GRAPHICAL ABSTRACT
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Abstract
1H-1,3-Azaphospholes and their benzo-fused derivatives are a particular class of aromatically stabilized σ2P heterocycles1,2 that differ from the well-known phosphabenzenes1a,3 and other types of azaphospholes1c by their increased π-density at phosphorus. This is caused by delocalization of the σ3N lone pair in the five-membered ring, the position of N in conjugation to phosphorus, the lack of P-N bonds, and the absence of electron-withdrawing σ2N atoms, and leads to a specific reactivity pattern, in many aspects different from that of other P = C compounds (Figure 1). We present a short overview on new routes to mono- and bidentate benzazaphospholes, substitution reactions at P, C2, and N and also on solvent/additive-dependent addition reactions of tBuLi, which provide access to sterically demanding and P-basic phosphine ligands. In addition, the application potential of bap-W(CO)5/Ag(+) initiators for ring-opening-polymerization of 3-5 membered cyclic ethers and of dihydro-benzazaphosphol-2-carboxylate Ni catalysts for the oligomerization of ethylene is shown.