Tetra hydrofuran derivative

By the same type of epoxide rearrangement, other bicyclic and tricyclic orthoesters can be synthesized [80]. However, the orthoesters are only the kinetic products and, if not sufficiently inert, can further rearrange under reaction conditions to more stable tetra-hydrofuran derivatives (cf. Scheme 8.40). In many cases, the tetrahydrofurans are the... 

Cyclizations arising by intramolecular radical addition have been widely employed in the synthesis of oxygen and sulfur heterocycles. The tetra-hydrofuran derivatives (494) have been prepared in this way via alkoxyl radicals, generated in turn by photolysis of the unsaturated nitrites (495).431 Bridged oxabicyclic compounds have been similarly prepared,432 and the photodecomposition of a nitrite has been employed in the synthesis of the... 

Hydroxy-a,) -ethyleneketones from cyclic ketalethers s. 16, 317 di(tetra-hydrofuran) derivatives s. V. M. Micovic et al., Tetrah. Let. 1965, 1559... 

Zuo and Louie also found that NHC-Ni complexes catalyzed the rearrangement of cyclopropylen-yne derivatives. However, the selectivity of the reaction was strongly dependent on the NHC-Ni catalyst as well as on the substrate substitution. With a SIPr/Ni 1 1 system, a hindered vinylcyclo-propylene-yne gave the isomerized seven-membered ring as the sole product while the corresponding methyl derivative afforded a di-substituted tetra-hydrofuran derivative. The authors then described a successful and general access to the latter by using the ItBu/Ni 1 1 system (Scheme 10.10). 

Keumi et al. (1989) describe hydro-de-diazoniations of arenediazonium tetrafluo-roborates using chlorotrimethylsilane, (CH3)3SiCl), in tetrahydrofuran or tetra-hydrofuran/A A-dimethylformamide mixtures. Excellent yields were obtained with polycyclic arene derivatives such as 2-fluorene-, 2-fluorenone-, and 1-pyrenediazo-nium tetrafluoroborate and other similar diazonium salts. In a modification of this method 2-halogenofluorenones can be synthesized (see Sec. 10.6). 

That the anhydro product from ribitol is a derivative of 1,4-tetra-hydrofuran was established10 from the results of periodate oxidation (consumption of 1 mole of periodate per mole, with no formation of... 

When all monomer is consumed in polymerisation then the positive charge almost certainly resides on some small molecular species, not a polymer molecule. This is not necessarily so however, in the case of the polymerisation of tetra-hydrofuran (THF), where the presence of living polymeric cations was demonstrated originally by Dreyfuss and Dreyfuss (50). Sangster and Worsfold (27) have since been able to make direct conductance measurements, and evaluate Kd for the living oligomeric oxonium ion pair (BFJ counterion) derived from THF in methylene chloride at —0.5° C. 

As shown in Table 4, the real promise of succinic acid lies in its derivatives. A DOE-funded collaboration among Oak Ridge National Laboratory Argonne National Laboratory Pacific Northwest National Laboratory National Renewable Energy Laboratory and Applied CarboChemicals, Inc. investigated succinic acid derivatives such as tetra-hydrofuran, 1,4-butanediol, y-butyrolactone, and N-methyl pyrrolidone. More recently, Applied Carbochemicals has pursued succinate salts that can serve as de-icers and herbicide additives (40,41). 

Singlet as well as triplet excited states of oxiranes undergo C—C bond scission to produce carbonyl ylides which, upon cydoaddition with dipolarophiles, give tetra-hydrofuran (THF) derivatives. For example, trans- or ds-stilbene oxide on direct photolysis using 254 nm light in the presence of methyl acrylate gave diastereomeric... 

Trimethylsilyl derivatives are prepared by treatment with BSA alone [310,311] or with the addition of TMCS [312,314] in a suitable solvent (acetonitrile, pyridine, tetra-hydrofuran) or even without a solvent. For completion of the reaction, 10—20 min at 50°C are necessary [312], but as little as 30 min at 150°C has been reported for a stoppered vial with the use of a solvent [311], BSA alone can be used to advantage if pico-mole amounts are to be derivatized. The reaction products are said to decompose in dilute solutions even though pure BSA is used for dilution. At concentrations around 1 ng//d, up to 40% decomposition of the products is observed if diluted with BSA— acetonitrile (1 4), 100% decomposition occurs in 20 min. Of other silylating agents, e.g., HMDS and TMCS have been tested, but conversion into derivatives was not complete [311]. Silicone stationary phases of the SE-30, OV-1 and similar types have been used in the analysis. In most instances, temperature programming is required. Using the FID (in almost all instances), the detection limit is about 20 ng for T4 and 5—20 ng for T3, whereas with the aid of an ECD amounts about two orders of magnitude smaller can be detected [310,314]. Fig. 5.21 demonstrates a typical separation of five iodoamino acids and Tyr on 0.5% of SE-30. 

Dehydrochlorination of the phosphine derivative 181 with DBU in tetra-hydrofuran at ambient temperature gave 182 in almost quantitative yield (78JA4886). 

The dicyclopentadienyl derivatives of these elements which are known at the present time (those of magnesium and calcium) are in many respects similar to those of the alkali metals, being colorless, saltlike compounds. The magnesium compound was successfully prepared by the interaction of sodium cyclopentadienyl and magnesium bromide in tetra-hydrofuran 214), by thermal decomposition of cyclopentadienyl magnesium bromide 214) and, recently, by the action of cyclopentadiene... 

Treatment of the triflate 9 with the sodio derivative of r-butyl dimethoxphosphorylacetate in dimethylformamide (DMF), at room temperature for 20 h in the presence of a crown ether, gives the epimeric phosphonates 10 in 81% yield [9]. Cleavage of the glycosidic bond by hydrogenolysis then affords the hemiacetals 11 which, with sodium hydride in tetra-hydrofuran (THF), give the C-6 phosphonium ylid, which reacts with C-1 in the aldehydo form to afford the alkene 12 in 73% (from the glycoside 10 Scheme 2). The cyclization... 

The and A -unsaturated acids [62, 63] and unsaturated alcohols [62] yield tetra-hydrofuran-2-one or tetrahydropyran-2-one and tetrahydrofuran or tetrahydropyran derivatives, respectively, when electrolyzed in MeOH or CH2CI2 containing PhSeSePh and NH4Br or Et4NBr. Examples of products and respective precursors are shown in Eqs. (28) and (29). 

Very few studies have considered the behavior of ionomers in relatively polar solvents, i.e., solvents with high dielectric constants, e. Schade and Gartner(8) compared the solution behavior of ionomers derived from copolymers of styrene with acrylic acid, methacrylic acid, or half esters of maleic anhydride in tetra-hydrofuran (THF), a relatively non-polar solvent (e 7.6), and dimethyl formamide (DMF), a polar solvent (e = 36.7). They ob-... 

Procedures (i) Silylation. Hexamethyldisilazane was used to prepare trimethylsilyl derivatives of the amines according to the method of Luukkainen et al. (L13). Homing et al. (H15) used acetone or tetra-hydrofuran (THF) as solvent. However, the present writer believes that acetone should be avoided here owing to the possibility of eneamine formation. 

Whereas cycloaddition of azomethine ylids were usually conducted with careful exclusion of water, it was recently shown that the cydoaddition in water-tetra-hydrofuran solution of stabilized ylids derived from ethyl sarcosinate with several dipolarophiles can occur in excellent yields [53]. 

Caution. Attention is drawn to the toxicity of metal carbonyls. Volatile metal carbonyl derivatives are likely to be particularly dangerous and should be handled only in a vacuum system or using an efficient fume hood. Hazards arising during the purification of tetra-hydrofuran, required as a solvent for this reaction, have been emphasized in a previous volume of this series (Vol. XII, p.317). 

Fluorinated compoimds I, III, IV, and V were dissolved in tetra-hydrofuran solutions of the PVeC copolymer in concentrations up to 1% by weight of the polymer. Of these additives, the 3-methyl glutarate (in), ethane sulfonate (V), and tricarballylate (I) derivatives failed to modify the wettability of the polymer surface. However, the tetra-chlorophthalate derivative (IV) caused a marked decrease in the wettability of the polymer (see Table IV, last column). In Figure 3 the graph of cos 6 vs. 7lv° n-alkanes on the resulting surface shows that... 

In contrast to the oxidative cleavage of cyclic sulfites with chlorine, the photochemical chlorination of 1,3,2-dioxathiolane 2,2-dioxide gave a 4,5-dichloro derivative, which was formed via a radical process. Subsequent dechlorination of the dichloro compound with magnesium in refluxing tetra-hydrofuran gave 1,3,2-dioxathiole 2,2-dioxide (Scheme 78) (68JA2970). 

Spectrophotometric detection is generally used and the choice of solvents is limited to those with low absorption properties. Especially, acetonitrile, tetra-hydrofuran, methanol, or isopropanol and, less commonly, dioxan (which can be used for the separation of cardiac glycosides and derivatives of amino acids) have been found to be sufficiently selective in most cases. Water is used to adjust solvent strength and the addition of acid (preferably orthophosphoric acid, although acetic and formic acids can be used, especially if MS detection is hyphenated) or buffer in RPLC will decrease peak tail. A typical sample of the use of an ammonium buffer is reported for the HPLC analysis of both neutral and acid ginsenosides (Figure 3). 

The electrocyclic opening of cyclopropane derivatives containing internal nucleophilic groups provides a new route to vinyl lactones, tetrahydropyrans, and tetra-hydrofurans (Danheiser et al. 1981). The silver salt initiates the opening of the ring... 

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