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12.3.1.5.1.6 Method 6: Reactions of Related Isocyanides with Nitriles

DOI: 10.1055/sos-SD-012-00398

Grimmett, M. R.Science of Synthesis, (200212399.

The reactions in Section 12.3.1.5.1.6 can be extended to involve other isocyanides susceptible to metalation on an α-carbon atom. An example is (4-tolylsulfanyl)methyl isocyanide (164), which forms an even more nucleophilic anion than tosylmethyl isocyanide. It can react with a variety of nitriles to form imidazoles 165 (Scheme 83).[‌297‌] The cyanides are added at 75°C to the monoanions formed from a variety of sulfanylmethyl isocyanides. The customary base treatment uses butyllithium in tetrahydrofuran/hexane. The process is completed by allowing the reaction mixtures to warm up to 0°C followed by quenching with water (Method A). An alternative is to add an equimolar mixture of the isocyanide and the nitrile in tetrahydrofuran to a stirred suspension of potassium tert-butoxide in the same solvent. Addition of water after 15 minutes leads to the 4,5-disubstituted imidazoles in high yields (Method B). Method A is particularly useful for reactions with sterically hindered nitriles. The sulfur substituents of 165 can be removed if necessary by treatment with Raney nickel.[‌297‌]

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