A Reagent-Controlled Phospha-Michael Addition Reaction of Nitroalkenes with Bifunctional N-Heterocyclic Phosphine (NHP)-Thioureas

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Bifunctional N-heterocyclic phosphine (NHP)-thioureas have been successfully applied for phospha-Michael addition reaction of nitroalkenes to afford diversely substituted β-nitrodiazaphosphonates. This transformation takes place at room temperature under catalyst-free conditions and exhibits broad functional group tolerance. The key to success in catalyst, additive-free reaction conditions is the suitable hydrogen-bond activation of the nitro group by a Brønsted acid (thiourea), which artfully combined with the highly nucleophilic NHP motif for a synergetic effect. Importantly, this transformation enables a two-step synthesis of pharmaceutically, biologically significant β-amino phosphonic acids. © 2016 American Chemical Society.