2- benzo-1,3-diazole

The benzofuroxtin [benzofurazan oxide, 3,4-benzo-l,2,6-oxa-diazole-2-oxide, or 2,1,3-benzoxadiazole-l-oxide (1)] ring system has been reviewed briefly on several occasions, notably by Kaufman and Picard,Boyer, and Behr. The mqst recent of these covers the literature until 1959, and since that date there have been many advances in the subject. This, we feel, justifies the field being covered once more, and its separation from the monocyclic 1,2,5-oxadiazole oxides—the furoxans. We consider also other furoxano-fused compounds in this chapter, subject to the limitation that the ring adjacent to the furoxan is aromatic and six-membered. 

The properties of the diazotization product of 2-aminothiophenol are completely different from those of 2-aminophenol. In the reaction shown in Scheme 6-44 the diazo-thiophenolate (6.66) is not detected at all. The benzo-l-thia-2,3-diazole (6.67) is the stable product. A comparison of spectral data for diazophenoxide (6.63), benzo-l-oxa-2,3-diazole (6.64), and benzo-l-thia-2,3-diazole (6.67) is given in Section 4.2. The l-thia-2,3-diazole structure was first postulated by Le Fevre et al. (1954) on the basis of infrared spectra. 

Benzopyrazoles, see Indazoles Benzo-l-thia-2,3-diazole 136 f., 192, 225 Benzo-l,2,3-triazene 225 Benzotriazinones 133 f. 

Hydrazino-4-nitro-benzo-2-oxa-l,3-diazole Nbd-H Aldehydes and ketones 611... 

K.R.J. Thomas, J.T. Lin, M. Velusamy, Y. Tao, and C. Chuen, Color tuning in benzo[l,2,5]thia-diazole-based small molecules by amino conjugation/deconjugation bright red light emitting diodes, Adv. Func. Mater., 14 83-90 (2004). 

TV-Aminoethylazoles, which are frequently encountered as intermediates in the preparation of pharmacologically active compounds, are readily obtained by solid liquid phase-transfer catalysed reaction of the azole, diazole or triazole and their benzo derivatives with 2-chloroethylammonium chloride at reflux temperature using a procedure analogous to 5.3.3 [25]. 

In contrast with the azoles, diazoles and their benzo derivatives tend to react with dichlorocarbene to yield the tris(diazolyl)methanes, presumably via the initial formation of the N-dichloromethyl derivative [6, 13]. Only in more activated polymethyl derivatives does reaction occur at a ring carbon atom. In a similar manner (7.7.1.B), 2-chloropyridine and 2-chloroquinoline react with dichlorocarbene at the ring nitrogen atom to yield, after nucleophilic displacement of the chloro group, the 1 -dichloromethyl-2-oxo derivatives (13-25%) [14] (Scheme 7.38). 2-Chlorobenzothiazole reacts in an analogous manner, but other pyridine and quinoline derivatives fail to react. It is also noteworthy that the dichloromethyl group is unusually stable and is not converted into the formyl group. 

Herz salts (89) made from 3-aminopyrazoles (Section 4.11.8.5) give pyrazolo[3,4-r/]-l,2,3-thia-diazoles (90) when subjected to reduction by sodium dithionite followed by nitrozation (Equation (12)) <84JOCl224>. If the reduction is carried out in an inert atmosphere the disulfide (91) is formed which upon nitrozation gives (90) in 63% yield. Notably, benzo-fused Herz salts give benzo-1,2,3-thiadiazoles simply on treatment with nitrozating mixture <84CHEC-I(6)916>. 

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],... 

Primary and secondary amines have been quantitated by thin layer chromatography after derivatization with 7-chloro-4-nitro-benzo-2-oxa-l,3-diazole (NBDC1, 12). The reagent has also been used for analysis of reduced nitrosamines employing adsorptive mode HPLC (13). 

Electronic Structure of Benzo-2,l,3-thia- and -selena-diazoles 523... 

For almost a century, since 2,1,3-benzothiadiazole (1) was discovered by Hinsburg in 1889, the chemistry of 1,2,5-thia- and -selena-diazoles has held considerable interest for organic and physical chemists. Three periods of progress can be distinguished during the first, 1890-1958, interest focused on the synthesis and substitution of benzo derivatives (1)... 

Kinetic studies of reaction rates of the 4- and 5-chloro derivatives of all three benzo-2,1,3-diazoles with methoxide anion show that the 5-chloro compounds are more reactive than the corresponding 4-chloro derivatives (see Section 4.26.3.3). The rates of reaction for the former were in the order O Se > S and for the latter the order was O > Se S. This again underlines the high bond order between C(4) and C(5) and the higher electron density at C(4) compared to that at C(5) (see Section 4.26.4.1) (68SA(A)1869). 

Conductivity measurements on solutions of the salts (4) in anhydrous HC02H show them to be fully dissociated (69ZOR153). Ratios of Js -J s (Table 4) indicate that for 1,2,3-benzodithiazolylium chloride (4 R1 = H), substitution of S(l) by Se has no effect on the aromatic character of the system, whereas similar substitution of S(2) results in greater bond fixation and hence a decrease in aromaticity. This contrasts with data for 1,2,3-benzo-selena-, thia- and -oxa-diazoles (see Section 4.01.4.2.2). 

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. ... 

Sample preparation Condition a Sep-Pak C18 SPE cartridge with 10 mL water, 5 mL MeOH, and 10 mL water. 1 mL Urine -I- 2 nmoles equilin -I- 100 p-L 1.5 M pH 3 acetate buffer, add to the SPE cartridge, wash with 10 mL 150 mM pH 3 acetate buffer, elute with 3 mL MeOH. Add HCl to the eluate so that the concentration of HCl is 500 mM, heat at 100° for 1.5 h, neutralize with sodium bicarbonate, extract with 2 mL chloroform. Evaporate the organic layer to dryness, reconstitute with 1 mL 5 pM 4-chloro-7-nitro-benzo-2-oxa-l,3-diazole (l D-Cl) in MeCN containing 25 nM 18-crown-6 and 15 mM potassium carbonate, heat at 80° for 30 min, filter, inject a 10-15 pL aliquot. 

For increased sensitivity, reagents that yield fluorescent products are employed. These include OPA, fluorescamine, and 4-fluoro-7-nitro-benzo-2-oxa-l, 3-diazole (NBD-F). Derivatization with OPA provides the best limits of detection for most amino acids. Although the products of OPA derivatization are unstable and decompose fairly rapidly to produce nonfluorescent 2,3-dihydro-lH-isoindol-l-ones, this is not a problem with postcolumn derivatization since the products are detected almost instantaneously. 

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