Reactions of Ethyl Phosphites with β-Nitrostyrenes. The Role of Nitrosoalkenes as Intermediates

3-Phenyl-2-substituted-indoles are formed in high yields in the reaction of Ph₂C=C(R)NO₂ (R = H, Me, Ph) with (EtO)₃P at 150 °C while reaction with (EtO)₂PO^-/(EtO)₂P(O)H at room temperature forms the aziridines 1 with R = H, Me, Ph. 2,2-Diphenyl-3-substituted-2H-azirines formed by deoxygenation of the Michael-type adducts are postulated as intermediates. Reactions of PhCH=C(R)NO₂ (R = H, Me, Ph) with (EtO)₃P at 150 °C or (EtO)₂PO^-/(EtO)₂P(O)H at room temperature give products resulting from the addition of the phosphorus nucleophile at the benzylidene carbon atom. Evidence for the formartion of cyclic structures with pentacoordinated phosphorus atoms is presented for the reaction of Ph₂C=C(Me)NO₂ with (EtO)₂PO^-/EtO)₂P(O)H and for PhCH=C(R)NO₂ (R = H, Me, Ph) with (EtO)O₃P. The Michael-type adducts PhCH[P(O)(OEt)₂]CH(R)NO₂ (R = Me, Ph) undergo reaction upon treatment with aqueous base at 80–100 °C followed by acidification to yield the 3-(diethoxyphosphinyl)-2-R-N-hydroxyindoles. 4-(Diethoxyphosphinyl)-3-R-4H-1,2-benzoxazines (13, R = Me, Ph) are formed by reaction with 85% H₂SO₄ of the adducts of PhCH=C(R)NO₂ with (EtO)₂PO^- (R = Me) or (EtO)₃P (R = Ph).