Synthesis and Reactivity of Ortho-Palladated 3-Phenylpropanamides. Insertion of CO, XyNC, and Alkynes into the Pd-C Bond. Synthesis of Seven- and Nine-Membered Palladacycles and Benzazepine- and Benzazonine-Based Heterocycles

Aryl palladium complexes [Pd{C6H4(CH2)(2)C(O)NRR')-2}I(tmeda)] [NRR' = NH2 (1a), NHMe (1b), NMe2 (1c); tmeda = N,N,N',N'-tetramethylethylenediamine] are prepared by oxidative addition of the corresponding 3-(2-iodophenyl)propanamides to Pd(dba)(2) ([Pd-2(dba)(3)]center dot dba; dba = dibenzylideneacetone) in the presence of tmeda. The cationic seven-membered palladacycles [Pd{kappa C-2,O-C6H4(CH2)(2)C(O)NRR')-2}(tmeda)]TfO (2a-c) are obtained by reacting 1a-c with AgTfO. Neutral amidate complexes of the type [Pd{kappa C-2,N-C6H4(CH2)(2)C(O)NR)-2}(tmeda)] [R = H (3a), Me (3b)] are obtained upon deprotonation of the amide function in 1a or 1b with (KOBu)-Bu-t. The reaction of la with CO at room temperature affords the stable acyl derivative [Pd{C(O)C6H4(CH2)(2)C(O)NH2-2}I(tmeda)] (4), while 2a gives Pd, (tmedaH)TfO, and 4,5-dihydro-2H-benzo[c]azepine-1,3-dione (5a). Compound 5a can also be obtained in high yield by treating the amidate complex 3a with CO, while a low yield of 2-methyl-4,5-dihydro-2H-benzo[c]azepine-1,3-dione (5b) was obtained from 3b under the same conditions. Complexes 1a-c react with 3 equiv of XyNC to give trans-[Pd{C(=NXy)C6H4(CH2)(2)C(O)NRR'-2}I(CNXy)(2)] [NRR' = NH2 (6a), NHMe (6b), NMe2 (6c)]. By refluxing a CHCl3 solution of 6a or 1a and XyNC in 1:1 molar ratio, mixtures of 1-(2,6-dimethylphenylimino)-1,2,4,5-tetrahydrobenzo[c]azepin-3-one (7a) and 2-(2-cyanoethyl)-N-(2,6-dimethylphenyl)benzamide (8a) are obtained. Complexes 2a-c react with alkynes in 1:1 molar ratio to give nine-membered palladacycles of the type [Pd{kappa C-2,O-C(X)=C(X)C6H4(CH2)(2)C(O)NRR'-2}(tmeda)]TfO [NRR' = NH2, X = Ph (9a), (C6H4Bu)-Bu-n-4 (10a), C6H4Br-4 (11a), CO2Me (12a); NRR' = NHMe, X = Ph (9b); NRR' = NMe2, X = Ph (9c)]. The reaction of 2a with an excess of 3-hexyne gives the complex [Pd{eta(3)-C6H4(C4Et4)(CH2)(2)C(O)NH2}(tmeda)]TfO (13), containing a spirocyclic ligand coordinated to Pd through a eta(3)-allylic bond. The derivatives 9a, 10a and 11a react with CO at 50 degrees C in CHCl3 to give colloidal Pd, (tmedaH)TfO, and the corresponding 6,7-disubstituted 1,2-dihydro-4H-benzo[e]azonine-3,5-diones (14, 15, 16), which result from a CO insertion/C-N reductive coupling sequence.