Benzotriazol l-oxide

Nitro-azobenzole werden primar zu den analogen Hydrazobenzolen reduziert. In Ammoniakpuffer-Losung bildet sich an Quecksilber bei —0,5 bis —0,65 V quantitativ das 2-Aryl-2H-benzotriazol-l-oxid. Bei —1,0 bis —1,4 V entsteht ebenfalls quantitativ das... 

Figure 10 The N signal assignments of 1-benzoyloxybenzotriazoles and benzotriazole-l-oxides.

Condensation of A -acylglycines with carbonyl compounds, the Erlenmeyer synthesis, continues to be exploited to prepare of a wide variety of unsaturated-5(47/)-oxazolones. The reaction is performed in the presence of a cyclodehydrating agent and recently bismuth(lll) acetate has been evaluated in this capacity. Alternatively, unsaturated 5(47/)-oxazolones can be obtained from hippuric acid and a carbonyl compound or from the appropriate dehydroamino acid derivative using 3-(aIkoxycarbonyl)benzotriazole-l-oxides as the cyclodehydrating agent. 

Beim Bestrahlen von l-(2-Nitro-pheny])- bzw. l-(2,4-Dinitro-phenyl)-lH-pyrazolen(253,7 nm, 300nm und 355 nm) werden 2-(2-Acyl-ethenyl)-benzotriazol-l-oxide als (.E/Z)-Isome-ren-Gemische gebildet z. B2363 ... 

Isomer Schmp. 123-124° 2- (l-Methyl-3-oxo-1 -butenyl)-2H-benzotriazol-l-oxid... 

The reduction of several indolo[2,3-a]quinolizidines by BY gave novel products resulting from reduction of the indole double bond, cleavage of the C-D ring junction, or reduction of a lactame to a carbinol amine [371]. The known reduction of aromatic nitro compounds has been used as a key step in the synthesis of 2-aryl-2/f-benzotriazoles. Thus, treatment of the o-nitrophenylazo dye 342 gave the 2-aryl-2/7-benzotriazole-l-oxides 343 in good yields [513]. 

A new type of rearrangement has been reported for certain l-(o-nitrophenyl)pyrazoles (169), giving cis- and trans-benzotriazole 1-oxides (170 Scheme 12) (73TL891). The reaction was rationalized in terms of an intermediate azo compound (171 formed in turn either from the diradical species (172) or from the intramolecular 1,4-adduct (173). Subsequently... 

Adamantylation of benzotriazole represents a special case because direct substitution in adamantanyl halides by an Sn2 mechanism is impossible, and an SnI mechanism is improbable. In this case, reactive cation 91 is generated by oxidative cleavage of the C-I bond in 1-iodoadamantane 90. Benzotriazole added to the reaction mixture binds cations 91 to afford a mixture of benzotriazol-l-yl 92 and -2-yl 93 derivatives in a ratio of 26 74 and the total yield of 67% (Scheme 5) <2001RJ01762>. 

Perhaps due to oxidizing quinoid type electronic structure of benzotriazol-2-yl derivatives, some of their properties are completely different from those of isomeric benzotriazol-l-yl derivatives. Thus, anions derived from 2-alkylben-zotriazoles 388 are rapidly converted to appropriate radicals that undergo coupling to form dimers as mixtures of racemic 289 and meso 390 forms <1996LA745>. When the reaction mixture is kept for an extended period of time at —78 °C, (Z)- 391 and (E)- 392 alkenes are formed. When benzophenone is added to the reaction mixture, alcohols 387 are obtained in good yields however, benzaldehyde does not react under these conditions (Scheme 63). 

Die Verbindungen sind auch direkt aus 4,6-Dinitro-benzofurazan-l-oxid mit N-Formyl-anili-nen in alkalischer Losung zuganglich. Benzofurazan-l-oxid selbst liefert keine 4-Anilino-benzo-furazane, sondern man erhalt Benzotriazol-1-oxide78. 

Whereas in the gas phase and in nonpolar solvents sueh as tetraehloromethane and benzene, the 2-azidothiazole (38a) is the more stable isomer, in polar solvents such as dimethyl sulfoxide and hexamethylphosphorie triamide the bieyelie valenee isomer (38b) is the dominant speeies [100]. This result is in line with the faet that the dipole moment of phenyl azide g = 5.2 10 Cm) is smaller than that of cyclie 1,2,3-benzotriazole (// = 13.7 10 Cm). Similar results have been obtained for the valenee isomers of 3-azidopyrazine-l-oxide [204]. 

BDMP 5-(l//-benzotriazol-l-yl)-3,4-dihydro-l-methyl 2//-pyrrolium hexachloroantimonate N-oxide BDP benzotriazol-l-yl diethyl phosphate... 

This reagent, benzotriazol-l-yl-oxytripyrrolidinophosphonium hexafluorophosphate (14, PyBOP)P l (Scheme 4), was designed in order to avoid the formation of toxic HMPA during acylation. As with BOP, it is assumed that the first step is the carboxylic acid activation which involves formation of an acyloxyphosphonium salt.P This initial salt is then attacked by the benzotriazolyloxy anion to form the benzotriazolyl active ester which then reacts with the amino component. PyBOP can easily replace the BOP reagent and is especially suitable for solid-phase peptide synthesis. It is soluble in a wide range of solvents such as DMF, di-chloromethane, THF, and NMP. PyBOP is more useful in peptide synthesis on solid support than in solution. The byproduct, tris(pyrrolidino)phosphine oxide is partially water-soluble and is easily removed by washing. PyBOP is used under the same experimental conditions as BOP. Note that PyBOP is a white, crystalline and non-hygroscopic solid. It can be kept as a solid, but solutions of PyBOP cannot be stored for more than 24 hours. 

These derivatives were described as uronium salts by analogy with phosphonium salts, but X-ray analysis demonstrated that HBTU, HATU, and HAPyU crystahize as aminium salts (guanidinium A-oxides) rather than uronium salts.t NMR studies of HAPyU in solution show the same structure as that observed in the crystahine form.P This discovery changes the nomenclature of these compounds, but their acronyms are unchanged, and they are described in the literature as uronium or aminium salts without discrimination. HBTU should be reformulated as A-[(l//-benzotriazol-l-yl)(dimethylamino)methylene]-A-methyl-methanaminium hexafluorophosphate A-oxide, HATU as A-[(dimethylamino)(l//-l,2,3-triazolo[4,5-b]pyridin-l-yl)methylene]-A-methylmethanaminium hexafluorophosphate A-oxide, and HAPyU as 0-(7-azabenzotriazol-l-yl)-A,A,A, A -bis(tetramethylene)uronium hexafluorophosphate. 

Coupling with Et2N using TBTU [2-(lH-benzotriazol-l-yl)-l,l,3,3-tetramethyluronium tetrafluoroborate], removal of the benzyl group and oxidation with the Dess-Martin periodinane... 

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