Tetrahydrofuran, effect

Several alternative methods followed this early work. In one, aromati2ation is effected by treating the ketal of androstadienedione with the radical anion obtained from lithium and diphenyl in refluxing tetrahydrofuran. Diphenylmethane is added to quench the methyllithium produced from the... 

Diborane [19287-45-7] the first hydroborating agent studied, reacts sluggishly with olefins in the gas phase (14,15). In the presence of weak Lewis bases, eg, ethers and sulfides, it undergoes rapid reaction at room temperature or even below 0°C (16—18). The catalytic effect of these compounds on the hydroboration reaction is attributed to the formation of monomeric borane complexes from the borane dimer, eg, borane-tetrahydrofuran [14044-65-6] (1) or borane—dimethyl sulfide [13292-87-0] (2) (19—21). Stronger complexes formed by amines react with olefins at elevated temperatures (22—24). 

Reduction. Heterogeneous catalytic reduction processes provide effective routes for the production of maleic anhydride derivatives such as succinic anhydride [108-30-5] (26), succinates, y-butyrolactone [96-48-0] (27), tetrahydrofuran [109-99-9] (29), and 1,4-butanediol [110-63-4] (28). The technology for production of 1,4-butanediol from maleic anhydride has been reviewed (92,93). 

Goldinonolactone and the tetrahydrofuran moiety of goldinamine were also synthesized from L- and D-mannose, respectively (63). The synthesis of efrotomycin has also been effected (62). 

Alkylation and arylation of organosilanes occur readily with alkyl and aryl alkaU metal compounds. Yields from these reactions are good but are iafluenced by steric requirements on both silane and metal compounds. There is Httie iaductive effect by the organic groups attached to siUcon, as measured by the yield of products (126,127). These reactions proceed more readily ia tetrahydrofuran and ethyl ether than ia ligroin or petroleum ether, where R and are alkyl or aryl and M is Li, Na, or K. 

The column used in the upper chromatogram was 24 cm long, 4.6 mm I.D. the solvent was tetrahydrofuran, the solute benzene and the flow rate 1 ml/min. The column used in the lower chromatogram was 1 m long, 1 mm I.D. using the same solvent and solute but at a mobile phase flow rate of 40 ml/min. It is seen that the reduction in cell volume has a dramatic effect on peak shape. The large 25 pi cell... 

Aromatic steroids are virtually insoluble in liquid ammonia and a cosolvent must be added to solubilize them or reduction will not occur. Ether, ethylene glycol dimethyl ether, dioxane and tetrahydrofuran have been used and, of these, tetrahydrofuran is the preferred solvent. Although dioxane is often a better solvent for steroids at room temperature, it freezes at 12° and its solvent effectiveness in ammonia is diminished. Tetrahydrofuran is infinitely miscible with liquid ammonia, but the addition of lithium to a 1 1 mixture causes the separation of two liquid phases, one blue and one colorless, together with the separation of a lithium-ammonia bronze phase. Thus tetrahydrofuran and lithium depress the solubilities of each other in ammonia. A tetrahydrofuran-ammonia mixture containing much over 50 % of tetrahydrofuran does not become blue when lithium is added. In general, a 1 1 ratio of ammonia to organic solvents represents a reasonable compromise between maximum solubility of steroid and dissolution of the metal with ionization. 

Contrary to Brown s results, a later paper claims that chloral, esters and acid chlorides are readily reduced by diborane in tetrahydrofuran it is suggested that diborane can complex with tetrahydrofuran before effecting reduction. 

Complete exchange of protons in a sterically unhindered position a to a carbonyl group can be achieved by heating a solution of the ketone in O-deuterated solvents in the presence of an acid or base catalyst, the latter being the more effective. The most commonly used solvents are methanol-OD, ethanol-OD, and the aprotic solvent anhydrous tetrahydrofuran or dioxane mixed with deuterium oxide. Under alkaline conditions the exchange rate in 153 2 14,164 stcroids, for example, is usually... 

The isotopic purity of the products from a lithium aluminum deuteride reduction is usually equivalent to that of the reagent. The presence of moisture has little effect on the isotope composition of the products, causing only the decomposition of some of the reagent. For the best results, however, it is advisable to distill the solvent— usually ether, tetrahydrofuran or dioxane depending on the desired reaction temperature—from lithium aluminum hydride directly into the reaction flask. In this manner the reduction of 3-keto-5a-steroids (60), for example, gives the corresponding 3a-di alcohols (61) in 98% isotopic purity. ... 

MonofluoToalkanes and vicinal difluoroalkanes are dehydrofluonnated if strong enough bases are applied [10 12] In 5-fluorononane and fluorocyclodo-decane, elimination by means of sodium methoxide in methanol gives cis- and trans allcenes in respective yields of 8 and 21% and in ratios of 1 2 2 2 4, however, the bulky lithium diisopropyl amide m tetrahydrofuran produces trdns-isomers almost exclusively The strength of the base does not have much effect on the rate of elimination, but the lithium cation causes considerable acceleration [10] (equation 10)... 

There are different reasons to discard a column a column can be damaged by irreversible adsorption of reactive polymer samples. Small amounts of styrene oligomers are known to permanently elute from styrene-divinylbenzene materials with tetrahydrofuran as the eluent, which means a continuous shear degradation of the separation material and consequently a decrease of the packing quality this observation is very important if fractions are collected and used for further analyses, e.g., for the determination of infrared (IR) spectra. One can presume that similar effects are present with other organic materials too. 

Tetrahydrofuran (THE) is known as a liquid that exhibits high affinity toward various adsorbents and therefore effectively suppresses the adsorption of many polymers. Still, THE could not fully suppress adsorption, e.g., of... 

Kinetic investigation of the reaction of cotarnine and a few aromatic aldehydes (iV-methylcotarnine, m-nitrobenzaldehyde) with hydrogen eyanide in anhydrous tetrahydrofuran showed such differences in the kinetic and thermodynamic parameters for cotarnine compared to those for the aldehydes, and also in the effect of catalysts, so that the possibility that cotarnine was reacting in the hypothetical amino-aldehyde form could be completely eliminated. Even if the amino-aldehyde form is present in concentrations under the limit of spectroscopic detection, then it still certainly plays no pfi,rt in the chemical reactions. This is also expected by Kabachnik s conclusions for the reactions of tautomeric systems where the equilibrium is very predominantly on one side. 

The reactivities of compounds of type 6 with aniline in acetone correlate quite well with substituent effects, and autocatalysis is unimportant here. In the less polar tetrahydrofuran, where the hydrochloride is only partly soluble, the reaction shows autocatalysis when aniline and -chloro aniline are reactants but not when the more basic -toluidine is involved. In these cases the solubility of the acidic product may also influence the differential behavior observed. 

D) Preparation of 4-[1 -Methyl-Piperidyl-(4 )]-9,10-Dihydro-4H-Benzol4,5]Cyciohepta[1,2-b] Thiophen-(4)-ol 0.94 g of magnesium filings which have been activated with iodine are covered with a layer of absolute tetrahydrofuran and etched with a few drops of ethylene bromide. A solution of 5.0 g of 1-methyl-4-chloropiperidine in 5 ml of tetrahydrofuran is then added dropwise and boiling then effected for a further hour under reflux. After cooling to room temperature, the solution of 4.5 g of 9,lO-dihydro-4H-benzo[4,5] cyclohepta[1,2-b] thio-phen-(4)-one in 5 ml of tetrahydrofuran is added dropwise. 

Attempts to effect ring expansion of methyl 2-azidobenzoate in the presence of other nucleophiles have failed. Thus, photolysis in tetrahydrofuran solution saturated with hydrogen sulfide, or with ammonia, produced methyl 2-aminobenzoate in 54 and 37 % yield, respectively, as the sole identifiable product.197 Photolysis of phenyl azide in ethanolic phenol gave 2-phenoxy-3//-azepine in poor yield (8 %).203,204 2-Mesityl-3//-azepine (10 %) is the surprising, and only tentatively explained, product from the photolysis of phenyl azide in mcsitylene in the presence of trifluoroacetic acid.179... 

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