Product phase recrystallization

To 10 g of cyclohexane-1,4-oxide is added 40 ml of 12 N hydrochloric acid solution. The solution is mixed thoroughly and allowed to stand at room temperature for 8 days. Water (50 ml) is added to the mixture, the phases are separated, the aqueous phase is extracted with 25 ml of ether, and the ether extract is combined with the organic phase. The ether solution is washed with bicarbonate solution and water and dried over anhydrous sodium sulfate. Ether and unreacted oxide are removed on a rotary evaporator, and the product is recrystallized from petroleum ether, mp 82-83 (yield, 8 g). 

A mixture consisting of 22.7 g potassium o-bromobenzoate, 16.6 g 2,6-dichloro-3-methvlani-line, 12 ml N-ethylmorpholine, 60 ml diethylene glycol dimethyl ether, and 1.0 g anhydrous cupric bromide is heated in a nitrogen atmosphere at 145 C to 155°C for 2 hours. The reaction mixture is diluted with 60 ml diethylene glycol dimethyl ether and acidified with 25 ml concentrated hydrochloric acid. The acidic mixture is diluted with 100 ml of water and the liquid phase decanted from the insoluble oil. The insoluble oil is stirred with methanol and the crystalline N-(2,6-dichloro-3-methylphenyl)anthranilic acid which separates is collected and washed with methanol. The product, after recrystallization from acetone-water mixture melts at 248 C to 250°C. 

A solution of 3.7 g (12 mmol) of the pure (l R)-diastereomer 6 is stirred under nitrogen in 15 mL of iodomethane and 5 mL of dry DMSO for 36 h. The excess iodomethanc is evaporated leaving a viscous red oil which is heated under reflux in 25 mL of 2N KOI for 5 h. After cooling, the amino alcohol is removed from the aqueous phase by extraction with Et20. The alkaline aqueous layer is acidified with 12 N HC1 and extracted with Ei,0. The crude product is recrystallized from benzene/petroleum ether to give enantiomer-ically pure (R)-2-hydroxy-2-phenylpropanoic acid [(-)-(R)-atrolaclic acid] (7) yield 1.4 g (71%) mp U5-116X [x]25 - 38.4 (< = 2.5, EtOH). 

Fig. 11. Schematic representation of dehydration followed by recrystallization of the product phase behind the advancing interface. This model provides an explanation of Smith—Topley behaviour (see text).

Method To a solution of (Et0)2P(0)TeNa (5 mmol) in EtOH (10 mL) is added a solntion of benzene sulphonyl chloride (0.88 g, 5 mmol) in THF (10 mL) under N2. An instantaneous reaction occurs and the colour of the mixture changes from colourless to deep black. After stirring for 20 min, a solution of benzyl chloride (0.64 g, 5 mmol) and catalytic amounts of BzEtjN Cr (0.01 g) in THE (10 mL) is added. The mixture is refluxed for 4 h. After evaporating the solvent nnder reduced pressure, the residue is treated with CHCI3 (50 mL). After filtration, the organic phase is evaporated to dryness. The crnde product is recrystallized from EtOH, giving the pure product (1.93 g (82.4%) m.p. 145-147°C). 

The water phase was extracted with X (,2 x 10 mL). The combined organic layers were washed with Y (2x10 mL) and Z(2 x 10 mL), dried with MgSO,, and evaporated in vacuo. The crude product was recrystallized from ethanol at -10 °C and further purified using column chromatography. 

Materials. CEVE and 4-nitrophenyl vinyl ether (VNP) were synthesized and purified as reported earlier (12,13), respectively. 2-(4-Nitrophenoxy)ethyl vinyl ether (NPVE) (m.p. 72-73°C) was prepared by reacting of potassium 4-nitrophenoxide (PNP) (142 g 0.8 mol) and CVE (842 g 7.9 mol) using tetra-n-butylammonium bromide (TBAB) (4.0 g 12 mmol) as a phase transfer catalyst at the boiling temperature of CVE for 12 h. The potassium chloride produced was filtered off, the filtrate washed with water, excess CVE evaporated, and then the crude product was recrystallized twice from n-hexane. (Yield 61.7%. IR (KBr) 1630 (C=C), 1520 (-N02), and 1340 cm-1 (-N02).) Elemental analysis on the product provided the following data Calculated for C10HnNO4 C, 57.40%, H, 5.30%, N, 6.69%. Found C, 57.49%, H, 5.3%, N, 6.72%. 

Schmidt et al. found that a distinct product phase appeared at less than 10% conversion in some cases (indicating heterogeneous reaction), while in others none was evident at greater than 70% conversion [63]. Certain derivatives, (3-truxinic acids in particular, were formed in a modification different from that into which they could be recrystallized. Schmidt interpreted these results in terms of a phase separation of the forming product which occurs when it reaches a limiting solubility in the lattice of the reactant. He further pointed out that recrystallization may be necessary to improve yields in the dimerization of 0-cinnamic acids in certain instances where monomer molecules may be stranded in nonreactive sites such as M2.. M.. M2 (Section IV.B.5.). 5-Bromo-2-hydroxy-cinnamic acid is an example of a case where there is no evidence for phase separation and reaction is found to be slow and proceed in low yield [63,108]. 

In nonreactive molten salts, on the other hand, flux components are not incorporated into the product phase. Here, the molten salt acts more in the classical sense as a reagent to promote the reaction at a lower temperature than would be required by the ceramic, or direct, route (Section 5.2). This is accomplished by two attributes of molten salts an acid-base equilibrium that enables the general dissolution-recrystallization of metal oxides and a highly electropositive (oxidizing) environment that stabilizes the highest oxidation state of many transition metals (Gopalakrishnan, 1995), which can lead to mixed valency. A plethora of complex transition metal oxides have been synthesized in nonreactive molten alkali metal hydroxides, carbonates, and hypochlorites. Examples of such molten salt routes to mixed transition metal oxides include (Rao and Raveau, 1998) ... 

Dimethyl-2-oxo-l-butyl 4-Methoxyphenyl Tellurium Dichloride1 A suspension of 1.02 g (3.0 mmol) of 4-methoxyphenyl tellurium trichloride in 10 m/ benzene is mixed with 0.516 g (3.0 mmol) 3,3-dimethyl-2-trimethylsiloxybut-1 -ene. The mixture is refluxed for 10 h, then treated with 100 ml methanol/water (1 1), and extracted with chloroform. The organic phase is separated, dried with anhydrous magnesium sulfate, filtered, and the filtrate evaporated. The residue is chromatographed on silica gel with chloroform as the mobile phase. The product is recrystallized from chloroform/petroleum ether (30-60°) yield 80% m.p. 90-92°. 

Phenyl-l,3-benzotellurazole 5.0 g (20 mmol) of 2-aminophenyl ethyl tellurium and 5 ml of triethylamine are dissolved in 20 ml of dichloromethane and the solution is cooled in an ice/water bath. 3.5 g (25 mmol) of benzoyl chloride dissolved in 10 m/ of dichloromethane arc added dropwise to the cooled solution of the tellurium compound and the mixture is stirred for 2 h. The crude 2-(N-benzoylamino)-phenyl ethyl tellurium is isolated, placed in 20 ml of phosphoryl chloride, and the mixture is heated under reflux for 3 h. After being cooled in an ice/water bath, the mixture is carefully hydrolyzed with an aqueous base and treated with sodium disulfite. The basic mixture is extracted with dichloromethane, and the extract is dried and concentrated under vacuum. The residue is chromatographed on a column of silica gel with hexane as the mobile phase and the product is recrystallized from hexane yield 0.9 g (15%) m.p. 118-120°. Similarly prepared were ... 

Bts 2,4-dinitrophenyl]-6,7-butano-7elv-(l,2,3]telluradiazolo(2,3-6](l,2,3]telluradiazolez 24.4 g (50 mmol) of the 2,4-dinitrophenylhydrazone of 1,3-cycloheptanedionc and 8.8 g (55 mmol) of tellurium dioxide are added to a mixture of 180 ml xylene and 20 ml amyl alcohol. The mixture is heated under reflux for 24 h. The solvents are then evaporated under vacuum, the residue is dissolved in a small amount of benzene, and the solution is chromatographed on a column of alumina with benzene as the mobile phase. The product is recrystallized from benzene yield 0.6 g (2%) m.p. 251°. 

Mcrcury(II) acetate (6.37 g, 20 mmol) was added during 10 min to a stirred solution of a prop-2-yn-l -ol (20 mmol) and an aromatic 1,2-diamine (20 mmol) in THF (80 mL). After the mixture had been stirred for 14 h at rt or 60 °C the precipitated Hg (> 90%) was filtered off and the liquid phase was treated with 3 M aq KOH (15 mL) and extracted with Et O (3 x 15 ml). The ethereal layer was dried (Na.SO ), the volatile components were evaporated under reduced pressure, and the crude product was recrystallized from EtOH. In the case of 22b, the crude product was distilled in vacuo. 

Bis[methoxymethyl]-2,S-diphcnylte1lurophene 430 mg (1 mmol) of 3,4-bis[chloromethyl]-2,5-diphenyl-tellurophene are added to a solution of sodium methoxide prepared from 40 ml of absolute methanol and 200 mg (8.7 mmol) of sodium and the mixture is heated under reflux for 10 h. The mixture is then allowed to cool to 20°, poured into water, and extracted several times with diethyl ether. The combined extracts are dried with anhydrous sodium sulfate, filtered, and the filtrate is evaporated. The residue is chromatographed on silica gel with benzene as the mobile phase to give the product as a light yellow oil yield 350 mg (83%). l,3-Diphenyl-4//,6//-selenophene[3,4-c]tellurophene A solution of disodium selenide, prepared from 1.58 g (20 mmol) of selenium and 0.92 g (40 mmol) of sodium in liquid ammonia, in absolute methanol is saturated with nitrogen. 1.28 g (3 mmol) of 3,4-bis[chloromethyl]-2,5-diphenyltellurophene are added and the mixture is refluxed under nitrogen for 15 h. The mixture is then filtered, the filter cake is dissolved in chloroform in the presence of activated charcoal, filtered, and the product is recrystallized from chloroform/methanol yield 0.79 g (60%) m.p. 220°... 

Telluropheno[2,3-A]quinoline 1.13 g (4 mmol) of 2,3-dihydrotelluropheno[2,3-6]quinoline arc dissolved in carbon tetrachloride, and the solution is cooled and stirred in an ice bath while a solution of 1.02 g (4 mmol) of iodine in 20 m/ of carbon tetrachloride is added dropwise over 1 h. Cooling and stirring are continued for 1 h, a solution of 3 m/ of DBU in 50 ml of dry chloroform is then added to the reaction mixture until it becomes colorless, and stirring is continued for a further 15 min. The mixture is then extracted with water, the organic phase is separated, dried, filtered, and evaporated. The residue is chromatographed on a column of basic alumina with benzene/petroleum ether as the mobile phase and the product is recrystallized from benzene/petroleum ether (b.p. 60 80°) yield 0.3 g (30%) m.p. 56-58°. 

---