Tetrahydro tetrahydrofurans

Furan, tetrahydro-, tetrahydrofuran, oxolane, 1,4-epoxybutane, butylene oxide 1109-99-9)... 

Furanmethanol, tetrahydro-, tetrahydrofuran-2-methunol, tetrahydrofurfuryl alcohol, tetrahydro-2-furancarbinol, hydroxymethyltetrahydrofuran (97-99-4] FEMA 3056... 

The absence of such a means for indicating hydrogenation of other monocyclic heterocycles forces the use of tetrahydro-, hexahydro- or perhydro- prefixes. The resulting names are, unfortunately, cumbersome, and in practice are inevitably replaced by acronyms, such as THF for tetrahydrofuran, when the substance must be referred to frequently. 

A solution of 1.5 g of dl-3-(1, r-dimethylheptyi)-6,6a,7,8-tetrahydro-1-hydroxy-6,6-di-methyl-9H-dibenzo(b,d] pyran-9-one in 50 mi of anhydrous tetrahydrofuran (THF) was added dropwise to a soiution of iithium metal in liquid ammonia at -80°C. Excess iithium metal was added in chunks to the solution as the biue color, indicating free dissolved lithium, disappeared. After the addition was complete, ammonium chloride was added to react with any excess lithium metal still present. 

The phosphorodichloridate was hydrolyzed by adding to a stirred solution of sodium carbonate (253 grams) in water (2.9 liters). After 1 hour the solution was cooled and acidified with a solution of concentrated sulfuric acid (30 ml) in water (150 ml) and then extracted with a mixture of tetrahydrofuran and chloroform (2.3/1 3 x 1 liter). The tetrahydro-furan/chloroform liquors were bulked and evaporated to dryness to give a light brown oil. This was dissolved in water (1 liter) and titrated with 2N sodium hydroxide solution to a pH of 4.05 (volume required 930 ml). The aqueous solution was clarified by filtration through kieselguhr and then evaporated under reduced pressure to a syrup (737 grams). 

The addition of a cyclic vinyl sulfoxide anion to aldehydes has been reported only once14. Interestingly, 2,3,4,5-tetrahydro-l//-thiepane S-oxide cannot be metalated by lithium diiso-propylamide in tetrahydrofuran at — 78 °C. At higher temperatures ( — 20° to 0°) a white polymeric precipitate is formed. This polymeric product is also formed when the sulfoxide is treated with butyllithium or. wr-butyllithium in tetrahydrofuran even at — 78 C. However, metalation can be accomplished with. sec-butyllithium using an excess of N,N,N, N -tetramcthylethylenediamine in tetrahydrofuran at —78 C. In this case, a pale yellow solution is formed immediately and upon addition of benzaldehydc instantaneous dccolorization occurs yielding a mixture of diastereomeric alcohols in 90% yield. 

C 7H,203 5675-70-7) see Bisantrene (R)-(-i)-tetrahydrofuran-2-carboxylic acid (CjHgOj 87392-05-0) see Faropenem sodium ( )-tetrahydrofuran-2-carboxylic acid (CjHgOg 16874-33-2) see Alfuzosin Faropenem sodium tetrahydro-2-furancarboxylic acid anhydride with ethyl hydrogen carbonate (CgHijO, 167391-50-6) see Alfuzosin... 

Analogous photoadditions have been observed on irradiation of pyrimidine and purine bases in ethers and amines. Irradiation of 1,3-dimethylur-acil (314) in tetrahydrofuran leads to the formation of 5- and 6-(tetrahydro-furan-2-yl)-5,6-dihydrouracils 315 and 316.261 Similarly, solvent adducts arising by way of initial hydrogen abstraction have been obtained on irradiation of pyrazine derivatives in diethyl ether or tetrahydrofuran.262 The... 

Fluoride ion catalyzes the hydrosilylation of both alkyl and aryl aldehydes to silyl ethers that can be easily hydrolyzed to the free alcohols by treatment with 1 M hydrogen chloride in methanol.320 The most effective sources of fluoride are TBAF and tris(diethylamino)sulfonium difluorotrimethylsilicate (TASF). Somewhat less effective are CsF and KF. Solvent effects are marked. The reactions are facilitated in polar, aprotic solvents such as hexamethylphosphortriamide (HMPA) or 1,3-dimethyl-3,4,5,6-tetrahydro-2(l //)-pyrirnidinone (DMPU), go moderately well in dimethylformamide, but do not proceed well in either tetrahydrofuran or dichloromethane. The solvent effects are dramatically illustrated in the reaction of undecanal and dimethylphenylsilane to produce undecyloxyphenyldimethylsi-lane. After one hour at room temperature with TBAF as the source of fluoride and a 10 mol% excess of silane, yields of 91% in HMPA, 89% in DMPU, 56% in dimethylformamide, 9% in tetrahydrofuran, and only 1% in dichloromethane are obtained (Eq. 164).320... 

Mono(2,6-dimethoxybenzoyl)tartaric acid Butanedioic acid, 2-[(2,6-dimethoxybenzoyl)oxy-3-hydroxy-, [R-(R, R )]- (12) (116212-44-3) 2,6-Dimethoxybenzoic acid Benzoic acid, 2,6-dimethoxy- (8,9) (1466-76-8) Trifluoroadetic anhydride Acetic acid, tritluoro-, anhydride (8,9) (407-25-0) Borane-Tetrahydrofuran Furan, tetrahydro-, compd. with borane (1 1) (8,9) (14044-65-6)... 

Borane-tetrahydrofuran complex Furan, tetrahydro, compd. with borane (1 1) (8,9) (14044-65-6)... 

Figure 4.2 Predicted chromatographic behaviour in aqueous acetonitrile and tetrahydro-furan of model compounds whose log P values are 1, 3, and 5. Column, 5 pm octadecyl-bonded silica gel (LiChrosorb LC-7), 25 cm x 4.1 mm i.d. Compounds and eluent , polycyclic aromatic hydrocarbons and alkanols in aqueous acetonitrile, O, alkanols in aqueous tetrahydrofuran and O, polycyclic aromatic hydrocarbons in aqueous tetrahydrofuran.

Monensin belongs to the family of polyether ionophores. These compounds consist of a series of tetrahydrofuran and tetrahydro-pyran rings and have a carboxyl group that forms neutral salts with alkali metal cations. Their three-dimensional structure presents a lipophilic hydrocarbon exterior with the cation encircled in the oxygen-rich interior. They probably act by transporting cations through the lipid bi-layer of cell membranes, thereby preventing the concentration of potassium by the cells. Evidence for this is... 

Reacts with calcium and magnesium hydrides in tetrahydrofuran forming tetrahydro aluminates, Ca(AlH4)2 reacts with hydrides of alkali metals in ether forming aluminum hydride ... 

Tetrahydro-l,4-oxazin-2-ones can be deprotonated and then reacted with electrophiles. Thus, for example, the nonlabeled analog of compound 81 was deprotonated at the 3-position with sodium hexamethyldisilazide and ethylated using ethyl iodide. The reaction was performed in a 1 10 mixture of hexamethylphosphoramide (HMPA) and tetrahydrofuran <1998T10419>. If a dihalide is used and the oxazine has a free 4-nitrogen, cycloalkylation can be achieved as shown in the reaction of 219 to give 220 (Equation 17) <1993LA477>. 

Similarly, very useful yields and diastereoselectivities were observed on alkylation of (5R)-2,3,5,6,-tetrahydro-5-phenyl-A-(ter/-butoxycarbonyl)-4/f-l,4-oxazin-2-one (7)92, The latter is available from (A)-phenylglycinol and phenyl 2-bromoacetate with subsequent protection of the amino group. The influence of the base, the counterion and the solvent was studied for this example. Sodium hexamethyldisilazanide in tetrahydrofuran/dimethoxyethane turned out to be by far the best conditions for deprotonation. Also, it seems to be essential that the base is added to the chilled solution of 7 and not vice versa. 

After selective generation of the syn- or anH -enolate of an amide, it is usually reacted with a haloalkane, often the iodide. Allylic and benzylic bromides also react satisfactorily, and dimethyl and diethyl sulfate have also been used in some cases. A solution of the alkylating agent in an ethereal solvent, usually tetrahydrofuran, is added to the enolate, usually at low temperature. A polar, aprotic cosolvent, such as hexamethylphosphoric triamide, is frequently used as an additive in the alkylation step. The use of this suspected carcinogen is prohibited in some countries, which limits the usefulness of many of the reactions described below. However, similarly effective in many cases are some ureas, such as the commercially available 1,3-dimethyl-3,4,5,6-tetrahydro-2(l//)-pyrimidinone (DMPU)12. 

Tricyclic lactams, such as exo- and c r/n-3a,4,7,7a-tetrahydro-4,7-methano-2-phenyl-1 //-isoin-dolc-1,3(2//)-dione (4), have been transformed into their dianions by treatment with slightly more than two equivalents of lithium diisopropylamide in tetrahydrofuran, sometimes with hexamethylphosphoric triamide as cosolvent. Alkylation with iodomethane or the bifunctional 1,4-dibromobutane leads to dialkylated products2. 

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