Synthesis of Isocyanides
The first isocyanide, allyl isocyanide was prepared in 1859 by the chemist Lieke from the reaction of allyl iodide and silver cyanide. Normally the alkylation of an alkali metal cyanide gives a nitrile, but the silver ion protects the carbon end of the cyanide. Commonly, isocyanides are synthesized by the reaction of primary amines with dichlorocarbene or by dehydration of a formamide with phosphorus oxychloride.
- RNH2 + :CCl2 + 2 NaOH → RNC + 2 NaCl + 2 H2O
- RNHC(O)H + POCl3 → RNC + "PO2Cl" + 2 HCl
The Hofmann isocyanide synthesis is a chemical test for primary amines based on their reaction with potassium hydroxide and chloroform as dichlorocarbene precursors to foul smelling isocyanides.
Another route to isocyanides is by reaction of organolithium compounds with oxazoles and benzoxazoles:
The benzoxazole gets deprotonated at the 2-position by n-butyllithium. The lithium compound is in chemical equilibrium with the 2-isocyanophenolate which can be captured by an electrophile such as an acid chloride. Being an ester the formed isocyanate in the example above behaves uncharacteristically with reportedly a mild cherry smell.
Another synthetic route towards an isocyanide is 1) condensation of an amine with formic acid, yielding a formamide, and 2) dehydrating this formamide. Phosgene (or a synthon or precursor such as diphosgene) can be used in combination with formamide to yield isocyanides.
Read more about this topic: Isocyanide
Famous quotes containing the words synthesis of and/or synthesis:
“If in the opinion of the Tsars authors were to be the servants of the state, in the opinion of the radical critics writers were to be the servants of the masses. The two lines of thought were bound to meet and join forces when at last, in our times, a new kind of regime the synthesis of a Hegelian triad, combined the idea of the masses with the idea of the state.”
—Vladimir Nabokov (1899–1977)
“The new shopping malls make possible the synthesis of all consumer activities, not least of which are shopping, flirting with objects, idle wandering, and all the permutations of these.”
—Jean Baudrillard (b. 1929)