Dehydration of formamides

Dehalogenation of l,l,2-trichloro-2,3,3-trifluorocyclobutane, 43,45 Dehydration of formamides with phosphorus oxychloride to isocyanides, 41, 13, 101... 

Phosphorus oxychloride, dehydration of formamides with, 41, 13, 101 removal from reaction of cyanoacetic acid and phosphorus pentachlo-ride, 41,5,7... 

Potassium amide ip conversion of o-acetoacetochloroanilide to 3-acetyk)xindole, 40, 1 Potassium ierf-butoxide, 41, 101 in dehydration of formamides to isocyanides, 41, 101... 

An alternative approach towards the PASP synthesis of isocyanides was developed by Bradley [100,101]. It involved the use of a polymer-supported sul-fonyl chloride in the presence of base to afford the dehydration of formamides (Scheme 21). The formamides required could be easily prepared by reaction of the corresponding amines with a formylated benzotriazole resin. Opti-... 

Isocyanides Phosgene in combination with triethylamine has generally been preferred to phosphoryl chloride and triethylamine for dehydration of formamides to isocyanides (1, 857). However, use of phosphoryl chloride in combination with diisopropylamine can give isocyanides in yields comparable to those obtained with phosgene. Even so this new method can fail with some simple alkyl formamides. 

Among the features of Volume 41 is the smallest-scale synthesis yet published in Organic Syntheses, namely, the preparation of 0.0005 mole of cholestanyl methyl ether by a generally useful methylation procedure that employs diazomethane and fluoboric acid (p. 9). Two preparations of isocyanides by dehydration of formamides are included. One of these, illustrated by cyclohexyl isocyanide (p. 13), is most suitable for aliphatic isocyanides while the other, illustrated by o-tolyl isocyanide (p. 101), is most suitable for aromatic isocyanides. 

Dehydration of formamides. This reagent converts formamides to isocyanides in 75-90% yield. It was developed particularly for use with chiral substrates that racemize readily in the presence of basic reagents. Thus it converts 2 into the isocyanide 3 with no significant racemization. 

Dehydration of formamides to isonitriles.3 This reaction can be effected in high yield at -78° with the combination of triflic anhydride and a tertiary amine. It is effective even in the case of vinyl formamides. 

The dehydration of formamide is conducted in iron catalyst tubes at 380°C to 430°C under reduced pressure. The tubes are filled with Fe or A1 phosphate catalyst that also contains Mg, Ca, Zn or Mn as promoters. The selectivity to HCN is 92% to 95%46. 

Dealkylation of tertiary amines with dibenzoyl peroxide, 44, 74 Decarboxylation, intermolecular, of isocyanates to carbodiimides, 43,32 Decker synthesis of amines, 44, 7t, 75 Dehalogenation of l,l,2-trichloro-2,3,3-trifluorocydobutane, 42,45 Dehydration, of formamides with phosphorus oxychloride to isocy-anides, 41, 13, 101 of 4- 2-hydroxyethyl)piperidine to quinuclidine, 44, 90 Dehydrohalogenation of 2-chloroallyl-amines to propargylamines, 44,55 Delepine reaction, to prepare 2-bromo-allylamine, 43, 6 Deoxyanisoin, 40,16 Deoxybenzoin, 40, IT Deoxypiperoin, 40, IT Deaylamine, 41, 8T... 

A MODEL SYSTEM OXYGEN-AIDED DEHYDRATION OF FORMAMIDES ON a-Sb204-Mo03 MECHANICAL MIXTURES... 

Finally, it should be remembered that isonitriles are not only obtained by substitution processes, but also by alternate routes, which may be of high value. In particular the various techniques for the dehydration of formamides, or the phase transfer version of the classical carbylamine reaction should be noted. ... 

On the basis mainly of results obtained in the oxidation of isobutene to methacrolein, the oxidative dehydrogenation of butene to butadiene and the oxygen-aided dehydration of formamide to nitriles, it was possible to show that oxides present in catalysts are located on a scale reflecting donor-acceptor properties (fig. 5). Some oxides are essentially acceptors (e.g., M0O3, some tellurates) they can potentidly cany active and selective sites, provided they receive spillover oxygen. Others are essentidly donors a-Sb204, in this respect, is typical it produces spillover oxygen but carries no sites active for oxidation. Other oxides have mixed properties. The acceptors are relatively covalent, the donors are more ionic [63,77]. 

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