Isocyanides Ritter reaction

In the laboratory of T.-L. Ho, the total synthesis of the novel marine sesquiterpene (+)-isocyanoallopupukeanane was completed." In the endgame of the synthesis, it was necessary to install the isocyano group onto the tricyclic trisubstituted alkene substrate so that it will occupy the more substituted carbon atom (according to Markovnikov s rule). The Ritter reaction was chosen to form the required carbon-nitrogen bond. The alkene substrate was dissolved in glacial acetic acid and first excess sodium cyanide followed by concentrated sulfuric acid was added at 0 °C. The reaction mixture was stirred at ambient temperature for one day and then was subjected to aqueous work-up. The product A/-alkyl formamide was subsequently dehydrated with tosyl chloride in pyridine to give rise to the desired tertiary isocyanide which indeed was identical with the natural product. 

More important than proton additions are additions of electrophilic carbon by which a new carbon-carbon bond is formed. Carbon-carbon bond formation is a major goal in the synthesis of organic compounds. For instance, from a carboxylic acid chloride an a-oxoimidoyl chloride (70) is prepared Addition of a carbocation to an isocyanide gives a species that is identical to the ion obtained in the Ritter reaction " cf. Section III. 

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