Reaction of an anthracene-based cyclic phosphonate ester with trimethylsilyl bromide unexpectedly generating two phosphonates: syntheses, crystal structures and fluorescent properties

Abstract

Reaction of the cyclic phosphonate ester of anthracen-9-yl(5,5-dimethyl-2-oxo-2λ⁵-1,3,2-dioxaphosphinan-2-yl)-methanol (1) with TMSBr unexpectedly generated phosphonates 2-(10-bromoanthracen-9-ylmethyl)-5,5-dimethyl-2λ⁵-1,3,2-dioxa-phosphinan-2-one (2) and (10-bromoanthrancen-9-yl)methyl-phosphonate mono(3-bromo-2,2′-dimethylpropyl) ester (3) through a series of bond cleavages and formations. Compound 3 could transform into 2 in CH₃OH–H₂O solution, but it is stable in dry CH₃CN. The structures of 1–3 have been characterized by IR spectra, ¹H NMR spectra, and crystal structures. In contrast to 1, the dioxaphosphorinane ring is open in 3, but not changed in 2. In addition, both 2 and 3 contain a bromine-substituted anthracene group, and have no hydroxyl group as that in 1. For compounds 1–3, their crystal structures and fluorescent properties in CH₂Cl₂ solution and in the solid state have been studied.