Tetrahydrofuran reactions

During one run, 48 g. of product precipitated from the tetrahydrofuran reaction mixture. This precipitate was filtered, washed with saturated, aqueous sodium chloride, water, and petroleum ether (b.p. 35-60°) to yield a crystalline product, m.p. 99-106°. For recovery of the remaining product, the tetrahydrofuran filtrate was worked up in accordance with the described procedure. 

A further amount (0.4 g) of product can be isolated by evaporating the tetrahydrofuran reaction solution, mixing the oily residue with ethyl alcohol and allowing it to crystallize in a refrigerator. The overall yield is 3.4 g, equal to 68.6%. 

Complexation with zinc effectively separates the C3S5 dianion from the trithiocarbonate ion in high yield, and the material obtained is sufficiently pure for further reactions. The quaternary ammonium zincate salt is alkylated slowly but smoothly by many halides at room temperature in solvents such as acetone or tetrahydrofuran. Reaction of the zincate with benzoyl chloride followed by cleavage of the resulting benzoate by sodium ethoxide in ethanol provides the much more reactive species NajCaSs. The sodium salt is, however, very air sensitive,5 whereas the zinc salt is completely stable. 

With respect to previous work by B. Ignasiak (14), we are in agreement that alpha proton abstraction from tetrahydrofuran is occurring under Sternberg conditions. The nature of our hydrogen evolution in the model system is different, however, for it comes from a reverse quench into D2O, not from alkylation conditions. Our results implicate hydride formation during the naphthalene-sodium-tetrahydrofuran reaction. 

The two-stage process of oxymercuration-demercuration is fast and convenient, takes place under mild conditions, and gives excellent yields—often over 90%. The alkene is added at room temperature to an aqueous solution of mercuric acetate diluted with the solvent tetrahydrofuran. Reaction is generally complete within minutes. The organomercurial compound is not isolated but is simply reduced in situ by sodium borohydride, NaBH4. (The mercury is recovered as a ball of elemental mercury.)... 

The reaction between benzyl chloride and sodium phenoxide follows second-order kinetics in a variety of solvents the nature of the products, however, v tries considerably. (a) In dimethylformamide, dioxane, or tetrahydrofuran, reaction yields only benzyl phenyl ether. Show in detail the mechanism of this reaction. To what general class does it belong (b) In aqueous solution, the yield of ether is cut in half, and there is obtained, in addition, o- and p-benzylphenol. Show in detail the mechanism by which the latter products are formed. To what general class (or classes) does the reaction belong (c) What is a possible explanation for the difference between (a) and (b) Hint See Sec. 1.21.) (d) In methanol or ethanol, reaction occurs as in (a) in liquid phenol or 2,2,2-trifluoroethanol, reaction is as in (b). How can you account for these differences ... 

Dimethyl-4,8-dioxaspiro[2.5]oct-l-ene is a synthetically useful precursor for cyclopropenones because of its stability and ready availability. The sodium derivative 1 of the cyclopropenone acetal in liquid ammonia reacted with alkyl halides giving alkyl-substituted cyclopropenone acetals 3. The lithiated cyclopropenone acetal 4 was generated by treating the cyclopropenone acetal with one equivalent of butyllithium in tetrahydrofuran. Reaction of the lithium carbanion 4 with alkyl halides proceeded cleanly in the presence of two equivalents of hexamethylphosphoric triamide (Table 1, entries 1-4). The lithium compound underwent nucleophilic addition to carbonyl compounds smoothly at — 70 C giving hydroxymethyl derivatives 5 (Table 1, entries 5-10). 

The three-component reaction approach was also utilized to synthesize tetrahydrofurans. Reaction of dimethyl diazomalonate 13, aryl aldehydes and /3-nitrostyrenes afforded [66] tetrahydrofurans 14 in a highly stereoselec-... 

Alkylation.—Potassium enolates of aldehydes can be prepared by reaction of the aldehyde with potassium hydride in tetrahydrofuran. Reaction of these enolates with activated primary bromides (allyl or benzyl) and methyl iodide gives rise to C-alkylated products exclusively secondary alkyl iodides afford mixtures of C-and O-alkylated products. ... 

The most important reaction of f. is the - hydrogenation to - tetrahydrofuran. Reaction at 400-450 °C over AI2O3 with ammonia yields pyrrole and with H2S thiophene. F. can react with maleic anhydride to form a Diels Alder adduct. Both can copolymerize radically to form an alternating 1 1 copolymer, which is used as a copper-complexing agent. 

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