December 2022

The reaction of phosphonates carrying a binaphthyl group with a range of Grignard reagents was complete within two hours at 0 °C to give phosphinates carrying a hydroxybinaphthyl group with high ­efficiency and diastereoselectivity. The resulting phosphinates were further subjected to a substitution reaction with MeMgBr. The reaction at reflux temperature in THF or toluene permitted the formation of P-chirogenic tertiary phosphine oxides with a high enantiomeric ratio. Rare examples of P-chirogenic alkynyl phosphine oxides were also obtained. The sequential one-pot substitution reaction of phosphonates bearing a binaphthyl group with two different Grignard reagents successfully gave the corresponding P-chirogenic phosphine oxides with enantiomeric ratios nearly equal to those of oxides derived from two-step reactions.

Synthesis of several heterocycle-fused λ5-phosphinines through intramolecular cyclization is described. The incorporation of a heteroatom affected their photophysical properties through perturbation of the LUMO level, which is in good contrast to the HOMO-based tuning by the C-4 substituent. The C-3-substituent-based property tuning provides a new guide to designing phosphinine-based fluorophores.