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DOI: 10.1055/sos-SD-019-00308

Suginome, M.; Ito, Y.Science of Synthesis, (200419453.

Isocyanates 16 are transformed into isocyanides 17 by deoxygenation with appropriate reagents (Scheme 11). tert-Phosphites such as triethyl phosphite serve as the reagent for deoxygenation above 150°C.[‌31‌] Ethyl, hexyl, and cyclohexyl isocyanides are synthesized from the corresponding isocyanates in 3457% yields. Aromatic isocyanates fail to afford the corresponding isocyanides in high yields. Comparison of several phosphites revealed that triethyl and tributyl phosphite are effective, whereas trimethyl and triphenyl phosphite are poor deoxygenation reagents. A more-elaborated phosphorus reagent has been developed:[‌32‌] the phosphine-based reagent 18 is prepared from dichloro(phenyl)phosphine or bis(diethylamino)(phenyl)phosphine with 2-(methylamino)ethanol in 41 and 83% yield, respectively. The reagent 18 converts phenyl isocyanate into phenyl isocyanide in a 57% yield below 36°C. Likewise, some aryl isocyanides are conveniently obtained from the corresponding isothiocyanates in moderate to good yields using 18. Deoxygenation of cyclohexyl isocyanate needs a reaction temperature as high as 80°C, giving cyclohexyl isocyanide in 74% yield with recovered isocyanate.

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