Use of dilithio-tosylmethyl isocyanide in the synthesis of oxazoles and imidazoles

Dilithio-tosylmethyl isocyanide ($\text{2}$) reacts with the carbonyl of unsaturated esters to form oxazoles, unlike tosylmethyl isocyano monoanion which gives pyrroles by reaction with the conjugated carbon-carbon double bonds. Reaction of $\text{2}$ with carbon-nitrogen multiple bonds leads to imidazoles, an example of which is the one-step synthesis of imidazo5,1-a]isoquinoline from isoquinoline. From $\text{2}$ and pyridine-N-oxide or pyridazine-N-oxide unsaturated ring opened products are obtained.