Synthesis of Bench‐stable Polycyclic Organophosphorus Heterocycles via Staudinger‐type Annulations of ortho‐Azidophenols

Abstract

AbstractThe formation of a five‐ or six‐membered ring is known to stabilize unstable molecular structures such as hemiacetals. This idea can also be extended to stabilize other high‐coordinated p‐block element species. Herein, we synthesized two novel polycyclic organophosphorus heterocycles via Staudinger‐type annulations. Reactions of either ortho‐phosphinoarenesulfonyl fluorides 1 or ortho‐phosphinobenzoic acid methyl esters 4 with ortho‐azidophenols 2 gave rise to penta‐coordinated P(V) heterocycles, benzo‐benzo‐1,2,3‐thiazaphospholo‐1,3,2‐oxazaphosphole (B‐B‐TAP‐OAP) 3 and benzo‐benzo‐1,2‐azaphospholo‐1,3,2‐oxazaphosphol‐12‐one (B‐B‐AP‐OAP) 5 in satisfactory yields. It is remarkable that heterocycles 3 and 5 are both bench‐stable and exhibit considerable stability in a 10 % aqueous tetrahydrofuran solution. Preliminary computational studies disclosed that the formation of nitrogen gas is the key driving force for the annulations. In addition, the formation of a strong Si−F bond is another contributor to the annulation of 1 and 2.