1.2- Diazole

E. Bar Ness, Y. Hadar, Y. Chen, and A. Shanzer, Iron uptake by plants from microbial siderophores—a study with 7 nitrobenz-2oxa-1,3-diazole desferrioxamine as fluorescent ferrioxamine B analog. Plant Physiol. 99 1329 (1992). 

Heterocyclic fluorophores based on the benzoxadiazole nucleous, namely 4-nitrobenz-2-oxa-l,3-diazole (NBD) 14 derivatives/analogs, have been widely used as derivatization reagents for analysis purposes. Examples include the amino- or thiol reactive 4-fluoro-7-nitrobenz-2-oxa-l,3-diazole (NBD-F) 15 and 4-chloro-7-nitrobenz-2-oxa-1,3-diazole (NBD-C1) 16 [45-50] and the thiol-reactive /V-((2-(iodoacetoxy)ethyl)-/V-methyl)amino-7-nitrobenz-2-oxa-1,3-dia-zole (IANBD ester) 17 [51] and 7-chlorobenz-2-oxa-l,3-diazole-4-sulfonate (SBD-C1) 18 [52], NBD-F and NBD-C1 derivatives can be excited at about 470 nm by using the relatively inexpensive and reliable argon ion lasers or newer diode pumped solid state (DPSS) lasers. NBD-F has been used as a labeling tag in various capillary electrophoresis (CE) experiments for amino acids [53-57] including the monitorization of in vivo dynamics of amino acids neurotransmitters [58]. 

Ghosh PB, Whitehouse MW (1968) 7-Chloro-4-nitrobenzo-2-oxa-1,3-diazole A new fluoro-genic reagent for amino acids and other amines. Biochem J 108 155-156... 

A specific and sensitive fluorimetric method was proposed by Al-Majed for the determination of (7))-penicillamine in its pure state and in its dosage forms [24], The method is based on the coupling between (/))-penicillamine and 4-fluoro-7-nitroben-zo-2-oxa-1,3-diazole, and analysis of the fluorescent product was measured at an excitation wavelength of 465 nm and an emission wavelength of 530 nm. The fluorescence intensity was found to be a linear function of the drug concentration over the range of 0.6-3 pg/mL, and the detection limit was 2 ng/mL (13 nM). 

Ramachandram B, Samanta A (1998) Transition metal ion induced fluorescence enhancement of 4-(N,N-dimethylethylenediamino)-7-nitrobenz-2-oxa-1,3-diazole. J Phys Chem A 102 10579-10587... 

The dynamics of lipid movement between the two leaflets of membrane lipid bilayers has been monitored using a variety of phospholipid analogs. Most of the analogs incorporate a reporter group attached to the C-2 of the glycerol moiety. One common substituent is a florescent-labelled fatty acid to form 1,2-(palmitoyl-N-4-nitrobenzo-2-oxa-1,3-diazole-amino-caproyl)... 

The 1,3-diazoles are much less susceptible to electrophilic substitution than pyrrole, furan, and... 

In general, the 1,3-diazoles do not react by nucleophilic substitution, although imidazole can participate in the Chichibabin reaction with substitution at C-2 the position of substitution is eqmvalent to that noted with pyridine (see Section 11.4.1). Nucleophilic species that are strong bases, like... 

Diazol-4-imines (Anhydro-4-amino-lJ-diazolium Hydroxides) (98)... 

Diazole-4-thiones (Anhydro-4-mercapto-l,3-diazolium Hydroxides) (103)... 

Pyrazole and Imidazole. These are five-membered ring heterocycles containing two nitrogens, one basic and one neutral. Two common forms are pyrazole (1,2-diazole) and imidazole (1,3-diazole) both are prone to aromatic hydroxylation. 

NBD-CI, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole MSTFA, N-methyl-N-(trimethylsilyl)trifluoroacetamide BSA, N, O-bis(trimethylsily-l)acetamide MTBSTFA, N-methyl-N-(tetr.-butyldimethylsily)trifluoroacetamide BSTFA, N,0-bis(trimethylsilyl)trifluoroacetamide HFB, heptafluorobutyric acid SFE, supercritical-fluid extraction. 

Diazole,Glyoxo1ine or Imidazole (called Imidazol or Glyoxalin in Ger),... 

NOTE Higher nitrated derivs of 1,3-Diazole were not found in Beil or in CA thru I96I... 

Ami noimidazole 2-Amino-1,3-diazole or 2>Aminoglyoxaline[lmidazolon -(2)-imid, in Ger], or... 

TT-Electron delocalization in isoxazole seems to be more effective than in oxazole however, isothiazole is less aromatic than thiazole thus it is not a general rule that 1,2-diazoles possess higher aromaticity in comparison with 1,3-diazoles. Oxygen-containing heterocycles are always less aromatic than their sulfur and nitrogen counterparts, e.g. thiazole > imidazole > > oxazole. At the same time, the relative aromaticity of S- and N-containing heterocycles can interchange (pyrazole > isothiazole > isoxazole). 

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