Categories: C-N Bond Formation >
Synthesis of isocyanates
Alkyl isocyanates are prepared in good to excellent yields by treatment of alcohols, thiols and trimethylsilyl ethers with triphenylphosphine/2,3-dichloro-5,6-dicyanobenzoquinone/Bu4NOCN in acetonitrile. This method is highly selective for conversion of primary alcohols to alkyl isocyanates in the presence of secondary and tertiary alcohols, thiols and trimethysilyl ethers.
B. Akhlaghinia, Synthesis, 2005, 1955-1958.
A smooth and efficient oxidation of isonitriles to isocyanates by DMSO as the oxidant is catalyzed by trifluoroacetic anhydride. The process is complete in a few minutes, forming dimethyl sulfide as the only byproduct. The newly formed isocyanates may be used directly or isolated in high purity by solvent evaporation.
H. V. Le, B. Ganem, Org. Lett., 2011, 13, 2584-2585.
A catalytic amount of N-methylimidazole (NMI) accelerated a mild one-pot synthesis of aromatic and aliphatic carbamates via the Lossen rearrangement. Moreover, the utility of arylsulfonyl chloride in combination with NMI minimizes the formation of often-observed hydroxamate-isocyanate dimers.
S. Yoganathan, S. J. Miller, Org. Lett., 2013, 15, 602-605.