L- benzotriazole

Benzotriazole can exist in two tautomeric forms, l-//-benzotriazole (6.46, R = H) and 2-/f-benzotriazole. If the aromatic ring contains a substituent, the 1- and 3-nitrogen atoms of the triazole are not equivalent, and therefore a 3-//-benzotri-azole derivative can also exist. The equilibrium between the 1 -H and 2-H tautomers of benzotriazoles is strongly on the side of the 1 -H tautomer, in contrast to triazole where the 2-H tautomer is dominant. Tomas et al. (1989) compared experimental data (enthalpies of solution, vaporization, sublimation, and solvation in water, methanol, and dimethylsulfoxide) with the results of ab initio theoretical calculations at the 6-31G level. 

Nitration of a series of mesomeric betaines was extensively studied in connection with their potential use as explosives (Scheme 3). Nitration of l,2,3-triazolo[2,l- ]benzotriazole 74 can be achieved selectively, occurring first at the 7-position which is followed by nitration at the 3- and 5-positions. Thus, nitration with 45% nitric acid gives a mixture of 7-nitro derivative 75 (39%) and dinitro derivative 76 (58%), while 70% nitric acid yields a mixture of 3,7- (52%), 5,7- (23%), and 3,5-dinitro (5%) isomers 76-78. Clean trinitration to 3,5,7-trinitro-l,2,3-triazolo[2,l- ]benzotriazole 79... 

Tetranitro derivative 90 (z-TACOT Section 12.10.15.5) treated with methanolic sodium methoxide at ambient temperature does not lead to simple product of nucleophilic substitution of a nitro group but provides compound 92. Its formation can be rationalized by introduction of the methoxy group into the 1-position, followed by scission of the remote triazole ring of 91 to give the final product. Compound 90 subjected to the vicarious nucleophilic substitution (VNS) conditions using either hydroxylamine or trimethylhydrazinium iodide gives a very insoluble red solid, which was identified as l,3,7,9-tetraamino-2,4,8,10-tetranitrobenzotriazolo[2,l- ]benzotriazole 93 (Scheme 5) <1998JOC3352>. 

The [l,2,3]triazolo[2,l- ]benzotriazole (74 2,3-benzo-l,3a,4,6a-tetraazapentalene) heterocyclic ring system is obtained by an electrophilic attack of singlet nitrene, generated by heating the corresponding nitrophenyl triazole 251 in trialkyl phosphite, on the triazole nitrogen (Equation 39) <1998JOC3352>. 

When treated with DBU at elevated temperature, l-[(benzotriazol-l-yl)methyl -2-aminopyridine salts 741 eliminate rather the N-H proton than the C-H one. Intermediates 742 can be trapped with aromatic aldehydes to create betaines 743. The consecutive cyclocondensation and elimination of benzotriazole results in formation of imidazolo[l,2-rz]pyridines 744 in good yields (Scheme 117) <2000JOC9201>. Aldehydes with enolizable a-protons fail to give bicyclic systems 744, producing corresponding enamines instead. 

Triflate 880 can be formally considered as an ester of the enol form of ketone 879. Treatment with a base causes elimination of the triflate group to afford l-(benzotriazol-l-yl)alkynes 881 (Scheme 144) <20000L3789>. 

To get a complex set of substituents by direct derivatization of benzotriazole is not feasible. In such situations, it is better to have all the substituents in place first and later construct the heterocyclic ring. High reactivity of anilines and their well-developed chemistry makes them good stating materials. In an example shown in Scheme 215, acetanilide 1288 is nitrated to afford nitro derivative 1289 in 73% yield. Catalytic reduction of the nitro group provides methyl 4-acetylamino-3-amino-5-chloro-2-methoxybenzoate 1290 in 96% yield. Nitrosation of compound 1290 in diluted sulfuric acid leads to intermediate 1291, which without separation is heated to be converted to 7-chloro-4-methoxy-l//-benzotriazole-5-carboxylic acid 1292, isolated in 64% yield <2002CPB941>. 

Preparation of 4,5,6,7-tetrabromobenzotriazole and its tetrachloro analog by direct bromination or chlorination of benzotriazole is described in Section 5.01.7. However, other tetra-substituted benzotriazoles have to be constmcted from a suitably substituted benzene ring. Thus, treatment of pentamethylbenzene 1293 with fuming nitric acid in concentrated sulfuric acid provides 3,4,5,6-tetramethyl-l,2-dinitrobenzene 1294 in 66% yield. Using routine procedures, derivative 1294 is reduced with SnCl2 in aqueous HC1, and the obtained diamine 1295 is subsequently treated with NaNOz (in aq. HC1) to provide 4,5,6,7-tetramcthyl-l //-benzotriazole 1296 (Scheme 216) <2004BMC2617>. 

Cancilla, D.A., Baird, J.C., Geis, S.W., and Corsi, S.R. Studies of the environmental fate and effect of aircraft deicing fluids detection of 5-methyl-l//-benzotriazole in the fathead minnow (Pimephales promelad), Environ. Toxicol. Chem., 22(1) 134-140, 2002. 

Similar 1,2,3-diheterocyclizations have been performed by addition of other Af, N- or Al,5-dinucleophiles, such as pyridine-2-thiol, 2-aminopyridine, 2-aminothia-zole, thioisonicotinamide, and l//-benzotriazole, to complexes 6 and 46 giving rise to the formation of the five- and six-membered cyclic alkenyl derivatives 96-100 (Fig. 19) [289, 291,292],... 

Benzotriazoles are neutral acylating agents, successfully used for the preparation of amides, oxamides and hydrazides The acylbenzotriazoles 95a-d are prepared from carboxylic acids 94a-d by reaction with l-methanesulfonyl-l//-benzotriazole (Scheme 51). Reaction of 1-benzoyl-l//-benzotriazole with hydroxylamine hydrochloride in the... 

Die Oxidation von 1-Amino-5,6-dimethy]-l,5-dihydro- mit Blei (IV)-acetat fiihrt unter Abspaltung von Stickstoff zu l, 2-DimethyI-5,6-dehydro-benzimidazol, das mit verschiedenen Dienen abgefangen werden kann655 z.B. ... 

A wide range of 1,2,5-trisubstituted 4-imidazolidinones 4 (Fig. 2)29 was prepared by a synthetic approach based on the formation of a reactive adduct of benzotriazole and aldehyde.30 The /V-[l -(benzotriazol-1 -yljalkyl] derivative from the a-amino group of a resin-bound amino acid underwent spontaneous intermolecular nucleophilic substitution with the... 

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