Abstract
[2 + 3] cycloaddition of the pyrrolin N-oxide -O+N=CHCH2CH2CMe2 2 with 2-cyanopyridine NC5H4(2-CN) 1a in the presence of PdCl2 at room temperature in acetone gives the ketoimine palladium(II) complex cis-[PdCl2{N(=CCH2CH2C(Me)(2)NH)C(=O)C5H4N}] 3a containing the (E)-N-(5,5-dimethylpyrrolidin-2-ylidene)picolinamide ligand, in good yield (85%). The reaction of 2 with 3-cyanopyridine NC5H4(3-CN) 1b or 4-cyanopyridine NC5H4(4-CN) 1c under the same experimental conditions gives the simple adducts of cyanopyridines trans-[PdCl2{NC5H4(3-CN)}(2)] 4b or trans-[PdCl2{NC5H4(4-CN)}(2)] 4c, respectively. When the cyanopyridines (NC5H3RR2)-R-1 1 (R-1 = 2-CN, R-2 = H 1a; R-1 = 3-CN, R-2 = H 1b; R-1 = 4-CN, R-2 = H 1c; R-1 = 4-CN, R-2 = 2-Cl 1d; R-1 = 3-CN, R-2 = 5-Me 1e) are heated at 100 degrees C for 12 h with 2-butanone oxime (used as a reagent and solvent) in the presence of PdCl2, the 2,4-dipyridyl-1,3,5-triazapentadienate (or bis-imidoylamidinate) palladium(II) complexes [Pd{HN=C(NC5H3R2)NC(NC5H3R2)=NH}(2)] 5 (2-NC5H3, R-2 = H 5a; 3-NC5H3, R-2 = H 5b; 4-NC5H3, R-2 = H 5c; 4-NC5H3, R-2 = 2-Cl 5d; 3-NC5H3, R-2 = 5-Me 5e) are synthesized by one-pot template transformations followed by deprotonation by a base (n-PrNH2). The compounds were characterized by IR, H-1 and C-13 NMR spectroscopies, FAB(+)-MS, elemental analyses and, in the cases of 3a, 5a, 5b and 5d, also by X-ray diffraction analyses. The catalytic activity of complexes 3 and 5 was studied under microwave irradiation for C-C coupling reactions, in the solid phase on a silica gel support, and it was found that complex 3a is the most active one with the maximum TON of 2.0.10(5) and TOF of 1.3.10(4) min(-1) for Suzuki-Miyaura, and TON of 800 and TOF of 27 min(-1) for Heck reactions.