Benzo selenadiazoles

The preparation of quinoxaline derivatives carrying a substituent in the benzene ring requires suitably substituted o-phenylenediamines. These have been prepared by reductive cleavage (SnCl2) of appropriately substituted 2,1,3-benzoselenadiazoles (I9).21 Benzo-selenadiazoles, readily prepared from 1,2-diaminobenzenes and selenium dioxide, undergo halogenation at positions 4 and 7 and sulfonation at C-4. 5,6-Dichloro- 2,3-diphenylquinoxaline has been synthesized from benzil and l,2-diamino-3,4-dichlorobenzene, the diamine in turn was obtained from 4,5-dichloro-2,l,3-benzoselenadiazole.22... 

Entry into the benzo-l,3-diselena-2-selone (196) series is possible by heating 1,2,3-benzo-selenadiazole (195) with CSej <83CC295> (preparation of carbondiselenide, see Equation (19) <72IJS(A)133,81IC856>. 

Dibenzotetraselenafulvalene can be prepared by this method starting from 1,2,3-benzo-selenadiazole and subsequent coupling of the resulting benzo-l,3-diselenole-2-selone with triphenyl phosphine in 66% yield <83CC295>. Likewise, the parent 2-methylene-1,3-diselenole (27) can be obtained from acetaldehyde semicarbazone after ring closure and subsequent treatment of the 1,2,3-selenadiazole (185) with potassium t-butoxide (selenadiazole route, see Scheme 49) <87TL5635>. 

CH2CHNH2CO2H] The complexes were characterized by i.r., u.v., and n.m.r. spectra. The ground- and excited-state configurations of the electrons of 4-substituted benzothiadiazoles (295 X = S R = H, NH2, or OH) were calculated the 7r-/a-bonds, total energies, and heats of atomization of (295), their protonated forms, and their tautomers were tabulated. The hydroxy-and amino-tautomers are more stable than the 0x0- and imino-tautomers, respectively. Compounds (295) are protonated on N-1. The linear dichroism and m.c.d. spectra of 2,1,3-benzothiadiazole and 2,1,3-benzo-selenadiazole were measured and c.d. spectra reported for the j3-cyclodextrin compound with the heterocycle. The kinetics of formation and equilibrium data have been reported for the Meisenheimer complexes of the benzothia- and benzoselena-diazoles (295 X = S, or Se R = 4-NO2) with MeO" in MeOH/DMSO. ... 

Benzoselenolo[2,3-ii]benzoselenophenes synthesis, 4, 116, 1078 Benzoselenolopyrylium cations oxidative ring contraction, 4, 969 [l]Benzoselenolo[3,4-ii][l,2,3]selenadiazoles synthesis, 6, 354 Benzo[h]selenophene, 2-acetyl-synthesis, 4, 966 Benzo[h]selenophene, 2-bromo-acylation, 4, 948... 

A general route to benzo-2,l,3-selenadiazoles involves the condensation reaction between 1,2-diaminobenzene and selenium tetrachloride. This method has also been used recently for the synthesis of 4,5,6,7-tetrafluoro-2,l,3-benzotelluradiazole (Eq. 2.9) ... 

This section will focus primarily on a comparison of these ring systems with their heavier chalcogen analogues. The first selenium derivative benzo-l,2,5-selenadiazole was prepared more than 115 years ago by the condensation reaction of selenium dioxide with 1,2-diaminobenzene (Eq. 11.12) and other benzo derivatives may be prepared in a similar manner. The parent 1,2,5-selenadiazole has also been reported. This reagent has been employed to make the tellurium analogue via treatment with ethylmagnesium bromide followed by the addition of tellurium tetrachloride (Eq. 11.13). ... 

The structure of the isomeric benzo-l,2,3-thiadiazole 11.30 is unknown, but the 1 1 adduct with AsFs (11.31) has been structurally characterized. The AsFs molecule is coordinated to the carbon-bonded nitrogen atom. Cycloocteno-l,2,3-selenadiazole is an effective source of selenium for the production of semi-conductors such as cadmium selenide." ... 

Die Elektrolyse von Benzo-l,2,5-thiadiazol bzw. -selenadiazol in waBriger Losung an Quecksilber fiihrt ebenfalls zu 1,2-Diamino-benzol4 ... 

One of the frequently discussed problems is the coordination mode in complexes of benzo-2,l,3-thiadiazole (A = S) and its selenium analogue (A = Se), (174) or (175) (72ZOB592, 72ZOB2049). X-ray studies indicate that only the N-M coordination (174) is realized. The same mode is characteristic for the complexes of 1,2,3-thiadiazole and 1,2,3-selenadiazole (176). However, the X-ray analysis shows that the coordination via the A atom cannot be excluded, e.g., tellurium may serve as the donor site in the... 

The decreasing order of aromaticity based on DRE values (in kcal mol"1) is benzene (22.6) > thiophene (6.5) > selenophene > pyrrole (5.3) > tellurophene > furan (4.3). In benzoderivatives the effect of the heteroatom is similar to the azole series and the decreasing scale of aromaticity is benzo-2,l,3-selenadiazole > benzo-2,1,3-thiadiazole > benzo-2,l,3-oxadiazole [28],... 

Only a few works on the synthesis of 1,3,4- and 1,2,5-diazoles have been reported, all in older literature [6,14], More attention has been paid to synthesis of benzo-2,l,3-selenadiazoles simply obtained by reaction of aromatic or heteroaromatic 1,2-diamines with selenium dioxide [196-199],... 

The valuable synthetic intermediates are benzo-2,l,3-selenadiazoles. They were used for preparation of. V-al ky I-1,2-benzenediamines, 3-nitro-1,2-benzenediamines, 3,4-diamino-2-nitrophenols, and 5-nitroqunoxalines. The key step of the reaction is their reductive deselenation with hydrogen iodide or, better, with ammonium hydrosulfide [233-238],... 

Disubstituted 1,2,4-selenadiazoles reacted with DMAD with extrusion of selenium to give pyrimidine-5,6-dicarboxylates, while 1,2,5-selenadiazoles produce pyrazines. In a similar way, quinoxaline can be obtained from benzo-2,1,3-selenadiazoles [6, 110]. (For deselenation see also Sect. 3.4). 

NaNC>3 and cone. H2SC>4 gave 5-chloro I-nitrobenzo[2,l,3]selenadiazole 142 in 90% yield (Equation 7) <2004RJC428>. An improved method for nitration of fluorine-substituted benzo[2,l,3]selenadiazoles was also reported. Treatment of a variety of benzo[2,l,3]selenadiazoles with commercially available 90% nitric acid dissolved in a mixture of methanesulfonic acid and phosphorus pentoxide at room temperature gave 4-nitrobenzo[2,l,3]sclc-nadiazoles in 81-94% yield <2004JHC1023>. The obtained 2,1,3-benzoselenadiazoles were used as precursors to o-phenylenediamines (see Section 6.12.5.8). 

Benzoselenadiazoles were synthesized at room temperature in the solid state with ortho-aromatic diamines and selenium dioxide. Diamines and selenium dioxide were ground, respectively, and then were mixed in a ratio of 1 1 in a mortar at room temperature the process was monitored with X-ray diffraction (XRD) or IR. The results showed that the reactions were completed after 30 min of grinding and the desired products were obtained. The yields of the synthesized compounds are as follows 2,1,3-benzoselenadiazole 196 77% l,2,5-selenadiazolo-[3,4-A]pyridine 284 44% l,2,5-selenadiazolo[3,4-c]pyridine 285 23% 5-methyl-2,l,3-benzo-[3,4-c]selenadiazole 286 74% 1,2,5-selenadi-azole[3,4- /]pyrimidine-7-(6/7)-one 287 50% 5,7-dihydroxy-l,2,5-selenadiazolo-[3,4- 7]pyrimidine 288 19% and 2,l,3-naphtho-[2,3-c]-selenadiazole (289) 77% <2004MI1>. 

Reaction of diamine 290 with selenium oxychloride in refluxing chloroform-pyridine gave benzo[ 1,2- 3,4-c ]bis[ 1,2,5]-selenadiazole 84 and [l,2,5]selenadiazolo[3,4-c]-2,l,3-benzothiazole 85 in quantitative yields (Equation 38) <2004JHC955>. The yield of product 85 improved compared to the reaction of diamine 290 with Se02. 

A large body of information on the methods of synthesis, application, structure, and properties of all known five-membered nitroazoles - pyrazoles, imidazoles, triazoles, tetrazoles, oxazoles, isoxazoles, oxadiazoles, thiazoles, isothiazoles, thiadiazoles, selenazoles, selenadiazoles, and their benzo analogs - indazoles, benzimidazoles, benzoxazoles, benzisoxazoles, benzoxadiazoles, benzothiazoles, benzoisothiazoles, benzothiadiazoles, benzotriazoles, benzoselenazoles, and ben-zoselenadiazoles has been systematized, summarized, and critically discussed in this monograph. 

The only evidence for the existence of a selenonitroso intermediate is provided by U V spectra of the photolysate of benzo[c] 1,2,5-selenadiazole-2-oxide (126) in a matrix at 100K. Spectra are consistent with the formation of 128 (79TL745). Telluronitroso compounds, RN=Te, are unknown. 

---