Sequential Insertion of Alkynes and CO or Isocyanides into the Pd–C Bond of Cyclopalladated Phenylacetamides. Synthesis of Eight-Membered Palladacycles, Benzo[<i>d</i>]azocine-2,4(1<i>H</i>,3<i>H</i>)-diones, and Highly Functionalized Acrylonitrile and Acrylamide Derivatives

The cyclopalladated complexes [Pd­{κ2C,O-C6H4CH2C­(O)­NRR′-2}­(tmeda)]­TfO [R = R′ = H (1a), R = Me, R′ = H (1b), R = R′ = Me (1c)] react with alkynes XCCX′ in 1:3 molar ratio to give the eight-membered palladacycles [Pd­{κ2C,O-C­(X)C­(X′)­C6H4CH2C­(O)­NRR′-2}­(tmeda)]­TfO [R = R′ = H and X = X′ = Ph (2aa), CO2Me (2ab), Et (2ac) or X = Ph, X′ = Me (2ad); R = Me, R′ = H and X = X′ = Ph (2ba), CO2Me (2bb), Et (2bc) or X = Ph, X′ = Me (2bd); R = R′ = Me and X = X′ = Ph (2ca)]. The treatment of complexes 2aa, 2ac, 2ad, 2ba, 2bc, and 2bd with CO at 50 °C affords the corresponding benzo­[d]­azocine-2,4­(1H,3H)-diones (3), which result from the insertion of a molecule of CO into the Pd–C bond and subsequent C–N reductive coupling and formation of (tmedaH)­TfO. The reaction of 2ab with CO in MeOH gives (MeO2C)2CC­(CO2Me)­C6H4CH2C­(O)­NH2-2 (4ab). Complexes 2aa and 2ab react with 1 equiv of R″NC 1:1 to give [Pd­{C­(X)C­(X′)­C6H4CH2C­(O)­NH2-2}­(CNR″)­(tmeda)]­TfO [R″ = t-Bu, X = X′ = Ph (5a), CO2Me (5b); R = Xy, X = X′ = Ph (5a′), CO2Me (5b′)]. While 2aa reacts with 1 equiv of R″NC in refluxing CHCl3 to give a low yield of the compound XyHNC­(O)­C­(Ph)C­(Ph)­C6H4CH2C­(O)­NH2-2 (6a) when R″ = Xy, the complex 2aa, 2ba, or 2ca affords the acrylonitrile derivative NCC­(Ph)C­(Ph)­C6H4CH2C­(O)­NRR′-2 [R = R′ = H (7a), R = Me, R′ = H (7b), R = R′ = Me (7c)] when R″ = t-Bu; alternatively, the latter derivatives can be obtained by refluxing in situ generated solutions of the corresponding cyano complexes [Pd­{C­(Ph)C­(Ph)­C6H4CH2C­(O)­NRR′-2}­(CN)­(tmeda)] in CHCl3. The intermediate cyano complex with R = R′ = H (8) has been isolated and characterized. The reactions of 2aa, 2ba, 2ca, and 2ac with 4 equiv of XyNC give [Pd3(CNXy)6] and mixtures from which the compounds XyNHC­(O)­C­(Ph)C­(Ph)­C6H4CH2CN-2 (9, from 2aa), XyNHC­(O)­C­(Ph)C­(Ph)­C6H4CH2C­(O)­NRR′-2 [R = Me, R′ = H (6b), R = R′ = Me (6c), from 2ba or 2ca, respectively], or [Pd­{C­(NXy)­C­(Et)C­(Et)­C6H4CH2CN-2}­Cl­(CNXy)2] (10, from 2ac) can be isolated. The crystal structures of 2aa·2Et2O, 3aa, 3ac, 8, 9, and 10 have been determined.