Reaction refluxing

Since the unpurified toxins show no aldehyde absorption, it was of interest to identify the precursors of helminthosporol and helminthosporal. Thin-layer chromatography of fresh chloroform extracts of the toxin that had been concentrated below 40° indicated several spots (6). One was identified as prehelminthosporol, a hemiacetal (X), from NMR spectra and chemical reactions. Refluxing with triethylamine yielded helminthosporol, identical with Tamura s prod-... 

When R2 substituent is flourocontaining alkyl group, the transformation 17 18 becomes hindered and its proceeding requires some special methods. For example, in [48] Biginelli-like cyclocondensations based on three-component treatment of 3-amino-l,2,4-triazole or 5-aminotetrazole with aldehydes and fluorinated 1,3-dicarbonyl compounds were investigated. It was shown that the reaction can directly lead to dihydroazolopyrimidines 20, but in the most cases intermediate tetrahydroderivatives 19 were obtained (Scheme 10). To carry out dehydration reaction, refluxing of tetrahydroderivatives 19 in toluene in the presence of p-TSA with removal of the liberated water by azeotropic distillation was used. The same situation was observed for the linear reaction proceeding via the formation of unsaturated esters 21. 

A solution of 15 ml. of glacial acetic acid and 30 ml. of water is deoxygenated as described above and then slowly injected with a syringe into the reaction. Refluxing is continued for 6 hours, the flask is cooled, and its contents are poured into a 1-1. separatory funnel along with 200 ml. of water. The solution is extracted four times with 100-ml. portions of ether, and the combined ether extracts are washed successively with 100 ml. of 6N aqueous hydrochloric acid, 100 ml. of water, and 100 ml. of brine. The organic extracts are dried over anhydrous magnesium sulfate, filtered, concentrated with a rotary evaporator, and distilled to yield 13.2-13.8 g. (65-67%) of l-methyl-4,... 

The product from Step 1 (1.22mmol) was dissolved in 70ml dry ethyl alcohol, 3.5ml hydrazine and 7 ml acetic acid added, and the reaction refluxed 2 hours. The mixture was concentrated, the mixture purified by chromatography using neutral alumina and CH2Cl2/methyl alcohol, 98 2, and the product isolated in 66% yield. H NMR and elemental analysis data supplied. 

Triphenylamine (125 g) was dissolved in 5 L ethyl alcohol, HgO (150g) added at 60°C, followed by (100 g), and the reaction refluxed 2 hours. Thereafter, the mixture was hot filtered, the residue washed with acetone, and upon cooling, crystals deposited. The crystals were purified by chromatography using silica gel with toluene and 52 g product isolated. 

Thioglycolic acid (0.1 mol) was added to a solution of NaOH (0.2 mol) dissolved in 200 ml methyl alcohol followed by the addition of 4-fluorobenzyl chloride (0.1 mol) and the reaction refluxed 3 hours. The mixture was cooled to ambient temperature, poured onto crushed ice, neutralized with 200 ml HCl, and the product isolated. 

In the laboratory you will be required to heat chemicals in dissolution of a solid, promotion of reaction (reflux), distillation of pure compounds and mixtures, extraction, coagulation of precipitates, drying solid compounds, etc. Your choice of heat source depends upon several factors ... 

Furanoid glycals utilizing elimination of selenoxides were prepared from unusual substrates, the 4-phenylselenyltetrahydrofurans. These intermediates were obtained with good yields from D-glyceraldehyde (O Scheme 21). Their oxidations have led to selenoxides, however, the elimination reaction required heating. The best yields were noted for reactions refluxed in 1,2-dichloroethane and yields ranged from 62 to 95%. 

Addition reactions. Refluxing with aluminum chloride effects addition of chloro-Idrm to tetrachloroethylene to give Mnsym-heptachloropropane, isolated by cooling,... 

UUmann ether synthesis. The original Ullmann ether synthesis9 involved melting the salt of a phenol with an aryl bromide in the presence of copper metal. Yields are low. Williams et al.10 found that the reaction can be carried out at lower temperatures by using as solvent pyridine, which forms a complex with copper salts (cuprous chloride preferred), which provides catalysis for the reaction reflux temperature is then sufficient. 

The purely thermal reaction (refluxing in xylene) proceeds via consecutive intramolecular sigmatropic [l,5]-hydrogen shifts to give 5-[(2-ethoxycarbonyl)ethyl]uracils. 

A solution of 15 ml. of glacial acetic acid and 30 ml. of water is deoxygenated as described above and then slowly injected with a syringe into the reaction. Refluxing is continued for 6 hours, the flask is cooled, and its contents are poured into a... 

An old but still useful alternative is the Finkelstein reaction,which involves treatment of an alkyl chloride, bromide, mesylate, or tosylate with sodium or potassium iodide to produce alkyl iodides via an Sn2 reaction. Refluxing chloride 159 with sodium iodide, in dry acetone, for example, gave a 95% yield of iodide 160 in Baldwin s synthesis of haliclamines A and Similarly, Shirai and co-workers converted a tosylate... 

In order to prepare the cyclohexenaldehyde 8, 3-hydroxy-2-pyrone 14 and ethyl 4-hydroxy-2-methyl-2-butenoate 15 are subjected to a Diels-Alder reaction in the presence of phenylboronic acid which arranges both reactants to the mixed boro-nate ester 19 as a template to enable a more efficient intramolecular Diels-Alder reaction with optimal control of the regiochemical course of the reaction. Refluxing in benzene affords the tricyclic boronate 20 as primary product. This liberates the intermediate cycloadduct 21 upon transesterification with 2,2-dimethylpropane-l,3-diol which, on its part, relaxes to the lactone 22. Excessive i-butyldimethyl-silyltriflate (TBSTf) in dichloromethane with 2,6-lutidine and 4-7V,A-dimethyl-aminopyridine (DMAP) as acylation catalysts protects both OH goups so that the primary alcohol 23 is obtained by subsequent reduction with lithiumaluminum-hydride in ether. 

Aminoperimidines. Phenyl isothiocyanate added to a soln. of the equimolar amount of 1,8-naphthalenediamine in toluene, and after a few min. of an exothermic reaction refluxed 6 hrs. -> 2-aniIinoperimidine. Y 84%. Also 2-amino-benzimidazoles by a modified procedure (cf. Synth. Meth. 25, 363) s. D. Kiffer, Bl. 2970, 2377. 

Benzylidenebenzylamine mixed with Zerf-butyl hypochlorite in ether, a little methanol added to start the reaction, refluxed 0.5 hr. on a water hath after the... 

Choosing the best solvent for a chemical reaction is an extremely important aspect of organic chemistry. When deciding upon a solvent, chemists consider the solubility of the reactants and products, as well as the mechanism of the reaction and the solvation of intermediates. Further, for reactions that need heating to proceed in a reasonable amount of time, the choice of solvent is guided by its boiling point because this sets the temperature at which the reaction refluxes. Lastly, unless the solvent is intentionally used as a reactant, such as in a solvolysis, it must remain inert. 

Magnesium source for all reactions was MgCl2 + K. AU THF reactions refluxed 3 h prior to fluoride. 

A soln. of benzoylacetone in abs. ether added with stirring to Na-dust in abs. ether, after abatement of the reaction refluxed 0.5 hr., -angelica lactone added, stirred and refluxed 12 hrs. 5,5 -dioxo-2,2 -dimethyl-2,5,2, 3, 4, 5 -hexa-hydro-2,3 -difuryl. Y 88%. K. Syhora, Goll. 26, 2058 (1961). 

A soln. of 3, 4 -dibenzyloxy-2-dibenzylaminopropiophenone in anhydrous ether added at room temp, during 2 hrs. to a suspension of LiAlH4 in ether so as to avoid a too violent reaction, refluxed 4 hrs., and allowed to stand overnight at room temp. -> t/ireo-1-(3,4-dibenzyloxyphenyl)-2-dibenzylaminopropanol (Y 80%) dissolved in 1 1 anhydrous ethanol-methylene chloride, and hydrogenated ca. 30 hrs. with 10%-Pd-on-carbon at room temp, and atomospheric pressure until 5 moles Hg have been absorbed f/ireo-l-(3,4-dihydroxyphenyl)-2-amino-propanol (Y 74-88%). - Direct catalytic reduction of the propiophenone gives only the erj/t/iro-compound, while debenzylation of the alcohol by a variety of other methods was unsuccessful. A. La Manna et al., Farmaco, Ed. Sci. 22, 667 (1967). 

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