Potassium isocyanate phosgene

Dehydration Alumina (see also Dihydropyrane, preparation). Boric acid. Boron triSuoride. N-Bromoacetamide-Pyridine-SOj. Dicyclohexylcarbodiimide. Diketene. Dimethylform-amide-Thionyl chloride. Dimethyl sulfoxide. Ethylene chlorophosphite. Florisil. Girard s reagent. Hydrobromic acid. Iodine. Mesyl chloride-Sulfur dioxide. Methyl chlorosulfite. Methylketene diethylacetal. Naphthalene-d-sulfonic acid. Oxalic acid. Phenyl isocyanate. Phosgene. Phosphorus pentoxide. Phosphoryl chloride. Phthalic anhydride. Potassium bisulfate. Pyridine. Thionyi chloride. Thoria. p-Toluenesulfonic acid. p-Toluenesulfonyl chloride. Triphenylphosphine dibromide. 

This method has been applied to a monomer synthesis (2.20).61 The quaternary ammonium salt is used as a phase transfer catalyst. The potassium iodide converts the starting chloride to a more reactive iodide in situ. The alcohol traps the intermediate isocyanate before it can react with the small amount of water that has to be present. If no methanol is present, the corresponding urea is formed in up to 87% yield. If only 0.3 equivalent of water is used, the product is the iso-cyanurate, the cyclic trimer of the isocyanate. Where n = 1, the isocyanatoethyl methacrylate is a useful monomer now made with phosgene (2.21).62 Dow has patented a route from ethanolamine plus a dialkyl carbonate, followed transesterification to a methacrylate carbamate, which is py-rolyzed to the isocyanate (2.22) in 50% yield.63... 

In 1899, Erdmann obtained the same compound in good yield from anthranilic acid and phosgene and suggested the name isatoic anhydride. An alternative synthesis of isatoic anhydride [2//-3,l-benzoxazine-2,4(lH)-dione, subsequently abbreviated as lA] was found by Curtius and Semper from phthalic acid monoazide (5) via o-carboxyphenyl isocyanate. Similar rearrangements were discovered by Bredt and Hor [from potassium phthal-imide (6)] and by Mohr [from phthalimide (7)] leading to IA via a Hoffmann reaction. 

Phenyl-3-methyl-5-pyrazolone N-Phenyl-p-phenylenediamine Phosgene Phthalic anhydride Pivalyl indandione Potassium thiocyanate Propargyl alcohol n-Propyl bromide n-Propyl isocyanate Pyrogallol... 

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