Aryl chloroformates Substituents

Solutions of dinitrogen pentoxide in methylene chloride or chloroform have been used for the V-nitration of the sodium salts of some V-alkylsulfamides. " Sulfonamide substrates with both alkyl and aryl substituents are V-nitrated in excellent yields with this reagent. Aromatic ring nitration occurs when aryl substituents are present. 

An important prerequisite in these reactions is the nucleophilicity of the imine nitrogen. Indeed, electron-withdrawing substituents in the aryl ring of (159) retard the reaction with isothiocyanates, whereas such substituents in the R group of the isothiocyanates enhance the reaction. No reaction occurs under the above chosen conditions (reflux in chloroform), when the aryl ring of (159) is replaced by a sulfonyl group <88BSB83>. 

Aryl-l,l-dibromo-2,3-diazabutadienes (223)145 and the JV-amino-amidine (219, R1 = Me, R2 = R3 = Ph) yield 1,3,4-triazolium bromides (220, R1 = Me, R2 = R3 = Ph, R4 = H, R5 = N=CHAr), which with ammonia in chloroform solution give novel derivatives (224) of meso-ionic l,2,4-triazol-3-imines (216). These compounds are of interest in that they belong to a new type of meso-ionic heterocycle in which the exocyclic substituent f (see Table I) is a stabilized carbanionoid residue,... 

Complex 218, in the presence of chlorotrimethylsilane (TMSCl) as a promoter, was found to be the most useful and gave the highest enantioselectivity and best yield in this reaction. Dichloromethane, chloroform, and 1,2-dichloroethane proved to be the best solvents for optimizing enantioselectivity. A limited survey of substituents suggested that this catalyst was not particularly sensitive to the electron demand of the aryl system, although steric effects may be important (Table 37, entry 4). 

The rate of reaction of peracetic acid in acetic acid or perbenzoic acid in chloroform solution is quite sensitive to the number and kind of substituents on the ethylenic carbon atoms. In general, alkyl and aryl groups enhance the reactivity whereas carboxyl, carboalkoxyl, and carbonyl... 

One of the common properties of imidazole N-oxides is their strong association even in dilute solution, and in the solid state such association can mask distinction in the IR between NH and OH bands. Thus IR studies of such compounds in the solid state may give rise to confusing results. Careful UV studies of 1-hydroxybenzimidazoles show that with a variety of substituents (e.g. 6-nitro, 2-alkyl or 2-aryl) the hydroxy form (73) is favoured in organic solvents, and the more polar oxide form (74) in water (there is a mixture of both in aqueous ethanol). With 1-hydroxybenzimidazole the N-methyl model (75) is not sterically hindered, and the value of Kt (74173) = 12 deduced from the pK values of the models (75/76) in water should be much more reliable than that for the hydroxyimidazoles (Scheme 24). In other solvents (benzene, chloroform, acetonitrile, dioxane), UV results show that the OH form (73) predominates in 75% aqueous ethanol Kt=1. 

It was found that just contact with neutral alumina at room temperature in benzene or chloroform suffices to promote quantitative isomerization of compound I to the frani-dihydrofuran derivative II only, with retention of the configuration of the aryl and methyl substituents of cyclopropane I. This highly unusual result was underscored by the formation of both II and III during the parallel thermolysis experiment, a result that follows well established lines. Thus, dihydrofurans II and III are very probably the result of a 1,3-sigmatropic rearrangement formally similar to that described in Problem 14. 

A mixture of the azole (50 mmol), aryl halide (50 mmol), anhydrous potassium carbonate (7g) and copper(II) oxide (0.25 g) in pyridine (10 ml) is refluxed for some hours. The cooled mixture is filtered, extracted with benzene or chloroform, and the combined extracts and filtrate are rotary evaporated to give a residue which is chromatographed on alumina, eluting with benzene or benzene-chloroform. Prepared in this way are the following 1-substitutcd imidazoles (1-substituent, heating time, yield given) o-nitrophenyl, 11 h, 64% m-nitrophenyl, 19.5h, 30% p-nitrophenyl, lOh, 54% o-cyanophenyl, 50h, 43% tw-cyanophenyl, 50.5 h, 13% p-cyanophenyl, 50h, 73% o-acctylphenyl, 7h, 33% m-acetylphenyl, 48h, 68% p-acetylphcnyl, 48h, 82% a-pyridyl, 19h, 37% 3-pyridyl, 24h, 51% y-pyridyl, 12h, 30%. 

Dialkyl, diaryl, unsymmetrical dialkyl, alkyl aryl, and unsymmetrical diaryl telluriums served as the tellurium-containing starting materials (Vol. IX, p. 1075). The reactions with methyl iodide and low molecular mass organic bromides proceed at 20° in organic solvents such as chloroform and methanol or in mixtures of the neat reagents.With aryl telluriums several days are required for completion of the reaction. Diaryl telluriums with ortho-substituents react only with difficulty. Bis[2,4,6-trimethylpheny 1] tellurium did not combine with methyl iodide. The reactions with ethyl iodide and a-bromocarboxylic acids are accelerated by gentle heating. 

Others have reported that there is a definite effect of aryl substituents and that the derivative 39 undergoes cyclization in the presence of dissolved oxygen to yield the hydroxyflavone 40. The cyclization involves the formation of a biradical 41 that cyclizes in the presence of oxygen to yield the hydroxyflavone 42. The cyclization of such chalcones has been known for many years and studied in some detail . Research showed that the derivatives 43 undergo efficient cyclization to 44 (Scheme 4) on irradiation at wavelengths >365 nm in dioxan or ethyl acetate solution . The reaction is solvent-dependent and poorer yields are obtained in benzene or chloroform solution . Further studies demonstrated, for the conversions shown in Scheme 5, that the cyclizations probably arose from a 7171 transition . ... 

AT-Vinyl-substituted isocyanides 57 have been polymerized in the presence of nickel catalysts, yielding poly(vinyl isocyanide)s [79]. The solubility and stability of these polymers very much depends upon the substituent on the vinyl group. Substituted vinyl isocyanide, (CH3)2C=CHNC, afforded polymers that were soluble in chloroform when freshly prepared, although they became insoluble on standing for several days, even at temperatures of -10 °C. The polymerization of vinyl isocyanide proceeded in hydrocarbon solvents, unlike aryl or alkyl isocyanides, which required an alcoholic solvent for efficient polymerization. 

Our first attempt was an enantioselective synthesis of (k)-(+)-carnegine [7,8]. Michael addition of 2-(3,4-dimethoxyphenyl)ethylamine (7) to (R)-(+)-l took place readily at room temperature in chloroform (Scheme 5). Without isolation of any intermediate, the reaction mixture was treated with excess trifluoroacetic acid to effect the cyclization. Depending on the reaction conditions and the aryl substituent of the chiral sulfoxide, different levels of diastereoselectivity were observed. The results are summarized in Table 1. Under proper conditions (TFA, 0°C, 4h), 10b could be obtained in 65% yield as the only isolated product (Scheme 5) (Table 1). 

The sodium salt of 105 with trichloromethyl chloroformate and an alcohol, in sequence, furnished N-3 alkoxycarbonylated 107, through unstable intermediate 106 (Scheme 38). However, an ortho substituent on the C-4 aryl group decreased the yield of the N-3 product (88TL5405). 

NMR data was found to be consistent with the formation of predominantly 1 1 complexes of the receptors and anions. Stability constants were determined by Cram s extraction method in water-saturated chloroform at 30 °C [40]. AfWties for both chloride and bromide anions increased through the series 27a-d, reflecting the increase in acidity of the NH groups due to the electron-withdrawing aryl substituents and the change from urea to thiourea in 27d. In the case of chloride the association constant for the unsubstituted derivative 27a was calculated to be 1.62 x 10 M with the... 

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