Bis-Guanidinate Aluminum Complexes: Synthesis and Catalytic Application in Three-Component Aminophosphorylation of Aldehydes

We report a series of bis-guanidinate-supported aluminum complexes, LAlMeCl (1), LAlMe(OTf) (2), LAlCl2 (3), and LAlEtCl (4) [L = {(ArNH)(ArN)-C═N–C═(NAr)(NHAr)}; Ar = 2,6-Et2-C6H3], prepared via deprotonation and salt-metathesis strategies and characterized by standard spectroscopic methods and single-crystal XRD analysis. The catalytic performance of complexes 1–4 was investigated in the three-component aminophosphorylation (Kabachnik–Fields type) reaction. Among them, complex 2 displayed superior activity, affording a wide range of α-aminophosphonates in high yields under mild, solvent-free conditions and at low catalyst loadings. Based on literature precedents and the characterization of the key intermediate via mass spectrometric analysis, a plausible catalytic cycle was proposed. These results highlight the potential of bis-guanidinate-supported aluminum triflate complex (2) as an effective and sustainable catalyst for multicomponent C–P and C–N bond-forming reactions.