Showing papers on "Triazene published in 1999"

Triazenes: A Useful Protecting Strategy for Sensitive Secondary Amines

Abstract: The application of aryl triazene as a protecting group for sensitive secondary amines such as 4-piperidone ( 2) is described. The triazene protected amine is compatible with oxidative and re- ductive conditions as well as with lithiating and alkylating reagents. The free amine is regenerated by treatment with trifluoroacetic acid.

Solid State Photolysis of Triazene 1-Oxides with Naphthols. Synthesis of Azo Dyes

Abstract: Sunlight irradiation of solid mixed crystals of the photolabile triazene 1-oxides and α- or β-naphthol afford azo dyes.

1,3‐Bis(3‐nitrophenyl)triazene

Abstract: The title molecule, C 12 H 9 N 5 O 4 , has trans geometry about the azo linkage. The dihedral angle between the two phenyl rings is 6.2(2)°. The whole molecule is almost planar and the maximum deviation from the mean plane is 0.166 (3) A. The resonance effect in the triazene group which might explain the antitumour activity of some triazene derivatives is discussed. In the crystal structure, while the twofold screw-related molecules are packed in a simple herringbone pattern, the inversion-centre-related molecules form hydrogen-bonded dimers which are held together through π…π interactions along the [010] direction.

Crystal structure and spectroscopic study of bis{1,3-bis[3-(5-amino-1,2,4-triazolyl)]triazenido-N′4,N2,N″4}nickel(II) tetrahydrate

Abstract: The title compound [Ni(batt)2]·4H2O, in which Hbatt is 1,3-bis[3-(5-amino-1,2,4-triazolyl)]triazene, has been prepared and its crystal structure determined by X-ray diffraction methods. The compound crystallizes in the tetragonal space group I4/m (a = 10.5645(8) A, c = 9.1336(6) A, and Z = 2). The Ni(batt)2 molecule has local 4¯ symmetry, but it is located on a crystallographic 4/m site and is disordered over the mirror plane. The ligand batt− is tridentate with nitro-type coordination of the triazenido group and N4 coordination of the two outer triazolyl substituents. The complex has a distorted octahedral geometry with meridional configuration of the two nearly planar batt− ligands. The geometry of the tridentate cavity is examined and a comparison is made with the Ni-terpyridyl system, which shows similar coordination around the nickel center. The FTIR, micro-Raman, and UV-vis spectra are analyzed in relation with the structure.

Modulating effect of new potential antimelanomic agents, spin-labeled triazenes and nitrosoureas on the DOPA-oxidase activity of tyrosinase.

Abstract: The modulating effect of newly synthesized alkylating spin labeled triazene and spin labeled nitrosourea derivatives on the DOPA-oxidase activity of mushroom tyrosinase has been investigated by Burnett's spectrophotometric method (Burnett et al., 1967). All spin labeled triazenes have exhibited activating effect on DOPA-oxidase activity of tyrosinase, whereas clinically used triazene (DTIC), which does not contain nitroxide moiety, have showed inhibiting effect. At the same experimental conditions the spin labeled aminoacid nitrosoureas have showed dual effect - activating, in the beginning of the enzyme reaction and inhibiting later on. It is deduced that the activating effect of the spin labeled compounds is due to the nitroxide moiety and the inhibiting effect of all compounds depends on their half-life time. This study might contribute to make more clear the mechanism of action of the new compounds and on the other hand would come in quite useful as a preliminary prognosis for their antimelanomic activity.

Partial block type polyisocyanate

Abstract: PROBLEM TO BE SOLVED: To obtain a partial block type polyisocyante having scarce amount of a volatile blocking agent, useful for an one component coating agent by bonding a polyisocyanate molecule with an uretedione compound and blocking the terminal isocyanate group with an active hydrogen containing compound. SOLUTION: This polyisocyanate is obtained by an intermolecular bonding of (A) a polyisocyanate having a triazene structure of formula I (R is a residue excluding an aliphatic, a cycloaliphatic diisocyanate group) comprising the aliphatic, the cycloaliphatic diisocyanate and/or a polyisocyanate having a biuret structure of formula II, with uretedione group of (B) compounds having uretedione group of formula III or IV (n>=2; A is a residue excluding hydroxyl groups of polyol) and blocking the terminal isocyanate group of the polyisocyanates by reacting with an active hydrogen containing compound. This partial block type polyisocyante is capable of providing composition with hardly any coloring in baking.

Steric Effects in the Base‐Catalyzed Cyclization of 1‐[2‐(Methoxycarbonyl)phenyl]‐3‐(2‐substituted phenyl)triazenes.

Abstract: Eleven model 1-[2-(methoxycarbonyl)phenyl]-3-(2-substituted phenyl)triazenes were synthesized and their cyclization kinetics examined in aqueous-methanolic buffer solutions (51 wt.% methanol) at various pH values. 3(2-Substituted phenyl)benzo[d][1,2,3]triazin-4(3H)-ones were identified as the cyclization products. The log kobs vs pH plot was linear with a slope of unity. Investigation of the steric and electronic effects of substituents in the ortho position revealed that substituents at the ring which is bonded to the N(3) nitrogen affect the cyclization rate through their steric effect only, while their electronic effects are statistically insignificant. This fact was explained in terms of the ring being tilted from the plane in which the remaining part of the conjugate base anion of the model substrate lies. The assumed and confirmed BAc2 mechanism involving specific base catalysis begins by deprotonation of the triazene giving rise to the conjugate base, continues with formation of a tetrahedral intermediate, and ends with elimination of the methanolate ion. Other mechanisms, such as the elimination-addition mechanism via a ketene intermediate or the mechanism involving general base catalysis, are unlikely.