10.1021/ol800921n.s001 Stephen P. Marsden Stephen P. Marsden Alison E. McGonagle Alison E. McGonagle Ben McKeever-Abbas Ben McKeever-Abbas Catalytic aza-Wittig Cyclizations for Heteroaromatic Synthesis American Chemical Society 2008 iminophosphorane Catalytic organophosphorus component Cyclization involvement benzoxazole azole reaction efficiency cyclization azine heterocycle synthesis formation mol phenanthridine phosphine oxide Heteroaromatic Synthesis spectroscopy catalyst loadings 2008-06-19 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Catalytic_aza_Wittig_Cyclizations_for_Heteroaromatic_Synthesis/2933194 The first examples of heterocycle synthesis by iminophosphorane formation/intramolecular aza-Wittig cyclizations that are catalytic in the organophosphorus component are reported. The reaction has been demonstrated in the synthesis of both azine (phenanthridine) and azole (benzoxazole) heterocycles. Catalyst loadings down to 1 mol % have been used with little or no loss in reaction efficiency. The intimate involvement of the phosphine oxide in the catalytic cycle has been verified by in situ infrared spectroscopy.