Regioselectivity of aryl radical attack onto isocyanates and isothiocyanatesElectronic supplementary information (ESI) available. See DOI: 10.1039/c8ob02209g

• Main Authors: Weragoda, Geethika K, Pilkington, Rowan L, Polyzos, Anastasios, O'Hair, Richard A. J
• Format: Journal Article
• Language: English
• Published: 28.11.2018
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/c8ob02209g

The combination of multistage mass spectrometry experiments employing the distonic radical approach together with DFT calculations are used to examine addition of the N -methyl-pyridinium-4-yl radical cation ( γ-NMP ) to iso(thio)cyanates in the gas-phase. The type of products formed depend on the nature of the iso(thio)cyanate: (1) hydrogen atom abstraction occurs for alkyl isocyanates; (2) aryl isocyanates undergo radical- ipso substitution; (3) radical attack occurs at the C&z.dbd;C bond of allyl isocyanate; (4) radical attack occurs at the C&z.dbd;S bond of isothiocyanates to generate S adducts of γ-NMP and isonitriles. DFT calculations provide insight into the reactivity differences of these heterocumulenes towards the electrophilic C-centered γ-distonic radical cations. Translation of these gas phase results to the solution phase were hampered by dominating radical recombination reactions which appear to be favoured over the radical-iso(thio)cyanate reactions. Regioselectivity of attack by the N -methyl-pyridinium-4-yl radical cation onto RN&z.dbd;C&z.dbd;X (X = O and S) depends on R and X.