Tetrahydrofuran decomposition

Henry TB, Menn FM, Fleming JT et al. (2007) Attributing effects of aqueous C60 nano-aggregates to tetrahydrofuran decomposition products in larval zebrafish by assessment of gene expression. Environ. Health Perspect. 115 1059-1065. 

Dianion formation from 2-methyl-2-propen-l-ol seems to be highly dependent on reaction conditions. Silylation of the dianion generated using a previously reported method was unsuccessful in our hands. The procedure described here for the metalation of the allylic alcohol is a modification of the one reported for formation of the dianion of 3-methyl-3-buten-l-ol The critical variant appears to be the polarity of the reaction medium. In solvents such as ether and hexane, substantial amounts (15-50%) of the vinyl-silane 3 are observed. Very poor yields of the desired product were obtained in dirnethoxyethane and hexamethylphosphoric triamide, presumably because of the decomposition of these solvents under these conditions. Empirically, the optimal solvent seems to be a mixture of ether and tetrahydrofuran in a ratio (v/v) varying from 1.4 to 2.2 in this case 3 becomes a very minor component. 

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. ... 

Changing the eluent in a ready-made column is sometimes combined with a loss of packing quality. The manufacturers try to hold the number of specified solvents for one packing type as low as possible, but some eluents have to be nominated at order time. Any replacement has to be performed strictly according to the instructions of the manufacturers. Not every eluent is suitable for the long-term storage of a used column (e.g., reactive decomposition products of tetrahydrofuran or corrosion by some aqueous buffers) and have to be replaced. 

The reaction of enamines derived from cyclohexanone with dichlorocarbene to give the 1 1 adducts is now well established (137-139). The morpholine enamine (113) reacted with dichlorocarbene at —10 to —20° in tetrahydrofuran to give the stable crystalline adduct (201). Thermal decomposition followed by an aqueous work-up gave an a,)3-unsaturated ketone identified as 2-chloromethylene-cyclohexan-l-one (202) (139). 

To this acid was then added 1 g of 4-ethyl-2,3-dioxo-1-piperazinocarbonyl chloride (from the reaction of N-ethylethylenediamine and diethyl oxalate to give 2,3-dioxo-4-ethyl-piperazine which Is then reacted with phosgene) and the resulting mixture was reacted at 15°C to 20°C for 2 hours. After the reaction, a deposited triethylamine hydrochloride was separated by filtration, and the filtrate was incorporated with 0.4 g of n-butanol to deposit crystals. The deposited crystals were collected by filtration to obtain 1.25 g of white crystals of 6-[ D(—l-Ct-(4-ethyl-2,3-dioxo-1 -piperazinocarbonylaminolphenylacetamido] penicillanic acid. Into a solution of these crystals in 30 ml of tetrahydrofuran was dropped a solution of 0.38 g of a sodium salt of 2-ethyl-hexanoic acid in 10 ml of tetrahydrofuran, upon which white crystals were deposited. The deposited crystals were collected by filtration, sufficiently washed with tetrahydrofuran and then dried to obtain 1.25 g of sodium salt of 6-[D(—)-a-(4-ethyl-2,3-di-0X0-1-piperazinocarbonylaminolphenylacetamido] penicillanic acid, melting point 183°C to 185°C (decomposition), yield 90%. 

Tetrabutylammonium fluoride (TBAF) is usually used in the form of the trihydrate or as a solution in tetrahydrofuran (THF). The pure form is difficult to isolate, owing to decomposition to FFF, tributylamine, and but-l-ene [18, 19] on dehydration. It has been used for a variety of reactions, including as a catalyst for various reactions with silicon compounds [20, 21]. One of its main uses is in the cleavage of silyl ether protecting groups [22]. 

The MOCVD of chromium is based on the decomposition of dicumene chromium, (C9Hj2)2Cr, at 320-545°C.[ ]f ] However, the reaction tends to incorporate carbon or hydrogen in the deposit. It can also be deposited by the decomposition of its carbonyl which is made by dissolvingthe halide in an organic solvent such as tetrahydrofuran with CO at 200-300 atm and at temperatures up to 300°C in the presence of a reducing agent such as an electropositive metal (Na, Al, or Mg), trialkylaluminum, and others. 

Both polymers 10 and 11 are soluble in common organic solvents, melt without decomposition, and can be drawn into the fibers. Molecular weights of the polymers 10 and 11, determined by gel permeation chromatography with tetrahydrofuran as the eluant after purification by reprecipitation from benzene-ethanol, showed a broad monomodal molecular weight distribution. The degree of polymerization depends on particle size of sodium metal. Polymers with molecular weights of 23,000-34,000 are always obtained, if fine sodium particles are used. 

Rittmeyer, P. et al., Z. Naturforsch., B Chem. Sci., 1993, 48(9), 1223 An incident during concentration of a tetrahydrofuran solution on pilot plant led to a study of the concentration dependent exothermic decomposition of the reagent and generation of safety rules. 

Isomeric tetrahydrofuran derivatives (47 and 48) are formed by copper(II)-catalyzed decomposition of methyl diazoacetate in 2-phenyloxetan (Scheme 62).99 Use of the chiral homogeneous catalyst, bis[N-(i )-a-phenylethylsali-cylaldiminato]copper(II) (49),100 causes asymmetric induction albeit with... 

Reliable mechanistic conclusions require high intrazeolite yields that account for the majority of the substrate mass balance. This can be a challenge because of the small-scale reactions often conducted for mechanistic studies. In addition, rapid removal of the products from the zeolite, and/or low conversions to decrease residence time, is occasionally necessary because of the sensitivity of the reaction products to the zeolite environment.44,45 Intrazeolite products are generally recovered by extractive techniques from either the intact zeolite, or from a mixture formed after mild digestion of the zeolite. Polar solvents such as tetrahydrofuran or acetonitrile coupled with a continuous extraction technique is in particular an effective means to remove polar products with an affinity for the interior of the zeolite.44 Zeolite digestion with mineral acids, in order to liberate the products, must be conducted with care in order to prevent acid catalyzed product decomposition or reaction.46,47... 

From the tabulated half time and decomposition of tetrahydrofuran (JACS 68 reaction and the Arrhenius parameters. 

Determine the rate equation for the decomposition of tetrahydrofuran with the aid of the tabulated data of initial pressure, half life and temperature. 

Water is, of course, a particularly difficult solvent to remove from solvates (i.e., hydrates). Thermal decomposition patterns for solvates containing such solvents as tetrahydrofuran suggest that thermal treatment of such solvates may prove a feasible route to anhydrous trihalides. 

FIGURE 7.6 Decomposition of a mixed anhydride (A) to the 2-alkoxy-5(4//)-oxazolone and the alkyl carbonate.9 The latter is in equilibrium with the anion whose reaction (B) with a second molecule of anhydride produces pyrocarbonate and the acid anion whose reaction (C) with a third molecule produces the symmetrical anhydride. The oxazolone eventually reacts with the alcohol to give the ester. (D) Acyloxonium ions formed by reaction of the anhydride with dimethylformamide and tetrahydrofuran. 

Other hydrides used for the conversion of esters to alcohols are magnesium aluminum hydride in tetrahydrofuran [89, 577] and magnesium bromohydride prepared by decomposition of ethylmagnesium bromide at 235° for 2.5 hours at 0.5mm [7055]. They do not offer special advantages (the latter giving only 35% yield of benzyl alcohols from ethyl benzoate). 

Metalated vinyl ethers are configurational stable up to —20°C in tetrahydrofuran. H-NMR measurements of 1-ethoxy-1-lithioethene TMEDA did not show any coalescence of the signals for the vinyl protons until the onset of decomposition. Thus, there is no evidence of inversion in this case . Similar configurational stability is displayed by a-lithiated thioethers in tetrahydrofuran no inversion occurs up to 0°C. On the contrary, deprotonated vinyl sulfoxides and sulfones are configurationally less stable . ... 

---