三宅 由寛

Reactions of arylacetic acids bearing an amino group at the para-position in the benzene ring with alkenes in the presence of a catalytic amount of transition metal polypyridyl complexes as photocatalysts under visible light illumination proceed smoothly to give the corresponding benzylated products via oxidative decarboxylation in good to high yields.

Novel mono- and dimolybdenum-dinitrogen complexes bearing an arsenic-containing ANA-type pincer ligand are prepared and characterized by X-ray analyses. These complexes afford a stoichiometric amount of ammonia by treatment with sulfuric acid at room temperature.

Visible-light-mediated direct sp3 C?H amination of benzocyclic amines via a-aminoalkyl radicals by using photoredox catalysts is described here. The obtained N,N-acetals were also successfully applied for carboncarbon bond forming reactions with carbon nucleophiles. The procedure is suitable for a late-stage modification of C?H bonds to C?C bonds.

Although stoichiometric transformations using transition metal-N-2 complexes have been well investigated towards the goal of nitrogen fixation under mild reaction conditions, only a few examples of the catalytic transformations of N-2 using transition metal-N-2 complexes as catalysts have been reported. In almost all the catalytic systems, the use of Mo is essential to realize the catalytic transformation of N-2, where Mo-N-2 complexes are considered to work as effective catalysts. Here we show the first successful example of the Fe-catalysed transformation of N-2 into N(SiMe3)(3) under ambient conditions, in which iron complexes such as iron pentacarbonyl [Fe(CO)(5)] and ferrocenes have been found to work as effective catalysts. A plausible reaction pathway is proposed, where Fe(II)-N-2 complex bearing two Me3Si groups as ancillary ligands has an important role as a key reactive intermediate, with the aid of density-functional-theory calculations.

Novel dinitrogen-bridged dimolybdenum complexes bearing unsymmetric PNP-type pincer ligands are prepared and characterized by X-ray analysis. A molybdenum-dinitrogen complex bearing 2-(di-1-adamantylphosphino)methyl-6-(di-tert-butylphosphino)methylpyridine has been found to work as an effective catalyst toward the formation of ammonia from molecular dinitrogen under ambient conditions.

The reaction of the monophosphido-bridged diruthenium(III) complex [Cp*RuCl(mu-PMe2)(mu-Cl)RuClCp*] with sodium hydrogen sulfide affords the hybrid phosphido- and hydrosulfido-bridged diruthenium(III) complex [Cp*RuCl(mu-PMe2)(mu-SH)RuClCp*]. The hydrosulfido-bridged diruthenium(III) complex can be further converted into the corresponding sulfido-bridged multinuclear ruthenium(III) complex via deprotonation of the hydrosulfido ligand. The hydrosulfido-bridged diruthenium(III) complex also reacts with bases to afford a coordinatively unsaturated diruthenium(III) complex, where insertion of terminal alkynes further occurs to form phosphido-bridged diruthenium(III) complexes bearing ruthenathiacyclobutene moieties.

Novel thiolate-bridged diiron complexes bearing diazenido and diazene ligands in a side-on manner have been prepared and characterized by X-ray analysis. These sulfur-bridged diiron complexes work as effective catalysts toward the reduction of hydrazines into amines and ammonia via a sequential process of protonation and reduction on the sulfur-bridged diiron skeleton, as is likely observed at the active site of nitrogenase.

The enantioselective propargylic alkylation of propargylic alcohols with beta-ketoesters in the presence of a thiolate-bridged diruthenium complex and a copper complex as co-catalyst affords the corresponding propargylic alkylated products in excellent yields as a mixture of two diastereoisomers with high enantioselectivity (up to 95?% enantiomeric excess (ee)). The findings reported herein not only open up a new type of enantioselective propargylic substitution reaction, but also a new aspect of cooperative catalytic reactions using distinct transition metals to realize a useful transformation that cannot be achieved by a single catalyst.

Novel molybdenum- and tungsten dinitrogen complexes bearing PNP-type pincer ligands are prepared and characterized by X-ray analysis. Reactions of these molybdenum- and tungsten-dinitrogen complexes with an excess amount of sulfuric acid in THF at room temperature afford ammonia and hydrazine in good yields.

Recent progress in catalytic reactions via copper-acetylide complexes as key intermediates is reviewed from the viewpoint of organic synthesis. A variety of novel catalytic reactions such as cross-coupling reactions, addition reactions, and cycloaddition reactions using copper-acetylide complexes as carbon sources have been developed. Copper complexes bearing an optically active ligand promote various asymmetric transformations such as propargylic substitution reactions of propargylic esters and ring-opening reactions of ethynyl epoxides, where copper-allenylidene complexes work as key and common intermediates.

A series of heterobimetallic complexes consisting of group IV metallocenyl diphosphines and Ru were synthesized and structurally characterized. Most of them work as catalysts toward propargylic substitution reaction of 1,1-diphenyl-2-propyn-1-ol (4) with EtOH. The stoichiometric reactions of the heterobimetallic complexes [MCl(2)(mu-eta(5):eta(1)-C(5)H(4)PEt(2))(2)RuClCp*] (M = Zr, Hf) with 4 and NaBAr(4)(F) afforded key reactive intermediate allenylidene complexes [MCl(2)(mu-eta(5):eta(1)-C(5)H(4)PEt(2))(2)RuCp*(=C=C=CPh(2))]BAr(4)(F), whose molecular structures were confirmed by X-ray analyses. A plausible reaction pathway for the catalytic reaction is proposed where group IV metal chloride and Ru moieties work cooperatively.

The enantioselective propargylic amination of propargylic pentafluorobenzoates bearing an alkyl group at the propargylic position with amines in the presence of catalytic amounts of a copper complex and an optically active diphosphine such as BINAP has been found to give the corresponding propargylic amines in good yields with high enantioselectivity.

The enantioselective propargylic alkylation of propargylic alcohols bearing an internal alkyne moiety with aldehydes in the presence of a metal salt as the Lewis acid and an optically active secondary amine as the co-catalyst has been found to give the corresponding propargylic alkylated products in high yields as a mixture of two diastereoisomers with high enantioselectivity.

A series of heterobimetallic complexes, including [(MMe)-Me-1(mu-eta(1)-C5H4PEt2)(2)(MCp)-Cp-2*] (5a, M-1 = Zr, M-2 = Ru; 5b, M-1 = Hf, M-2 = Ru; 5c, M-1 = Zr, = Fe) have been prepared and characterized by X-ray analyses. Dehydrogenation of Me2NH center dot BH3 takes place in the presence of a catalytic amount of these heterobimetallic complexes. Studies on the reaction pathway of the catalytic dehydrogenation of Me2NH center dot BH3 lead us to propose a catalytic cycle where two metal centers cooperatively participate in the catalysis. Here, heterobimetallic hydride species serve as key reaction intermediates.

A molybdenum dinitrogen complex bearing two ancillary ferrocenyldiphosphine ligands, trans-[Mo (N-2)(2)(depf)(2)] (depf = 1,1'-bis(diethylphosphino)ferrocene), catalyzes the conversion of molecular dinitrogen (N-2) into silylamine (N(SiMe3)(3)), which can be readily converted into NH3 by acid treatment. The conversion has been achieved in the presence of Me3SiCl and Na at room temperature with a turnover number (TON) of 226 for the N(SiMe3)(3) generation for 200 h. This TON is significantly improved relative to those ever reported by Hidai's group for mononuclear molybdenum complexes having monophosphine coligands [J. Am. Chem. Soc. 1989, 111, 1939]. Density functional theory (DFT) calculations have been performed to figure out the mechanism of the catalytic N-2 conversion. On the basis of some pieces of experimental information, SiMe3 radical is assumed to serve as an active species in the catalytic cycle. Calculated results also support that SiMe3 radical is capable of working as an active species. The formation of five-coordinate intermediates, in which one of the N-2 ligands or one of the Mo P bonds is dissociated, is essential in an early stage of the N-2 conversion. The SiMe3 addition to a "hydrazido(2-)" intermediate having the NN(SiMe3)(2) group will give a "hydrazido(1-)" intermediate having the (Me3Si)NN(SiMe3)(2) group rather than a pair of a nitrido ( N) intermediate and N(SiMe3)(3). The N(SiMe3)(3) generation would not occur at the Mo center but proceed after the (Me3Si)NN(SiMe3)(2) group is released from the Mo center. The flexibility of the Mo P bond between Mo and depf would play a vital role in the high catalysis of the Mo-Fe complex.

The synthesis of transition metal-dinitrogen complexes and the stoichiometric transformation of their coordinated dinitrogen into ammonia and hydrazine have been the subject of considerable research, with a view to achieving nitrogen fixation under ambient conditions. Since a single example in 2003, no examples have been reported of the catalytic conversion of dinitrogen into ammonia under ambient conditions. The dimolybdenum-dinitrogen complex bearing PNP pincer ligands was found to work as an effective catalyst for the formation of ammonia from dinitrogen, with 23 equiv. of ammonia being produced with the catalyst (12 equiv. of ammonia are produced based on the molybdenum atom of the catalyst). This is another successful example of the catalytic and direct conversion of dinitrogen into ammonia under ambient reaction conditions. We believe that the results described in this Article provide valuable information with which to develop a more effective nitrogen-fixation system under mild reaction conditions.

The enantioselective propargylic alkylation of propargylic esters with aldehydes in the presence of a copper complex and an optically active secondary amine as cocatalysts has been found to give the corresponding propargylic alkylated products in good yields as a mixture of two diastereoisomers with a high enantioselectivity.

Novel thiolate-bridged dinuclear ruthenium complexes bearing a phosphine ligand, [Cp*Ru{PhP-(C6H4-o-S)(2)}RuCp*](OTf)(2), [CpRu{PhP(C6H4-o-S)(2)}RuCp*(OH2)](OTf)(2), and [Cp*Fe{PhP(C6H4-o-S)(2)}RuCp*](OTf)(2), are prepared and characterized by X-ray analysis. These dinuclear complexes work as effective catalysts toward propargylic reduction of propargylic alcohols with 2-propanol via allenylidene complexes as key intermediates to give the corresponding alkynes in good to high yields.

The reaction of [Cp*Ru(mu(3)-CI)](4) with ArSK (ArS = 2,6-(Me(3)Si)(2)C(6)H(3)S) gives the mononuclear ruthenium complex with pi-arenethiolate ligand [Cp*Ru(eta(5)-SAr)] via [Cp*Ru(mu-SArk](2.) Further reactions of [Cp*Ru(eta(5)-SAr)] with HCI and [Cp*Ru(mu(3)-CI)](4) give the corresponding monoruthenium complex [Cp*Ru(eta(6)-HSAr)]CI and diruthenium complex [Cp*Ru(mu-eta(5):eta(1)-SAr)RuCICp*] in high yields, respectively.

The scope and limitations of the copper-catalyzed propargylic amination of various propargylic esters with amines are presented, where optically active diphosphines such as Cl-MeO-BIPHEP and BINAP work as good chiral ligands. A variety of secondary amines are available as nucleophiles for this catalytic reaction to give the corresponding propargylic amines with a high enantioselectivity. The results of some stoichiometric and catalytic reactions indicate that the catalytic amination proceeds via copper-allenylidene complexes formed in situ, where the attack of amines to the electrophilic gamma-carbon atom in the allenylidene complex is an important step for the stereoselection. Investigation of the relative rate constants for the reaction of several para-substituted propargylic acetates with N-methylanilines reveals that the formation of the copper-allenylidene complexes is involved in the rate-determining step. The result of the density functional theory calculation on a model reaction also supports the proposed reaction pathway involving copper-allenylidene complexes as key intermediates. The catalytic procedure presented here provides a versatile and direct method for the preparation of a variety of chiral propargylic amines.

Ruthenium-catalyzed enantioselective [3+3] cycloaddition of propargylic alcohols with 2-naphthols affords the corresponding cycloaddition products in moderate to good yields with a high enantioselectivity (up to 99% ee). This cycloaddition proceeds via stepwise reactions of propargylation and intramolecular cyclization, where ruthenium-allenylidene and -vinylidene complexes work as reactive intermediates, respectively.

Heterotrinuclear Fe(II)-Cu(II)-Fe(II) complexes [Cu(FcTropOMe)(2)(H(2)O)(2)](OTf)(2) (FcTropOMe = 5-ferrocenyl-2-methoxytropone) (1), [Cu(FcTropNEt(2))(2)](OTf)(2) (FcTropNEt(2) =2-(N, N-diethylamino)5- ferrocenyltropone) (2) and [Cu(FcTropNEt)(2)] (FcTropNEt = 2-(N-ethylamino)-5-ferrocenyl-troponate) (3) were synthesized. In addition, a hexa. uorophosphate salt of heterotrinuclear Fe(III)-Cu(II)-Fe(III) complex [Cu(FcTropNEt)(2)](2+) (3(2+)) was successfully obtained as single crystals by electrochemical oxidation of 3. By comparing the X-ray structures and absorption spectra of dicationic complexes 1 and 2, the 2-(diethylamino) tropone ligand was found to induce a greater intramolecular charge transfer (CT) from ferrocenyl to tropone-Cu(II) moieties than the 2-methoxytropone ligand. On the other hand, 3(2+) showed a broad CT band in the near-infrared (NIR) region similar to 2, which can be assigned to a transition from troponato-Cu(II) to ferrocenium moieties. As for the magnetic properties of 3(2+)(PF6-)2, measurements of temperature dependence of magnetic susceptibility and ESR on the solid state and in solution revealed the presence of a strong ferromagnetic interaction (J(Fe-Cu) = + 12.0 cm(-1)) between the low spin Fe(III) ion with S = 1/2 and Cu(II) ion with S = 1/2 despite a long distance pathway via the aminotroponato and cyclopentadienyl moieties. DFT calculations supported this intramolecular ferromagnetism, which is induced by a spin polarization mechanism through the pi-spacers.

Tungsten- and molybdenum-dinitrogen complexes bearing bis(dialkylphosphinobenzene)chromiums have been prepared and characterized by X-ray crystallography. Reactions of these dinitrogen complexes with an excess amount of sulfuric acid in methanol at room temperature give ammonia in good yields. Stoichiometric reactions of some dinitrogen complexes with 2 equiv of trifluoromethanesulfonic acid afford the corresponding hydrazido complexes, which may be considered to be one of the reactive intermediates.

We have designed and prepared novel diphosphine ligands bearing an OS(tpy)(2)(2+) moiety as a light-harvesting unit and have found that these diphosphine ligands coordinate to the rhodium atom in a bidentate manner. The rhodium complexes including diphosphine ligands bearing an OS(tpy)(2)(2+) moiety have been revealed to work as an effective photocatalyst for the production of dihydrogen.

Tungsten- and molybdenum-dinitrogen complexes bearing 1, 1'-bis(diethylphosphino)ruthenocene (depr) or 1,1'-bis(dimethylphosphino)ruthenocene (dmpr) have been prepared and characterized spectroscopically. Reactions of tungsten- and molybdenum- dinitrogen complexes bearing ruthenocenyldiphosphines with an excess amount of sulfuric acid in methanol at room temperature give ammonia in good yields.

Ruthenium-catalyzed enantioselective cyclization of propargylic alcohols bearing a thiophene moiety affords the corresponding propargylated thiophenes in good to high yields with a high enantioselectivity (up to 97% ee). This catalytic reaction is proposed to proceed via chiral ruthenium-allenylidene complexes as key intermediates.

Our recent studies on catalytic reactions via ruthenium-allenylidene complexes are reviewed from the viewpoint of organic synthesis. Thiolate-bridged diruthenium complexes work as efficient catalysts to promote a variety of novel organic transformations, especially propargylic substituion reactions, via allenylidene complexes as key intermediates. The asymmetric version of these reactions is also described together with some mononuclear ruthenium complex-catalyzed related reactions by other groups.

Thiolato-bridged dibromo- and diiododiruthenium complexes [{Cp*RuX(mu-SR)}(2)] (X = Br, I; R = Me, (i)Pr) have been prepared and characterized by X-ray analysis. Examination of their catalytic activity in propargylic substitution reactions of 1-phenyl-2-propyn-1-ol with some nucleophiles has revealed that the complexes [{Cp*RuX(mu-S(i)Pr)}(2)] (X = Br, 1) work as catalysts but less effectively in comparison with the well-investigated dichloride analogue [{Cp*RuCl(mu-S(i)Pr)}(2)].

The reaction pathways of two types of the carbon-carbon bond-forming reactions catalyzed by thiolate-bridged diruthenium complexes have been investigated by density-functional-theory calculations. It is clarified that both carbon-carbon bond-forming reactions proceed through a ruthenium-allenylidene complex as a common reactive intermediate. The attack of it electrons on propene or the vinyl alcohol on the ruthenium-allenylidene complex is the first step of the reaction pathways. The reaction pathways are different after the attack of nucleophiles on the ruthenium-alkynyl complex. In the reaction with propene, the carbon-carbon bond-forming reaction proceeds through a stepwise process, whereas in the reaction with vinyl alcohol, it proceeds through a concerted process. The interactions between the ruthenium-allenylidene complex and propene or vinyl alcohol have been investigated by applying a simple way of looking at orbital interactions.

The ruthenium-catalyzed oxypropargylation of alkenes with propargylic alcohols and simple alcohols has been found via ruthenium-allenylidene complexes as key intermediates. As a synthetic application, an intramolecular cyclization using this method has been developed to give the corresponding anti-1-alkoxy-3-ethynylindanes in high to excellent yields with a high diastereoselectivity.

Ruthenium-catalyzed enantioselective propargylation of 1-(triisopropylsilyl)-1H-indoles with propargylic alcohols gives the corresponding beta-propargylated indoles in good yields with high enantioselectivity. Reactions with 1-(1-naphthyl)prop-2-yn-l-ol achieve the highest enantioselectivity (up to 95% ee).

Reactions of the monophosphido-bridged diruthenium(III) complexes [Cp*RuCl(mu-PR2)(mu-Cl)RuClCp*] with a variety of (alkylthio)trimethylsilanes afford the hybrid phosphido- and thiolato-bridged diruthenium complexes [Cp*RuCl(mu-PR2)(mu-SR')RuClCp*]. Although some newly prepared hybrid diruthenium complexes are found to work as catalysts toward propargylic substitution reactions of propargylic alcohols with nucleophiles, their catalytic activity is lower than that of the methanethiolato-bridged diruthenium complex.

Novel tungsten- and molybdenum -dinitrogen complexes bearing 1,1'-bis(diethylphosphino)ferrocenes as auxiliary ligands have been prepared and characterized crystallographically. Reactions of these complexes with an excess amount of sulfuric acid in methanol at room temperature yield ammonia in good yields. This result is in sharp contrast to the previous result that protonolysis of tungsten- and molybdenum -dinitrogen complexes bearing conventional diphosphines such as 1,2-bis(diphenylphosphino)ethane does not produce ammonia. Reactions of the dinitrogen complexes with 2 equiv of trifluoromethanesulfonic acid give the corresponding hydrazido complexes as intermediates. Molecular structures of these hydrazido complexes have been determined by X-ray analysis.

Reactions of a chloride-bridged diruthenium (III) complex with (dialkylphosphino)trimethylsilans afford novel monophosphido-bridged diruthenium complexes, which are further transformed into the corresponding cationic complexes by treatment with silver trifluoromethanesulfonate. The dimethylphosphido-bridged complex is found to work as a dual catalyst toward the redox isomerization of propargylic alcohols to alpha,beta-unsaturated ketones and sequential Friedel-Crafts reactions with heteroaromatic compounds.

As analogues of BINAP, optically active N,N,N',N'-tetraaryl-1,1'-binaphthyl-2,2'-diamines have been prepared by palladium-catalyzed coupling reactions of optically active 1,1'-binaphthyl-2,2'-diamine with an excess amount of aryl bromides. A novel diamine-bridged dirhodium T-arene complex has been produced and characterized by X-ray analysis.