Silver isocyanate

Iodine isocyanate, from silver isocyanate and iodine, 51,... 

Silver isocyanate, with iodine to give iodine isocyanate, 51, 112... 

Reaction with silver isocyanate or silver thiocyanate yields phosphorus triisocyanate or phosphorus trithiocyanate ... 

Owing to the rapid decomposition of the cyanate ion in water, the use of aprotic solvents was necessary for the preparation of the Ag(NCO)J ion. Since alkali cyanates are poorly soluble in aprotic solvents, the cyanate salts used were the tetraethylammonium, tetramethylammonium and tetraphenylarsonium cyanates. Either dry acetone or acetonitrile could be used as solvent as silver isocyanate was reasonably soluble in both. Once prepared the silver salts were found to be light- and moisture-sensitive.136-137... 

Addition of IN3 to 1-phenylcyclohexene affords the expected Markovnikov product corresponding to the anfi-mechanism. Although further chemical transformations of the product seemed to be in conflict with the proposed structure, extensive 15N NMR experiments finally convinced the authors that the original structure was correct172,193. Iodination of cyclohexene promoted by silver isocyanate was used to prepare the corresponding l rans-i odocy an ate194. 

This reaction is a consequent continuation of an already described lactone synthesis263 where 3- or 7-halo-esters were treated with silver isocyanate to form the corresponding /3- or 7-lactone (Scheme 75). Via this method TMS /3-bromo-propionate (500) affords /3-propiolactone (464)263 ... 

Related 2-deoxy-2-ureido-D-glucose derivatives can be obtained by direct reaction of phenyl isocyanate or silver isocyanate with LXXXIII, the former giving LXXXVIII, whereas the latter affords the free 2-ureido derivative LXXXIX.164,188 This reaction contrasts with the behavior of LXXXIII with isothiocyanates, which react at Cl (see p. 244). 

Phosphorus(III) isocyanate was first prepared by the reaction of phosphorus(III) chloride with silver isocyanate in warm benzene.1 A later modification utilized phosphorus(III) iodide as a starting material with nitromethane as solvent.2... 

The synthesis from silver isocyanate and phosphorus(III) chloride has proved the most dependable and gives the highest... 

Silver isocyanate is prepared by the method of Neville and McGee.6 The material obtained from this preparation should be thoroughly dried in a vacuum desiccator over P4Oi0 for at least 2 days before use. 

Into the flask is placed 100 g. (0.66 mole) of silver isocyanate and 100 ml. of dry benzene. A mixture of 30 g. (0.22 mole) of phosphorus(III) chloride and 20 ml. of dry benzene is placed in the dropping funnel. The entire system is then flushed once more with nitrogen. The mixture of phosphorus(III) chloride-benzene is allowed to flow in dropwise, with stirring, over a period of half an hour. ... 

Rapid darkening of the silver isocyanate at this point indicates incomplete drying, and a significantly lower yield of product can be expected. 

In a benzene solution the reaction between silver isocyanate and ASCI3 forms a precipitate of AgCl-As(ONC)3 is obtained upon evaporation of the benzene in the form of a white, crystalline solid which melts at 97.1 °C. The cyanate Ag(CNO)3 is obtained by heating the isocyanate to 230 °C under reflux. At this temperature it isomerizes to the cyanate. Ag(CNO)3 decomposes rapidly in the presence of water or acid. 

See also Silicon tetraisocyanate and methylsilicon isocyanates (includes silver isocyanate), synthesis 6... 

Silicon tetraisocyanate and methylsilicon isocyanates, of the type (CH3) Si(NCO)4 (n = 1, 2, or 3), were first prepared in 75 to 90% yields by treating silicon(IV) chloride or the appropriate methylchlorosilane with silver isocyanate in anhydrous benzene. Forbes and Anderson report that much smaller yields are obtained when lead cyanate is used instead of silver isocyanate. The following procedure, however, when performed with lead cyanate, produces 52 to 71% yields of the silicon isocyanates. Comments on the use of less expensive lead cyanate are therefore included along with the silver isocyanate method of preparation. 

Silver isocyanate is prepared by adding a solution of 487 g. (6.0 mols) of potassium cyanate in 1 1. of distilled water to a well-stirred solution of 1019 g. (6.0 mols) of silver nitrate in 1 1. of distilled water. The temperature of the mixture is kept below 25° by cooling in an ice bath as nec-... 

High yields of the silicon isocyanates are obtained when freshly prepared silver isocyanate or lead cyanate is employed. When the silver or lead salt is several weeks old, or is dried in an oven, the yields of silicon isocyanates are about 20% lower. 

Finely powdered silver isocyanate (660 g. 4.4 mols 10% theoretical excess) is mixed with 800 ml. of anhydrous sodium-dried benzene contained in a 3-1. three-necked standard-taper flask fitted with a motor-driven stirrer, a thermometer, a 125-ml. dropping funnel, and a 300-mm. Allihn condenser topped by a Drierite-filled tube. Silicon-(IV) chloride (170 g. 1.0 mol) is added dropwise to the suspension over a 30- to 45-minute period with rapid stirring. The reaction is strongly exothermic, and the temperature of the mixture must be maintained below 45° by cooling the bottom of the flask, as necessary, in an ice-water bath. After the silicon (IV) chloride has been added, the mixture is heated at gentle reflux for 3 hours, with con-... 

A 10% excess of silver isocyanate or lead cyanate has repeatedly been found to give the highest yields of product. A 25% excess produces no greater yield. Stoichiometric amounts produce slightly lower yields. On the other hand, a 10% excess of silicon(lV) chloride results in only a 40% yield of silicon tetraisocyanate. ... 

When freshly prepared lead cyanate (642 g. 2.2 mols 10% theoretical excess) is employed in the above procedure instead of silver isocyanate, the reaction is only slightly exothermic. The silicon(IV) chloride can therefore be added at a fairly rapid rate after the reaction has been initiated by heating to 35 to 40". The mixture is then refluxed with vigorous stirring for 3 hours. After the benzene is distilled, the 3ueld of silicon tetraisocyanate is 121 g. [61.8% based on silicon(IV) chloride]. 

Because trimethylsilicon isocyanate boils at 91 , making its separation from benzene somewhat difficult, this isocyanate is more readily prepared by using the same volume of xylene instead of benzene. With this modification, the yield of trimethylsilicon isocyanate is 91% from silver isocyanate, or 71% from lead cyanate. Anal. Calcd. for (CH3)3SiNCO N, 12.2 Si, 24.4. Found (by checkers) N, 11.8 Si, 23.6. 

Prr olaotwe is formed when silver isocyanate ia reacted with trimethjisiljd 2>bronioprcfuonaite. i ... 

Silver isocyanate, with iodine to give iodine isocyanate, 51,112 Sodium, with l-bromo-3-dilorocydo-butane to give bicyclo [1.1.0 ]-butane, 51,55 Sodium amalgam, 50,50, 51 Sodium amide, with 2,4-pentanedione and diphenyliodonium chloride to give l-phenyl-2,4-pentane-dione, 51,128 Sodium azide, 50,107 with mixed carboxylic-carbonic anhydrides, 51, 49... 

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