Methane reaction with, phosgene

The first methanes involved the reaction of isocyanate with simple alcohols and amines. They were of sufficient economic value to foster the development of a number of isocyanates, including the aromatics that play dominant roles in modem polyurethanes. An isocyanate is made by reacting an amine with phosgene. 

The reactions of phosgene with alkanes have been surprisingly little studied. In some early work, phosgene is reported to react with methane on exposure to sunlight to give some ethanoyl chloride [313a,888]. No thermal reaction was observed by Berthelot between... 

Curiously, the reaction of phosgene with the first member of the aldehyde series, methanal, was not properly investigated until the 1980s, the system only then becoming the subject of patent disclosure [1559aa,1762],... 

MDI Chemistry. Methylene diphenylene isocyanates are a product of the reaction of aniline, formaldehyde and phosgene. The first step is the reaction of aniline (made by hydrogenation of nitrobenzene) with formaldehyde to form the intermediate bis(aminophenyl)methane. The chemistry is shown in Eq. (2). The bis(aminophenyl)methane is then reacted with phosgene to yield dimeric and trimeric isocyanates as shown in Eq. (3) [4]. 

By the aid of a modified peptide synthesizer solutions of two moles of Boc- or Ddz-amino acid salts (sodium- or triethylammonium form) in tetrahydrofuran or dichloro-methane at —40 °C are mixed for 5 minutes with one mole of phosgene in the same solvent at —40 °C, controlled by the punched tape program of the synthesizer (Fig. 44). The solution of the symmetric anhydride is added at —40 C to the gel polymer, which is contained in the centrifugal reactor (see p. 75) and is allowed to warm up to the cooling water temperature level (9—13 C) of the reactor during the peptide synthesis period of 30 minutes. Since the mode of action of the centrifugal reactor renders it possible to perfuse an external IR flow cell with the reaction solution, we are in a position to monitor directly the quality of the symmetric anhydride and its consumption, watching the characteristic absorptions on 1,830 and 1,760 cm [71]. In several cases the symmetric anhydrides were isolated in crystalline or solid form for characterization (Table 6). 

Typical procedure. Di-2-pyridyl carbonate, DPC, 725 [638] A solution of phosgene (for a safe source, see Chapter 7) (2.5 m in toluene, 2 mL, 5.0 mmol) was diluted with dichloromethane (8 mL) and then a solution of 2-pyridinol 853 (950 mg, 10 mmol) and triethylamine (1.214 g, 10.2 mmol) in dichloromethane (20 mL) was added at 0 °C. The reaction mixture was stirred at 0 °C for 1 h, then washed with cold 5% NaHCOs solution (20 mL) and cold saturated brine (20 mL), dried over MgS04, and filtered. The filtrate was concentrated to dryness to give di-2-pyridyl carbonate, DPC, 725 (972 mg) in 90% yield. It was recrystallized from dichloro-methane/petroleum ether (811 mg, 75%) mp 84—86 °C. 

Typical procedure. N,N -Bis(4-amino-2,6-dimethylpyrimidine) urea 1036 [759] A solution of phosgene (for a safe source, see Chapter 7) (9.9 g, 0.1 mol) in tetrachloro-methane (50 mL) was added dropwise to a stirred suspension of 1035 (0.04 mol) in dichloromethane (300 mL dried over 4 A molecular sieves). The reaction temperature was kept at 25-30 °C by cooling with ice/NaCl. Stirring was maintained at room temperature for 3-5 h, and then the precipitate was isolated, thoroughly stirred with H2O (200 mL), collected by filtration once more, washed with a little H2O, and dried at 60-70 °C. In the case of compound 1036 (R = Cl), the precipitate obtained was successively stirred with ethanol (60 mL) and H2O (100 mL) yield 80-82%. 

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