Asymmetric Organocatalyzed Phospha-Michael Addition for the Direct Synthesis of Biologically Active Chromenylphosphonates,*   Marqués-López, E.; Sonsona, I. G.; Garcés-Marín, M.; Gimeno, M. C.; Herrera, R. P. Adv. Synth. Catal. 2023, 365. DOI: 10.1002/adsc.202300563. *A previous version of this manuscript has been deposited on a preprint server (DOI: 10.26434/chemrxiv-2023-dpm20).

Abstract. The potential of phosphites as nucleophiles for the asymmetric synthesis of chiral chromene derivatives has been overlooked in the literature. Herein, we report a promising approach via asymmetric organocatalyzed phospha-Michael addition to iminochromenes, using a bifunctional squaramide, which gives access to chromenylphosphonates, an interesting family of bioactive compounds. Our optimized protocol provides very good reactivity, affording yields of up to 95% and with chiral products exhibiting an enantiomeric excess of up to 98%.

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