Reactivity of dihydrodiazaphosphinines towards unsaturated substrates: Addition, [5 + 2] cycloaddition and rearrangement processes

Article abstract of DOI:10.1016/S0022-328X(96)06618-1

Treatment of 4-amino-1-azadienes 1 with dichloro (diisopropylamino)phosphane gave 1,2-dihydro-1,3,2-diazaphosphinines 3, which cycloadded in a [5 + 2] fashion to dimethyl acetylenedicarboxylate to furnish bicyclic iminophosphoranes 5. The single addition compound 6 was formed by reaction of 3a with (CO)₅Cr=C(OMe)(C=CPh). Compounds 5 underwent formal 1,7-rearrangement to 7 at room temperature. In turn, 5a reacted with electrophiles (difluorochloroacetic acid and methyl iodide) through the valence isomer 5a′ to give polycyclic structures 13 and 14, which led to 16 by fluoride-induced [4 + 2] cycloreversion. Other reactive electrophilic substrates, like diethyl azodicarboxylate and N-phenyltriazolinedione, led to the oxidized derivative 9 and to the addition product 12 respectively. The X-ray structures of 7a and 12 are discussed.