Dioxane as solvent

Initially, 4-methylthiazole (7), R, = Me, Rj = H, was obtained in low yield (<40%) from chloroacetone (102,127). Kurkjy and Brown (364) using bromoacetone with dioxane as solvent increased the yield to 73%, whereas it only yields 39% in benzene (426). Kurkjy and Brown s method was extended later to 4-alkylthiazoles by Metzger and Carrega (455) with 75 to 90% yields. 4-Vinyl- and 4-isopropenylthiazoles (629), 4-adamanthylthiazole and derivatives (705), 4-carboranylmethylthiazole (706), 4,5-dialkylthiazoles (156, 220, 426, 703, 810), 4,5-... 

The mechanistic details of photo-induced grafting of styrene onto cellulose in the presence of mineral acids with methanol and dioxane as solvents was investigated... 

Morrison and Migdalof (Ref 14) irradiated o-nitrotoluene and p-nitrotoluene with a Pyrex-filtered mercury lamp using D20 and p-dioxane as solvents. C-D bonds formed with o-nitrotoluene, with no C-D formation for p-nitro-toluene - ... 

We begin with studies of the pKa values of substituted phenylmercapto-, phenylsulfinyl-and phenylsulfonyl-acetic acids. Pasto and Kent136 found that phenylsulfinylacetic acid was a weaker acid than phenylsulfonylacetic acid in water, the pKa values at 25 °C being 2.732 and 2.513 respectively. However, in aqueous ethanol or aqueous dioxan as solvent... 

This acylation reaction is performed in the presence of triethylamine using DMF or dioxane as solvent [83]. 

The oxidation of sulphoxides with peracid resins occurs rapidly and quantitatively at 20°C using dioxane as solvent . Vanadium(V), generated on a polymer support by treatment of vanadium(IV) with a hydroperoxide (equation 49) may be used to oxidize successfully sulphoxides to sulphones in very good yields . ... 

A more commonly used catalyst for hydrogenation has been 5% Pd/C in either ethanol or dioxane as solvent. Reduction of the carboxylate... 

It should be noted at this point that primary and secondary reaction products can be distinguished not only by kinetic data (13) but also by suppression of the secondary reactions. E.g substitution of 2,2,2-trifluoroethanol for p-dioxane as solvent for HCoCCO) suppresses homologation and methane formation addition of a phosphine to give the less acidic catalyst HCo(CO)3PR3 has the same effect, as has the substitution of the less acidic catalyst HMn(CO)5. 

Treatment of l-methyltetrazolo[5,l-tf]isoindolium perchlorate 49 with acyl chlorides and triethylamine in dioxane as solvent affords a mixture of the 5-acyl-l-methyltetrazolo[5,l-tf]isoindoles 50 and the monomethine cyanine dye 51 (Equation 2) <2004T195>. 

Data are for 25 °C and 60% dioxan as solvent (Kice and Liu, 1979) b Rate constants are total rate of attack of nucleophile on PhS(0)SPh. Preference for site of attack (or S=0) shown in parentheses where known... 

The resolution was then based on the enzymatic propanolysis of this derivative in dioxane as solvent. Lip Novozyme 435 selectively cleaves the L-form of the oxazolone producing an L-enriched (81-87% ee) 2-acetamido-3-(heteroaryl)propionic acid propyl ester, the dynamic aspect of the process being based on the continual racemization of the residual oxazolone. The propyl group was then removed with alkali and a second selective enzymatic step to remove the acetyl protecting group with Fluka Acylase 1 produced the L-amino acid at better than 99% ee (Scheme 13). 

In this example the solvent - a fluorinated alcohol - forms higher order aggregates and activates for the epoxidation of electron rich olefins. HFIP accelerates this oxidation reaction up to 100,000-fold (relative to that in 1,4-dioxane as solvent). Which hydrogen bond network involving olefin, and fluorinated alcohol gives rise to such spectacular accelerations ... 

The experiment with 1,4-dioxane as solvent was characterized by poor solubility of GO and KOH into the solvent, hence water was added to the initial mixture. The absence of the hydroxyl functionality in the solvent significantly decreased the system s reactivity. The overall conversion and reactivity in this medium was intermediate, but interesting is that (a) no LA was formed and (b) the selectivity toward EG was substantially higher than in any other solvents. 

Most work has been done by the same group of workers,360 363, 364, 367 433, 435,440 and practically all examples are from type B systems except for a study of the annular tautomerism (Section IV,A1) of 4-methyl-6-phenylpyrazolo[3,4-d]-u-triazole (90),367 a type A system. Values shown here are expressed in Debyes (D), using dioxane as solvent. 

If methanol, as a less basic alcohol than 1-propanol, is used in dioxan as solvent, then, contrary to the model giving rise to eqn. (26), the ester is adsorbed (protonated) and alcohol reacts directly from the liquid phase, and thus... 

The compound was obtained in 90% yield by coupling o-Abz with HOBt using DCC in dioxane as solvent (0.5 M) with addition of pyridine (2 equiv), and was recrystallized (iPrOH) mp 134.5-135.5 °C. 

As mentioned above in connection with the acetic acid synthesis, iridium complexes catalyze the water-gas shift reaction (equation 70). From IrCl3-3H20 and sulfonated derivatives of bipy and phen, water-soluble catalysts were obtained.444 Using dioxane as solvent, complexes of the type [Ir(cod)L2]+ (L= PMePh2, PPh3), [Ir(cod)L ]+ (L = diphos, phen, 4,7-Me2-phen, 4,7-Ph2-phen, 3,4,7,8-Me4-phen) and [Ir(cod)X] (X = 4,7-diphenylphenanthroline disulfonate) also catalyzed the reaction, with the anionic species being most active.470 The mechanism was thought... 

In 1959-1960, Reutov et al.1 reported that the electrophilic substitution of a-carbethoxybenzylmercuric bromide by mercuric bromide, labelled with 203Hg, followed second-order kinetics, first-order in each reactant, in 70% aqueous dioxan as solvent. The substitution may be represented as... 

Polar solvents facilitate these additions. The addition of acrylonitrile or ethyl acrylate to 1-pyrrolidinocyclohexene shows marked solvent dependence. In dioxane as solvent, an 80% yield of monocyano- or... 

In tetrahydrofuran as the reaction medium the yields are only half of those obtained with dioxane as solvent. The cyclic tellurium compounds are not very sensitive to air and light, but decompose under acidic conditions with deposition of tellurium1. 

Determination of Initial Rates of Peroxidase Catalysis in Organic Media. As a typical oxidation reaction, the following example with dioxane as solvent is discussed. 

Some further details of the mechanisms of photo-equilibration and fragmentation of cholest-5-en-3/3-o and -4-en-3/3-ol have been elucidated by the use of a variety of aromatic compounds as sensitizers.249 Reaction is favoured by use of phenolic compounds which can associate with the reactant. Fragmentation, which leads via the unsaturated aldehyde (314) to the oxetan (315), is particularly favoured by the presence of phenol, with dioxan as solvent, and is most efficient with the 4-en-3/3-oI. 

In 1996, Wolfe and Buchwald reported that the (o-tolljP/Pd catalyst system effectively couples secondary amines with aryl iodides, Eq. (37) [67]. This protocol allowed for the successful reaction of both cychc and acyclic secondary amines the use of dioxane as solvent was key to the success of these reactions. Similarly, Zhao and co-workers reported the couphng of aryl iodides and piperazines mediated by the (o-tolljP/Pd catalyst [25b]. 

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