Reactions of 2-hydroxymethylphenols with Lawesson's reagent

On interacting 2-hydroxymethylphenols and the Lawesson's reagent 2-(4-methoxyphenyl)-4H-1,3,2-benzoxathiaphosphinine-2-sulfides were obtained. The formation of highly reactive o-quinone methides as intermediates is proposed.     

Reactions of p-quinone monoimines with lawesson reagent and phosphorus pentasulfide

2, 4-Bis-(4-methoxyphenyl)-1, 3, 2, 4-dithiadiphosphetane-2, 4-disulfide [Lawesson reagent (LR)] 1 reacts with p-quinone monoimine- 2a to give the novel benzo-1,3,2-oxathiaphosphol-5-(methanesulfonamido)-2-(4-methoxyphenyl)-2-sulfide 4 . On the other hand, the reaction of 2b and 3 with LR 1 leads to the formation of the benzo- and the naphtho-1,3,2-dithiaphosphol-5 -(benzenesulfonamido)- 2- (4-methoxyphenyl) -2-sulfide 5 , 6 . Thiation of 2a , 2b , and 3 with P₄S₁₀ yields phenoxathiin derivatives 8a , 8b , and 9 , respectively. The identity of the new products is established from analytical and spectroscopic evidence.     

Reactions of a phosphavinyl Grignard reagent with main group mono-halide compounds

The reactions of a phosphavinyl Grignard reagent, [CyPC(Bu^t)MgCl(OEt₂)] Cy=cyclohexyl, with a variety of main group 13, 14 and 16 mono-halide compounds have been investigated. When the Grignard reagent is reacted with bromocatecholborane the terminal phosphavinyl complex, [(C₆H₄O₂)B{C(Bu^t)PCy}], is formed. Related terminal phosphavinyl tin and gallium complexes, [R₃Sn{C(Bu^t)PCy}], R=Me or Buⁿ and [IGa{C(Bu^t)PCy}₂], have been prepared by similar routes. The reaction of the Grignard reagent with PhSeCl has afforded a new λ⁵,λ⁵-diphosphete, [{(Bu^t)CP(Cy)(SePh)}₂], the mechanism of formation of which is discussed. The preparation of a phosphavinyl selenium compound, [(C₈H₄O₂N)PC(Bu^t)(SePh)], is also described. All compounds have been spectroscopically characterised and several have been crystallographically authenticated.     

Mechanisms of antioxidant action: the role of 2-hydroxybenzophenones in photo-oxidizing media

A study of the photo-stability of 2-hydroxy-4-octyloxybenzophenone (HOBP) in the presence of possible photo-sensitizers present in polymers shows that this u.v. stabilizer is readily destroyed by them in the presence of light. HOBP is destroyed by carbonyl compounds and therefore appears to interfere with their photolysis at least partly by a sacrificial quenching process.     

Ultraviolet absorbers for retarding wool photo-degradation: Sulphonated long-chain substituted 2-hydroxybenzophenones

A series of sulphonated 2-hydroxybenzophenones containing 4-alkyloxy substituents of varying chain length has been synthesised and applied to wool fabrics. The higher members of the series, especially those with n-hexadecyloxy or n-octadecyloxy substituents, protect wool from photo-yellowing and photo-tendering more effectively than do the lower members. The higher members have the additional advantages that they are absorbed almost quantitatively during application and are not removed during laundering. The greater level of photo-protection provided by the higher members is unlikely to be due to their preferential location near the fibre surface, because redistribution of the absorber uniformly throughout the fibre does not reduce the level of protection. Other reasons for the observed differences in photo-protective behaviour are discussed.     

Domino reaction to functionalized 2-hydroxybenzophenones from electron-deficient chromones and 1,3-dicarbonyl compounds

A base-promoted one-pot tandem reaction sequence has been developed to transform electron-deficient chromone-fused dienes 1 and 1,3-dicarbonyl compounds 2 to functionalized 2-hydroxybenzophenones 3 under mild conditions. This domino process, which involves multiple reactions, including Michael addition/cyclization/elimination, serves as an efficient, economic, and eco-friendly method for the construction of diversified 2-hydroxybenzophenone scaffolds without a transition-metal catalyst and inert atmosphere.     

Reactions of 2-hydroxybenzonitrile with isocyanates

Triethylamine catalyzes the reaction of 2-hydroxybenzonitrile ( 1 ) with aryl isocyanates to form the corresponding carbamates 2a-c , as well as the cyclization of the latter compounds to either 4[N-(N-arylcarbamoyl)-imino]-3-aryl-2H-1,3-benzoxazin-2-ones 4a-c , or 4-arylamino-2H-1,3-benzoxazin-2-ones 7a-c , depending on the reaction temperature. Under analogous conditions, the carbamates obtained from 1 and 2-chloroethyl isocyanate, 3-chloropropyl isocyanate and ethyl isocyanatoacetate undergo a double cyclization yielding imidazo- and pyrimido[1,2-c|1,3]benzoxazinones 13a,b,17 . Upon heating in phenyl ether, compounds 7a-c , rearrange to 2-(2-hydroxyphenyl)-4(3H)-quinazolinones 10a-c .     

Reactions of 2-arylhydrazonoacetamidoximes with orthoesters

The reactions of 2-arylhydrazono-2-carbamoylacetamidoximes with orthoesters afford either 3-arylhydrazono-1,2,4-oxadiazoles or 1,2,3-triazoles, depending on the reactant structure.     

Reactions in water: alkyl nitrile coupling reactions using Fenton's reagent

The coupling reaction of water-soluble alkyl nitriles using Fenton's reagent (Fe(II) and H2O2) is described. The best metal for the reaction is iron(II), and the greatest yields are obtained when the concentration of the metal is kept low. Hydrogen-atom abstraction is selective, preferentially producing the radical alpha to the nitrile. In order to increase the production of dinitrile, in situ reduction of iron(III) to iron(II), using a variety of reducing agents, was investigated.     

Reactions of 2-amino- and 2-hydrazinobenzimidazoles with 2-acyldimedones

The reaction of 2 formyldimedone with 2-amino- and 2-hydrazinobenzimidazoles at 20°C in ethanol gave 2-(2-benzimidazolyl)aminomethylene- and 2-[2-(2-benzimidazolyl)hydrazinomethylene]-5,5-dimethylcylohex-anediones, while this reaction carried out in ethanol at reflux in the presence of acid gave 2,2-dimethyl-4-oxo 1, 2, 3, 4-tetrahydroquinazolino(1, 2-a]benzimidazole and 1-(2-benzimidazolyl)-6, 6-dimethyl-4-oxo-4, S, 6, 7-tetrahydroindazole, respectively.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 247–252, February, 1996.     

Ultraviolet absorbers for retarding wool photo-degradation: Sulphonated 2-hydroxybenzophenones and 2,2′-dihydroxybenzophenones

Nineteen sulphonated 2-hydroxybenzophenones and three sulphonated 2,2′-dihydroxybenzophenones have been prepared and compared with a commercially available member of each class of uv absorber as photo-protective agents for wool. Treated fabrics were exposed to Philips ML G/74 lamps and the extent of photo-tendering was assessed by measuring breaking loads and tear strengths. In general, 2-hydroxybenzophenones with 3-alkyl substituents provide better protection against photo-tendering than absorbers lacking 3-alkyl substituents. 2,2′-Dihydroxybenzophenones are more effective than 2-hydroxybenzophenones.

On the basis of effectiveness and ease of synthesis, 2,2′-dihydroxy-4,4′-bis-w-sulphobutyloxybenzophenone (VIIb) shows most promise as a photo-protective agent. At the 5% level of application it trebles the lifetime of wool fabric during exposure to sunlight through window glass. It also retards the photo-tendering and fading of wool fabrics containing either a red or a blue milling acid dye.     

Reactions of 2-aminothiophenol with pyridineand imidazolecarboxaldehydes

Russian Chemical Bulletin - Reflux of imidazole-2-carboxaldehyde, 1-methylimidazole-2-carboxaldehyde, imidazole4-carboxaldehyde, or 5-bromopyridine-2-carboxaldehyde with 2-aminothiophenol in...     

Reactions of fluorinated silanes with 2-nitrocinnamates

The interaction of 2-nitrocinnamates with silicon reagents Me₃SiR_f (R_f = CF₃, C₂F₅, and C₆F₅) promoted either by sodium acetate in DMF or by tetrabutylammonium acetate in dichloromethane has been described. The reactions proceed as conjugate addition of fluorinated carbanion at the CC bond and afford 3-aryl-2-nitrobutanoates bearing a fluorinated substituent in good yields as diastereomeric mixtures in ratio from 1:1 to 1.6:1.     

Reactions of 2-arylaminobenzo-thiazoles with methyl acrylate

Addition of 2-arylaminobenzothiazoles to the C=C bond of methyl acrylate gives a mixture of isomeric 2-arylimino-3-(β-carbomethoxyethyl)benzothiazolines and 2-[N-aryl-N-(β-carbomethoxyethyl)amino]-benzothiazoles. Their thermal stability was studied, HPLC analysis was used to follow the dynamics of the accumulation of the compounds formed in the reaction mixtures. Institute for the Chemistry of Plant Materials, Uzbekistan Republic Academy of Sciences, Taskhkent 700170. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1428–1431, October, 1999.     

Reactions of thiolate anions with 2-substituted-2-nitropropanes

Thiolates undergo substitution reactions with 2-substituted-2-nitropropanes by an S_RN1 mechanism or are oxidised to disulphides by an ionic mechanism.