Dehydration Phosphoryl chloride-Diisopropylamine

Preparation of cyanides.1 An attractive route to cyanides involves as the first step dehydration of alkylformamides with phosgene-tricthylamine (1,857) or phosphoryl chloride-diisopropylamine (13,249) to form isocyanidcs followed by isocyanidc-cyanide rearrangement. This rearrangement traditionally was conducted in the gas phase, but proceeds in almost quantitative yield when carried out by flash pyrolysis at 600°. This route to cyanides is attractive because allyl isocyanides rearrange without allylic rearrangement. Moreover, optically active carboxylic acids can be obtained from optically active amines without raccmization. 

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. 

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