tribromination by the four molecular peaks M + (m/z) at 520, 522, 524, 526 for 3r.The structures of the compounds 3o-s were confirmed also by 1 H-NMR and 13 C-NMR spectra.
Our preliminary experiments on the hydrolysis of the compounds 3n-u by heating them 30min at 100 °C with concentrated H 2 SO 4 , showed that the acids 4n-u contained variable amounts of the decarboxylated compounds 5n-u and in some cases, the starting material, the esters 3.

Scheme 2
This facile decarboxylation of the compounds 4 to 5 during the hydrolysis with concentrated H 2 SO 4 determined us to try one-pot hydrolysis-decarboxylation of 3n-u to 5n-u by 4-6 hours of refluxing with a solution of 80% H 2 SO 4 in acetic acid, method utilized by us for the previously described hydrolysis-decarboxylation of the compounds 2. 7 The new compounds 5n-u were Experimental Section General Procedures.TLC was performed using aluminium plates precoated with silica gel 60 or 60 F 254 (Merck) and visualized by iodine or UV light (254 nm).Melting points were determined on a Böetius PHMK (Veb Analytik Dresden) apparatus.The NMR spectra were recorded on a Varian Gemini 300 and Bruker DRX 400 spectrometer at 25 ºC, unless otherwise stated. 1 H-and 13 C-NMR signals were referenced to TMS and the solvent shift ((CD 3 ) 2 SO δ H 2.50 and δ C 39.5).Coupling constants are given in Hz and without sign.The IR-spectra were recorded (KBr) on a Jasco FT/IR-410 instrument; the UV−VIS spectra were recorded (CH 3 OH) on a M40 Karl Zeiss Jena instrument.Mass spectrometry was carried out on a Varian FINNIGAN MAT 212 instrument and the elementar analysis on the Perkin Elmer 240 instrument.