Tetrahydrofuran reagents

Tetrahydrofuran, reagent grade, was refluxed over and distilled from lithium aluminum hydride immediately prior to use. 

Tetrahydrofuran (reagent grade) was dried by distillation from sodium/benzophenone ketyl and freshly distilled before use. 

Terminal alkyne anions are popular reagents for the acyl anion synthons (RCHjCO"). If this nucleophile is added to aldehydes or ketones, the triple bond remains. This can be con verted to an alkynemercury(II) complex with mercuric salts and is hydrated with water or acids to form ketones (M.M.T. Khan, 1974). The more substituted carbon atom of the al-kynes is converted preferentially into a carbonyl group. Highly substituted a-hydroxyketones are available by this method (J.A. Katzenellenbogen, 1973). Acetylene itself can react with two molecules of an aldehyde or a ketone (V. jager, 1977). Hydration then leads to 1,4-dihydroxy-2-butanones. The 1,4-diols tend to condense to tetrahydrofuran derivatives in the presence of acids. 

Grignard reagents (Section 14 4) Grignard reagents are prepared in a manner similar to that used for organolithium compounds Di ethyl ether and tetrahydrofuran are appro priate solvents... 

Suitable strong bases include the sodium salt of dimethyl sulfoxide (m dimethyl sulfox ide as the solvent) and organohthmm reagents (m diethyl ether or tetrahydrofuran)... 

There are five components to the cost of using a Grignard reagent (/) magnesium metal, (2) the haUde, (J) the solvent, (4) the substrate, and (5) disposal of the by-products. The price of magnesium in mid-1992 was 3.20/kg, having risen from 1.20/kg in 1966 to 1.36/kg in 1970 and 2.90/kg in 1979. Prices for tetrahydrofuran and diethyl ether, the two most commonly used solvents, have also increased (Table 3) in the same period. The cost of the hahde depends on its stmcture, but as a general rule the order of cost is chloride < bromide < iodide. 

Other procedures have also been reported (38,110,111). The properties and chemistry of 9-BBN have been reviewed (112). The reagent is a white crystalline soHd, stable indefinitely at room temperature, soluble in hexane, carbon tetrachloride, benzene, tetrahydrofuran, and diethyl ether. It exists as a... 

Excess alkylating reagent is required if the tetraorganotin is desired as the exclusive product. In commercial practice, the stoichiometry is kept at or below 4 1, since the cmde product is usually redistributed to lower organotin chlorides in a subsequent step and an ether is used as the solvent (86). The use of diethyl ether in the Grignard reaction has been generally replaced with tetrahydrofuran. 

Lithium metal in tetrahydrofuran can also be used as the coupling reagent, and unsymmetrical ditins can be prepared when the reaction is conducted in stages (162,163). 

It resembles tetracyanoethylene in that it adds reagents such as hydrogen (31), sulfurous acid (31), and tetrahydrofuran (32) to the ends of the conjugated system of carbon atoms suffers displacement of one or two cyano groups by nucleophilic reagents such as amines (33) or sodiomalononittile (34) forms TT-complexes with aromatic compounds (35) and takes an electron from iodide ion, copper, or tertiary amines to form an anion radical (35,36). The anion radical has been isolated as salts of the formula (TCNQ) where is a metal or ammonium cation, and n = 1, 1.5, or 2. Some of these salts have... 

In ether or tetrahydrofuran organolithium reagents cleave the silicon-oxygen bond in hexamethylphosphoramide, they react at the carbon atom. ... 

This complex should be used when the organolithium is in solution in a hydrocarbon solvent. For organolithium reagents prepared in ether (see Note 4), the same complex may be used or, more conveniently, copper iodide (Cull can be used. The Cul purchased from Prolabo or Merck 4 Company, Inc. may be used directly. Other commercial sources of Cul (Fluka, Aldrich Chemical Company, Inc., Alfa Products, Morton/Thiokol, Inc.) furnish a salt which affords better results when purified. 1 mol of Cul is stirred for 12 hr with 500 ml of anhydrous tetrahydrofuran, then filtered on a sintered glass funnel ( 3), washed twice with 50 ml of anhydrous tetrahydrofuran, once with 50 ml of anhydrous ether and finally dried under reduced pressure (0.1 imO for 4 hr. 

Carbonate ionophore I [ETH 6010] (heptyl 4-trifluoroacetylbenzoate) [129476-47-7] M 316.3, b 170°/0.02 Torr, d 0.909. Purified by flash chromatography (2g of reagent with 30g of Silica Gel 60) and eluted with EtOAc/hexane (1 19). The fractions that absorbed at 260nm were pooled, evapd and dried at room temp (10.3 Torr). The oily residue was distd in a bubbled-tube apparatus (170°/0.02 Torr). Its IR (CHCI3) had peaks at 1720, 1280, 940cm and its sol in tetrahydrofuran is 50mg/0.5mL. It is a lipophilic neutral ionophore selective for carbonate as well as being an optical humidity sensor. [Anal Chim Acta 233 41 1990.]... 

A reagent grade of tetrahydrofuran (b.p. 65-66°) was distilled from lithium aluminum hydride before use,... 

Apply 10% 3,5-dinitrobenzoyl chloride solution [72] in p-xylene — tetrahydrofuran (15-1-2), followed by sample solution allow to react destroy excess reagent with 10% sodium hydroxide solution. 

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. ... 

A solution of 3jS-hydroxy-5a-androstan-17-one tosylate (193, 60 mg) in tetrahydrofuran (10 ml, freshly distilled from lithium aluminum hydride) is added dropwise to a boiling suspension of lithium aluminum deuteride (60 mg) in tetrahydrofuran (10 ml). The resulting suspension is heated under reflux for 30 min and after cooling the excess reagent is decomposed by the careful addition of a few drops of water. The heating is continued for a few minutes to coagulate the inorganic salts which are removed by filtration... 

Although steroidal spiro oxiranes are difficult to obtain stereochemically pure by peracid epoxidations of exocyclic methylenes,the recently developed methylene transfer reagents, dimethylsulfonium methylide and di-methylsulfoxonium methylide in tetrahydrofuran, proved useful in the stereoselective transformation of steroid ketones to a- and -oxiranes, (87) and (88), respectively. ... 

Ionic Inflate derivatives of nonmetallic elements such as selenium, sulfur, phosphorus, and iodine form an important class of reagents lor organic chemistry. Highly electrophilic phenylselenyl triflate can be used in the cyclization of 5- and 6-hydroxyalkenes, affording the corresponding tetrahydrofurans and pyrans [132] (equation 68). 

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