Reactivity toward CO of Eight-Membered Palladacycles Derived from the Insertion of Alkenes into the Pd–C Bond of Cyclopalladated Primary Arylalkylamines of Pharmaceutical Interest. Synthesis of Tetrahydrobenzazocinones, Ortho-Functionalized Phenethylamines, Ureas, and an Isocyanate

The ortho-metalated complex [Pd­{C,N-C6H2CH2CH2NH2-2,(OMe)2-4,5}­(μ-Br)]2 (1a) derived from
homoveratrylamine reacts with ethyl acrylate, methyl vinyl ketone,
or 2-norbornene to give the dimeric complex arising from the insertion
of the alkene into the Pd–C bond, [Pd­{C,N-CH­(R)­CH2C6H2CH2CH2NH2-2,(OMe)2-4,5}­(μ-Br)]2 (R = CO2Et (2a1), C­(O)­Me (2a2)) or [Pd­{C,N-CH­(C5H8)­CHC6H2CH2CH2NH2-2,(OMe)2-4,5}­(μ-Br)]2 (2a3). Complexes 2a and the phentermine
homologues 2b react with CO to afford Pd(0) and (1) tetrahydrobenzazocinones,
the heterocycles resulting from CO insertion into the Pd–C
bond and C–N coupling, (2) unnatural amino acid derivatives,
resulting from CO insertion and the reaction of the obtained acyl
complex with the solvent (MeOH), or the product of protonolysis of
the Pd–C bond, depending on the nature of the initial cyclopalladated
compound, or (3) ureas, alone or mixed with an isocyanate, in the
presence of a base. Phentermine derivatives 2b react
with HCl to give a dinuclear palladium complex [PdCl­(μ-Cl)­(L)],
where L is the amine arising from the protonolysis of the Pd–C
bond or the alkyl group resulting from Pd–N bond protonolysis,
depending on the nature of the inserted alkene. The crystal structures
of some palladium complexes and organic compounds have been determined
by X-ray diffraction studies.