Addition Reactions of a Phosphorus Triamide to Nitrosoarenes and Acylpyridines

Abstract

Tricoordinate phosphorus compounds react with a wide variety of double bonds through addition reactions. The dipolar and cyclic products formed are important intermediates in organophosphorus chemistry. We investigated the reactivity between phosphorus triamide 1 and nitrosoarenes and 2-acylpyridines. For sterically congested substrates, the formation of σ5,λ5-phosphorus products is observed. DFT calculations indicate this product is formed through a concerted [4 + 1] mechanism. For less sterically congested substrates, products are observed arising from cleavage of the N = O or C = O bond with formation of a terminal P = O bond and aryl nitrene or carbene migration into a P–N bond of the phosphorus triamide core. DFT calculations are consistent with an initial [2 + 1] addition to phosphorus followed by formal carbene/nitrene migration in these cases.