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Aziridines are highly useful compounds as building blocks for the synthesis of important organic compounds. Amino acid synthesis by aziridine ring opening reaction is a good example to the use of aziridines. Although this reaction is studied by many groups, the synthesis of amino phosphonic acids is less explored. In this study, we have carried out the ring opening reaction of aziridinyl phosphonates with a variety of alcohols including the more functional propargylic and allylic alcohols. These reactions provided functionalized α‐amino‐β‐alkoxyphosphonates in 40–91 % yield.

New derivatives of FAM (ferrocenyl aziridinyl methanol) ligands NFAM1-4 (naphthyl ferrocenyl aziridinyl methanol) and CFAM1-4 (cyclohexyl ferrocenyl aziridinyl methanol) were synthesized to form a small ligand library and used as chiral catalysts with AgOAc for the asymmetric synthesis of heteroaryl-substituted pyrrolidines by the 1,3-dipolar cycloaddition (1,3-DC) reaction of azomethine ylides. 2-Thienyl, 2-furyl, 2-, 3-, and 4-pyridyl aldimines were prepared and used with N-methylmaleimide, dimethyl maleate, tert-butyl acrylate, methyl acrylate, and acrylonitrile to form the corresponding heteroaryl-substituted pyrrolidines. 1,3-DC reactions yielded the expected cycloadducts in up to 89% yield and up to 76% ee that could be increased up to 95% ee upon crystallization. New chiral ligands NFAM1-4 and CFAM1-4 were fully characterized, and their absolute stereochemistry was determined by single-crystal X-ray analysis.

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We have prepared a ligand library based on a ferrocenyl aziridinyl methanol core unit (simply called FAM) having a phenyl group, a cyclohexyl group, and a naphthyl group to be used in 1,3-dipolar cycloaddition (1,3-DC) reactions for the synthesis of chiral pyrrolidines. These chiral ligands were used with AgOAc in 1,3-DC reactions taking place between the aryl-substituted azomethine ylides and N-methylmaleimide as the dipolarophile. In each case, the expected aryl-substituted pyrrolidines were obtained in good to excellent yields with acceptable enantioselectivities favoring only the endo product. The chiral catalyst system CFAM4-AgOAc was also used in 1,3-DC reaction with different dipolarophiles such as dimethyl maleate, tert-butyl acrylate, methyl acrylate, trans-chalcone, and vinyl sulfone. In each case, the cycloadducts were obtained in acceptable yields albeit with low ee. Fortunately, it was possible to increase the ee up to >99% upon crystallization.