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

The cyclopalladated complexes [Pd{kappa C-2,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{kappa C-2,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 degrees 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)(2)C=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 [Pd-3(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.2Et(2)O, 3aa, 3ac, 8, 9, and 10 have been determined.