Methanol-triphenyl reaction

The Mitsunobu reaction was also applied to the synthesis of [ 1,2,4]triaz-ino[4,5-n]indoles (84AG517). Thus, reaction of the 2-acylindoles 127 with sodium borohydride in methanol or with lithium aluminium hydride in tetrahydrofuran gave the corresponding alcohols 128. Their cyclization with diethyl azodicarboxylate in the presence of triphenyl-phosphine gave the triazinoindoles 129. Acid treatment of the latter afforded 130 (Scheme 30). 

The formation of diphenylphosphino radicals on photolysis of triphenyl-phosphine, diphenylphosphine, and tetraphenylbiphosphine has been verified. In the case of the reactions of the phosphines, the radicals were trapped with t-nitrosobutane and the resultant nitroxyl radical [Ph2PN(0)Bu ] was identified by e.s.r. The nitroxyl radical has a small P splitting constant, demonstrating that there is no extensive delocalization onto the phosphorus atom. The e.s.r. spectrum of diphenylphosphino radicals, generated by photolysis of tetraphenylbiphosphine in benzene at 77 K, has been observed. When methanolic solutions of the biphosphine or triphenylphosphine are flash-photolysed, a transient species having Amax = 330 nm and which decays by first-order kinetics (A 4 x 10 s )... 

Finally, a reaction should be mentioned in which a nucleophile gives support to another reacting species without appearing in the final product. Diphenyl cyclopropenone interacts with 2,6-dimethyl phenyl isocyanide only in the presence of tri-phenylphosphine with expansion of the three-ring to the imine 344 of cyclobutene-dione-1,2229,230 Addition of the isocyanide is preceded by formation of the ketene phosphorane 343, which can be isolated in pure formss 231 it is decomposed by methanol to triphenyl phosphine and the ester 52. 

To a solution of triphenyl phosphite (6.2 g, 0.02 mol) and thiomethoxy-acetaldehyde (2.25 g, 0.025 mol) in glacial acetic acid (18 ml), powdered N-phenylthiourea was added in a single portion. The reaction mixture was stirred at room temperature for 30 min and then for 30 min at 80°C. After the mixture was cooled to room temperature, water (5 ml) was added and the solution was maintained at room temperature for 10 h. The precipitate was removed by suction filtration, washed with 1 1 acetic acidtwater (2 x 10 ml), dried over potassium hydroxide in an evacuated dessicator, and recrystallized from chloroform/ methanol. In this manner there was isolated pure 0,0-diphe-nyl 2-methylthio-l-(iV-phenylthioureido)ethylphosphonate (8.61 g, 94%) of mp 136 to 138°C, which exhibited spectra and analytical data in accord with the proposed structure. 

The reverse reaction of triphenyl methyl chloride (A) and methanol (B) (C6H5)3CC1 + CH3OH (C6H5)3COCH3 + HC1... 

N-Heterocyclic carbenes are an example of a family of nucleophilic catalysts [84-87]. For instance, the polymerization of p-butyrolactone was catalyzed by l,3,4-triphenyl-4,5-dihydro-l//,l,2-triazol-5-ylidene in the presence of methanol as an initiator [86]. This reaction was carried out in toluene at 80 °C. Nevertheless, an undesired elimination (Fig. 4) reaction was observed and control of the polymerization was lost. This issue was overcome by using ferf-butanol as a co-solvent, which reacts reversibly with the free carbene to form a new adduct. Owing to the decrease in the concentration of the free carbene, the elimination is disfavored and the polymerization is then under control provided that a degree of polymerization below 200 is targeted. As a rule, the reactivity of N-heterocyclic carbenes depends on their substituents. Hindered N-heterocyclic carbenes turned out to be not nucleophilic enough for the ROP of sCL. Recently, it was shown that unencumbered N-heterocyclic carbenes were more efficient catalysts [87]. 

The imine bond of 4H- and 6H- 1,3-oxazines enters into addition reactions with quinones and alcohols. Thus, for example, the triphenyl derivative (50) forms a 1 1 adduct with 1,4-benzoquinone (69LA(723)lll) and the oxazin-6-ones (51), when heated in methanol, give 2-methoxy-2,3-dihydro derivatives (Scheme 15) (72CJC584). 

Alternatively, alkyl aryl ethers can be prepared from support-bound aliphatic alcohols by Mitsunobu etherification with phenols (Table 7.13). In this variant of the Mit-sunobu reaction, the presence of residual methanol or ethanol is less critical than in the etherification of support-bound phenols, because no dialkyl ethers can be generated by the Mitsunobu reaction. For this reason, good results will also be obtained if the reaction mixture is allowed to warm upon mixing DEAD and the phosphine. Both triphenyl- and tributylphosphine can be used as the phosphine component. Tributyl-phosphine is a liquid and generally does not give rise to insoluble precipitates. This reagent must, however, be handled with care because it readily ignites in air when absorbed on paper. 

Comparing the rate constants in the foregoing table with an approximate calculated value of the encounter rate is of interest. Taking the effective radius of the solvated electron as slightly less than 3 A., and the diffusion coefficient in water as 10 4 cm.2/sec., it appears (14) that most of these rate constants are only very slightly lower than diffusion controlled. Only the reaction with triphenyl methanol is substantially slower than diffusion controlled. 

The crude reaction was filtered, and the filtrate [containing triphenyl-phosphine (75 mg, 0.28 mmol)] was concentrated in vacuo. Acetone (1.5 ml), sodium iodide (84 mg, 0.56 mmol), and high loading Merrifield resin (140 mg, 4.38 mmol of Cl/g) were added, and the slurry was allowed to stir at room temperature. After 18 h, the mixture was filtered and washed with tetrahydrofuran (3x3 ml), water (3x3 ml), acetone (3x3 ml), and methanol. Gas chromatography (GC) analysis of combined filtrates and weight gain of the resin indicated complete removal of triphenylphosine from the reaction mixture. 

Unsubstituted tetrazolyl derivative 458 was also prepared according to the following procedure (91MIP2). A solution of 5-phenyl-2-trityltetrazole in tetrahydrofuran was first treated with 1.7 M ferf-butyllithium in pentane at -25°C, in two parts. After about 30 minutes, an organolithium salt precipitated. Then a 1 M ethereal solution of zinc chloride was added to the mixture, which was then warmed to room temperature. Bis(triphenyl-phosphine)palladium(Il) chloride and 4//-pyrido[l,2-a]pyrimidin-4-one 457 were added to the reaction mixture, and after boiling for 4 hours, the 2-trityl derivative of 458 was obtained in 56% yield. Finally, detritylation with a mixture of methanol and concentrated hydrochloric acid yielded tetrazole derivative 458. 

Tetraphenyl tellurium was similarly obtained in 34% yield from triphenyl telluronium iodide and phenyl lithium1,5. Solutions of tetramethyl tellurium were prepared from trimethyl telluronium iodide and methyl lithium3. The formation of butyl triphenyl tellurium was claimed in a reaction of triphenyl telluronium iodide and butyl lithium4. Equimolar amounts of triphenyl telluronium chloride and 3,3-bis[chloromercuro]-2,4-pentadione in refluxing methanol produced 3-[chloromercuro]-2,4-dioxopent-3-yl triphenyl tellurium6. 

The Step 1 product (1.37 g Mn 26,000 daltons), 4-aminobenzoic acid (2.24 mmol), triphenyl-phosphite (5 mmol), and LiCl 0.09 g were dissolved in 30 ml of A-methyl-pyrrolidinone/pyridine solution, 80 20, respectively, and heated to 100°C for 4 hours. The reaction mixture was then precipitated in an excess of water/methanol, 1 1, filtered, and washed with methanol. The material was dried overnight under vacuum at 40°C, and the product was quantitatively isolated. 

The active metal complex could be quantitatively stripped from the silica support material by washing with methanol, and consequently, the receptor (the silica support) could be used in several, different reaction cycles. The rhodium catalyst was reused in 11 consecutive runs in batch mode for the hydroformylation of oct-l-ene (80 °C, 20-50 bar) there was no noticeable loss of activity (<0.1% per run) when a xantphos derivative was used as a ligand, and there was an approximate loss of 1% per run when a triphenyl-phosphine-derived monodentate ligand was used (Figure 32). Turnover... 

N,0 heterocyclic carbenes have also been shown to form adducts with triorganoboron complexes. Triphenyl-boron carbene adducts (62) were isolated from the reaction of an isocyanide adduct of BPhs with methanol (equation 6), in the presence of a catalytic amount of KF. An X-ray structural determination showed that (62) consists of a tetrahedrally coordinated boron atom with all four B C bond distances equal (within experimental error). 

On the other hand, generation of free carbenes can be thermally achieved from C-protected NHC . In 1995, Enders reported the thermal elimination of methanol from 5-methoxy-l,3,4-triphenyl-4,5-dihydro-l//-l,2,4-triazole (12) affording the corresponding carbene l,2,4-triazol-5-ylidene (13) in quantitative yield (Scheme 2). Methanol adduct (12) is easily synthesized from reaction of triazolium perchlorate (11) and NaOCH3 in methanol. 

In commercial practice, all PET is made using an antimony compound for the final polycondensation stage. The transesterification reaction between DMT and the glycol is catalysed by salts of manganese, zinc, calcium, cobalt, or other metals. At the end of the ester-interchange stage, when essentially all of the methanol has been evolved, the transesterification catalyst is converted to a catalytically inactive and substantially colourless form by reaction with a phosphorus compound such as triphenyl phosphate or phosphite. Polyesters of 1,4-cyclo-hexanedimethanol and DMT or TA are made using complex titanium catalysts. 

The reaction of 2,4,6-triphenyl-X -phosphorin (20) with 2-thiophenyl-, 2-benzofuryl-2, 2-benzo-1,3-thiazolyl-, and ferroceny1-lithium affords the corresponding 1-substituted 1,2-dihydro-X phosphorin (21), which on treatment with mercury (II) acetate in methanol gives the related X --phosphorin, for example, 1-methoxy-1-(2-thiophenyl)-2,4,6--triphenyl-X -phosphorin (22) (Markl, C. Martin, and W. Weber, Tetrahedron Letters, 1981, 1207). 

---