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A variety of neutral ruthenium−carbene complexes RuCl2(carbene)(arene) 1 (carbene = C(NR)C6H4(NR), R = Me (a), Et (b); arene = p-Me-C6H4-iPr (1), C6H3Me3 (2), C6Me6 (3)) have been prepared by reaction of [RuCl2(arene)]2 precursors with the enetetraamines (RN)C6H4(RN)CC(NR)C6H4(NR) I (R = Me) and II (R = Et). RuC(NCH2Ph)CH2CH2(NCH2Ph)Cl2(p-cymene) (4) was prepared similarly, whereas the reaction of [RuCl2(cycloocta-1,5-diene)] n with I led to the formation of the 16-electron neutral complex RuCl2[C(NMe)C6H4(NMe)]3 (6). One of them (3a) was transformed into the dihydride derivative RuH2(C(NMe)C6H4NMe)(C6Me6) (5). The cyclic voltammograms of derivatives 1−3 show that they are oxidized in the range E1/2 = 1.03−1.31 V vs SCE and are more electrophilic than the isoelectronic RuCl2(PR3)(arene) complexes. Derivatives 1a, 3a, and 3b act as efficient catalyst precursors for the electrophilic activation of the C⋮C bond of (Z)-3-methylpent-2-en-4-yn-1-ol to afford 2,3-dimethylfuran in good yield via intramolecular cyclization.

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A number of novel benzimidazolium salts having aryl substituents such as N-phenyl, 4-chlorophenyl and various alkyl substituents were synthesized. Their microwave-assisted catalytic activities were evaluated in Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions using a catalytic system consisting of Pd(OAc) 2 /K 2 CO 3 in DMF/H 2 O under mild reaction conditions with consistent high yields, except those of 2-bromopyridine.

A mixture of benzimidazole salts (2-7), Pd(OAc) 2 and K 2 CO 3 in DMF-H 2 O catalyzes the Suzuki-Miyaura cross-coupling reactions promoted by microwave irradiation resulting in high yield within a short time. In particular, the yield of the Suzuki-Miyaura reactions with aryl bromides was found to be nearly quantitative. The synthesized benzimidazole salts (2-7) were identified by 1 H-13 C, NMR, IR spectroscopic methods and microanalysis. The molecular structure of 1 was determined by X-ray crystallography. The antibacterial and antifungal activities of the novel benzimidazole derivatives (1-7) were also tested against standard strains.

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Amino acid and peptide conjugates of quinine were synthesized using microwave irradiation in 52-95% yields using benzotriazole methodology. The majority of these conjugates retain in vitro antimalarial activity with IC50 values below 100 nm, similar to quinine.

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