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A more sustainable and highly practicable synthesis of aliphatic isocyanides
- Waibel, K. A., Nickisch, R., Möhl, N., Seim, R., Meier, M. A. R.
- Green chemistry 2020 v.22 no.3 pp. 933-941
- green chemistry, iodine, toxicity
- Synthesis protocols to convert N-formamides into isocyanides using three different dehydration reagents (i.e. p-toluenesulfonyl chloride (p-TsCl), phosphoryl trichloride (POCl₃) and the combination of triphenylphosphane (PPh₃) and iodine) were investigated and optimized, while considering the principles of green chemistry. Comparison of the yield and the E-factors of the different synthesis procedures revealed that, in contrast to the typically applied POCl₃ or phosgene derivatives, p-TsCl was the reagent of choice for non sterically demanding aliphatic mono- or di-N-formamides (yields up to 98% and lowest E-factor 6.45). Apart from a significantly reduced E-factor, p-TsCl is cheap, offers a simplified reaction protocol and work-up, and is less toxic compared to other dehydration reagents. Thus, this procedure offers easier and greener access to aliphatic isocyanide functionalities.