New intramolecular cyclization of 2H-benzo[e]-1,2-oxaphosphorinine derivatives—a way to the synthesis of unsymmetrical cage phosphonates

Superelectrophilic Activation of Phosphacoumarins towards Weak Nucleophiles via Brønsted Acid Assisted Brønsted Acid Catalysis

“…With this in mind, we aimed at the synthesis of phosphaflavanoids possessing a hydroxyarene moiety. In contrast to the previously reported procedure [35], various phenols with electron-withdrawing groups reacted in TFA media with the compound 1 to give the desired phosphorus analogues of flavonoids 2d,e and 2l. Isolated yields of the compound 2l were considerably lower compared to the phosphaflavanoids 2d,e, which is in accordance with the stronger electron-withdrawing nature of the formyl group.…”

“…Meanwhile, an acid-assisted acid catalysis, particularly Brønsted acid assisted Brønsted acid catalysis (BBA), has emerged as a useful tool for the design of highly reactive and selective acidic catalysts [33,34]. Earlier, we reported the acid-catalyzed arylation of 2-hydroxybenzo[e] [1,2]oxaphosphinine 2-oxides (phosphacoumarins) with some electronrich phenols [35]. However, this transformation was limited to the most reactive phenols only, other aromatics being inert under the reported conditions (Scheme 1C).…”