Nitriles. III. Synthesis of chlorocyanoacetylene and cyanoacetylene, and a novel malononitrile synthesis from chlorocyanoacetylene

Abstract

Pyrolysis of trichloropropionitrile and dichloropropionitrile at 900-1000°under reduced pressure provided a novel synthesis of chlorocyanoacetylene (ca. 80%) and cyanoacetylene (40-60%). Chlorocyanoacetylene reacted with ammonia to give malononitrile in high yields.Cyanoacetylene is a compound of considerable interest, because it has two conjugated triple bonds in the molecule and, perhaps, will find wide application in the synthesis of a variety of heterocyclic compounds. It may also be useful as a monomer in the chemistry of polymers. Although cyanoacetylene has been known for many years, its chemical properties remain uninvestigated, largely owing to lack of a convenient synthesis. The most orthodox method for its synthesis has been recorded by Moureu,1 2 and involves the dehydration of propiolamide with phosphorus pentoxide. Since propiolamide has to be prepared from acetylene by a series of reactions including carbonylation, esterification, and amidation, this approach is far from being practical. Several workers3 thereafter somewhat improved Moureu's method but could not alter its lengthy nature.Recently, several patents claim that cyanoacetylene can be prepared by the dehydration of propargylaldehyde oxime4 or by some gas-phase reactions of acetylene5 or acetonitrile6 with hydrogen cyanide at high temperatures.Chlorocyanoacetylene was first prepared by Kloster-Jensen7 by the reaction of chlorine with lithium cyanoacetylide and its melting point (42-42.5°) and ir and uv spectral data were recorded by the same author.Recently, Bjorvatten8 reported the X-ray crystallographic study of chlorocyanoacetylene with the sample supplied by Kloster-Jensen. However, for lack of a (1) (a) Paper II: N.

Nitriles (Cyanides)

“…*" ĈC^ ( 6 8 ) (18) Pyrolysis of trichloropropionitrile to provide chlorocyanoacetylene [165]. (19) Photochemical cyanation of acetophenone, by acetyl displacement [166].…”