http://www.mdpi.com/journal/molecules/special_issues/bifunctional-catalysis/ Dear Colleagues, Recent advances in green and sustainable science and technology strongly demand powerful and sophisticated catalysts with a tunable multifunction. The design and development of molecular catalysts with a bifunction based on the combination of Lewis acid and Lewis base working in concert is of ongoing interest in organic synthetic chemistry. Since the bifunctional catalysts contain two or more active sites for activation of the electrophiles and nucleophiles, they can efficiently effect a wide range of molecular transformation including C–H, C–C, C–O, or C–N bond formation by dual activation and effective accumulation of reacting substrates on the neighboring active centers in the same molecules. Thus, the rational design of the cooperating ligand that also adjust the balance of the electronic factors in the bifunctional catalysts is crucially important to exploit unprecedented catalyst performance. Prof. Dr. Takao Ikariya Guest Editor {snippet name="submission_info"} http://www.mdpi.com/1420-3049/15/12/8988/ In this review, we describe the development by our research group of highly functionalized heterogeneous Olympic medal metal (gold, silver, and copper) nanoparticle catalysts using hydrotalcite as a support, aimed towards Green and Sustainable Chemistry. Olympic medal metal nanoparticles can cooperate with the basic sites on the hydrotalcite surface, providing unique and high performance catalysis in environmentally-benign organic transformations such as aerobic oxidation of alcohols, lactonization of diols and selective deoxygenation of epoxides and nitro aromatic compounds. http://www.mdpi.com/1420-3049/15/12/8988/ Wed, 08 Dec 2010 00:00:00 CET Molecules 2010-12-08 15 12 Review 8988 9007 1420-3049 Development of Heterogeneous Olympic Medal Metal Nanoparticle Catalysts for Environmentally Benign Molecular Transformations Based on the Surface Properties of Hydrotalcite 2010-12-08 doi: 10.3390/molecules15128988 Kiyotomi Kaneda Takato Mitsudome Tomoo Mizugaki Koichiro Jitsukawa http://www.mdpi.com/1420-3049/15/11/8327/ The synthesis and properties of multifunctional thioureas bearing a variety of functional groups at a position remote from the thiourea moiety are described. A 1,5-disubstituted triazole tether connected with a thiourea and another functional group was synthesized via ruthenium catalyzed Huisgen cycloaddition. We demonstrate the utility of the synthetic thioureas as asymmetric catalysts and probes for the mechanistic elucidation of the course of the Michael reaction of an α,β-unsaturated imide http://www.mdpi.com/1420-3049/15/11/8327/ Mon, 15 Nov 2010 00:00:00 CET Molecules 2010-11-15 15 11 Article 8327 8348 1420-3049 Synthesis and Properties of Chiral Thioureas Bearing an Additional Function at a Remote Position Tethered by a 1,5-Disubstituted Triazole 2010-11-15 doi: 10.3390/molecules15118327 Kiyosei Takasu Takumi Azuma Iderbat Enkhtaivan Yoshiji Takemoto http://www.mdpi.com/1420-3049/15/11/8305/ Organoammonium salts composed of a Brønsted acid and an anilinothiourea promoted the Michael addition of β-keto esters and α,β-unsaturated aldehydes in the presence of primary amines to give functionalized 1,4-dihydropyridines enantioselectively. With the use of the different Brønsted acids such as DFA and HBF4 with the same bifunctional thiourea, both enantiomers of 4-substituted 1,4-dihydropyridine were synthesized from the same starting materials. http://www.mdpi.com/1420-3049/15/11/8305/ Mon, 15 Nov 2010 00:00:00 CET Molecules 2010-11-15 15 11 Article 8305 8326 1420-3049 Catalytic Asymmetric Synthesis of Both Enantiomers of 4‑Substituted 1,4-Dihydropyridines with the Use of Bifunctional Thiourea-Ammonium Salts Bearing Different Counterions 2010-11-15 doi: 10.3390/molecules15118305 Kohzo Yoshida Tsubasa Inokuma Kiyosei Takasu Yoshiji Takemoto http://www.mdpi.com/1420-3049/15/11/7732/ The hydrogenation of 2-methylquinoline with Ir catalysts based on chiral phosphine-phosphites has been investigated. It has been observed that the reaction is very sensitive to the nature of the ligand. Optimization of the catalyst, allowed by the highly modular structure of these phosphine-phosphites, has improved the enantioselectivity of the reaction up to 73% ee. The influence of additives in this reaction has also been investigated. Contrary to the beneficial influence observed in related catalytic systems, iodine has a deleterious effect in the present case. Otherwise, aryl phosphoric acids produce a positive impact on catalyst activity without a decrease on enantioselectivity. http://www.mdpi.com/1420-3049/15/11/7732/ Fri, 29 Oct 2010 00:00:00 CEST Molecules 2010-10-29 15 11 Communication 7732 7741 1420-3049 Application of Phosphine-Phosphite Ligands in the Iridium Catalyzed Enantioselective Hydrogenation of 2-Methylquinoline 2010-10-29 doi: 10.3390/molecules15117732 Miguel Rubio Antonio Pizzano http://www.mdpi.com/1420-3049/15/4/2453/ Chiral amines are one of the ubiquitous functional groups in fine chemical, pharmaceutical and agrochemical products, and the most convenient, economical, and eco-benign synthetic pathway to these amines is direct asymmetric reductive amination (DARA) of prochiral ketones. This paper shows that a wide range of aliphatic ketones can be directly aminated under hydrogenation conditions, affording chiral amines with good to excellent yields and with enantioselectivities up to 96% ee. The catalysis is effected by the cooperative action of a cationic Cp*Ir(III) complex and its phosphate counteranion. http://www.mdpi.com/1420-3049/15/4/2453/ Thu, 08 Apr 2010 00:00:00 CEST Molecules 2010-04-08 15 4 Article 2453 2472 1420-3049 Bifunctional Catalysis: Direct Reductive Amination of Aliphatic Ketones with an Iridium-Phosphate Catalyst 2010-04-08 doi: 10.3390/molecules15042453 Villa-Marcos Li Mulholland Hogan Xiao http://www.mdpi.com/1420-3049/15/4/2070/ The use of bifunctional catalysts in organic synthesis finds inspiration in the selectivity of enzymatic catalysis which arises from the specific interactions between basic and acidic amino acid residues and the substrate itself in order to stabilize developing charges in the transition state. Many enzymes act as bifunctional catalysts using amino acid residues at the active site as Lewis acids and Lewis bases to modify the substrate as required for the given transformation. They bear a clear advantage over non-biological methods for their ability to tackle problems related to the synthesis of enantiopure compounds as chiral building blocks for drugs and agrochemicals. Moreover, enzymatic synthesis may offer the advantage of a clean and green synthetic process in the absence of organic solvents and metal catalysts. In this work the reaction mechanism of norcoclaurine synthase is described. This enzyme catalyzes the Pictet-Spengler condensation of dopamine with 4-hydroxyphenylacetaldehyde (4-HPAA) to yield the benzylisoquinoline alkaloids central precursor, (S)-norcoclaurine. Kinetic and crystallographic data suggest that the reaction mechanism occurs according to a typical bifunctional catalytic process. http://www.mdpi.com/1420-3049/15/4/2070/ Wed, 24 Mar 2010 00:00:00 CET Molecules 2010-03-24 15 4 Review 2070 2078 1420-3049 Norcoclaurine Synthase: Mechanism of an Enantioselective Pictet-Spengler Catalyzing Enzyme 2010-03-24 doi: 10.3390/molecules15042070 Bonamore Barba Botta Boffi Macone http://www.mdpi.com/1420-3049/15/3/1280/ A catalytic asymmetric nitro-Mannich (aza-Henry) reaction with rare earth metal/alkali metal heterobimetallic catalysts is described. A Yb/K heterobimetallic catalyst assembled by an amide-based ligand promoted the asymmetric nitro-Mannich reaction to afford enantioenriched anti-b-nitroamines in up to 86% ee. Facile reduction of the nitro functionality allowed for efficient access to optically active 1,2-diamines. http://www.mdpi.com/1420-3049/15/3/1280/ Thu, 04 Mar 2010 00:00:00 CET Molecules 2010-03-04 15 3 Article 1280 1290 1420-3049 Catalytic Asymmetric Nitro-Mannich Reactions with a Yb/K Heterobimetallic Catalyst 2010-03-04 doi: 10.3390/molecules15031280 Tatsuya Nitabaru Naoya Kumagai Masakatsu Shibasaki http://www.mdpi.com/1420-3049/15/1/532/ Catalytic asymmetric 1,4-addition of β-keto esters to nitroalkenes is described. 2.5 mol % of a homobimetallic Lewis acid/Brønsted base bifunctional Co2-Schiff base complex smoothly promoted the reaction in excellent yield (up to 99%), diastereoselectivity, and enantioselectivity (up to >30:1 dr and 98% ee). Catalyst loading was successfully reduced to 0.1 mol %. Mechanistic studies suggested that intramolecular cooperative functions of the two Co-metal centers are important for high catalytic activity and stereoselectivity. http://www.mdpi.com/1420-3049/15/1/532/ Fri, 22 Jan 2010 00:00:00 CET Molecules 2010-01-22 15 1 Article 532 544 1420-3049 Catalytic Asymmetric 1,4-Additions of β-Keto Esters to Nitroalkenes Promoted by a Bifunctional Homobimetallic Co2-Schiff Base Complex 2010-01-22 doi: 10.3390/molecules15010532 Makoto Furutachi Zhihua Chen Shigeki Matsunaga Masakatsu Shibasaki