Yoshiya Fukumoto

Nickel-catalyzed chelation-assisted transformations involving ortho C-H bond activation: regioselective oxidative cycloaddition of aromatic amides to alkynes.

Although the pioneering example of ortho metalation involving cleavage of C-H bonds was achieved using a nickel complex (Kleiman, J. P.; Dubeck, M. J. Am. Chem. Soc. 1963, 85, 1544), no examples of catalysis using nickel complexes have been reported. In this work, the Ni-catalyzed transformation of ortho C-H bonds utilizing chelation assistance, such as oxidative cycloaddition of aromatic amides with alkynes, has been achieved.

Highly regioselective carbonylation of unactivated C(sp3)-H bonds by ruthenium carbonyl.

The regioselective carbonylation of unactivated C(sp(3))-H bonds of aliphatic amides was achieved using Ru(3)(CO)(12) as a catalyst. The presence of a 2-pyridinylmethylamine moiety in the amide is crucial for a successful reaction. The reaction shows a preference for C-H bonds of methyl groups as opposed to methylene C-H bonds and tolerates a variety of functional groups. The stoichiometric reaction of an amide with Ru(3)(CO)(12) gave a dinuclear ruthenium complex in which the 2-pyridinylmethylamino moiety was coordinated to the ruthenium center in an N,N manner.

Ruthenium-catalyzed carbonylation at ortho C-H bonds in aromatic amides leading to phthalimides: C-H bond activation utilizing a bidentate system.

A new type of carbonylation of the ortho C-H bonds in aromatic amides 1, in which the pyridin-2-ylmethylamino moiety functions as a bidentate directing group, can be achieved. The presence of ethylene as a hydrogen acceptor and also of H(2)O, probably for the generation of an active catalytic species, is required. A wide variety of functional groups, including methoxy, amino, ester, ketone, cyano, chloro, and even bromo substituents, can be substituted for aromatic amides. The complex 9 was isolated by the stoichiometric reaction of 1b and Ru(3)(CO)(12), in which 1b binds to one Ru atom in the expected N,N fashion and the carbonyl oxygen binds to the other Ru atom as an O donor.

Ni(II)-Catalyzed Oxidative Coupling between C(sp2)–H in Benzamides and C(sp3)–H in Toluene Derivatives

Oxidative coupling between C(sp(2))-H bonds and C(sp(3))-H bonds is achieved by the Ni(II)-catalyzed reaction of benzamides containing an 8-aminoquinoline moiety as the directing group with toluene derivatives in the presence of heptafluoroisopropyl iodide as the oxidant. The method has a broad scope and shows high functional group compatibility. Toluene derivatives can be used as the coupling partner in an unreactive solvent.

Ruthenium‐Catalyzed Carbonylation of ortho CH Bonds in Arylacetamides: CH Bond Activation Utilizing a Bidentate‐Chelation System

Given that C H bonds are ubiquitous in organic chemistry, substrate functionalization by means of C H bond activation appears as a challenging, yet straightforward method in organic synthesis, which can eliminate the multiple steps and limitations associated with the preparation of pre-functionalized starting materials. A wide variety of transformations of C H bonds have been developed thus far and they have had a significant impact on organic synthesis, not only in academia, but also industrial processes. Regioselectivity is the most important issue that must be addressed in the transformation of C H bonds because organic molecules can have many different types of C H bonds. The use of a directing group can, for the most part, overcome the regio-control issues by allowing the catalyst to come into close proximity with the targeted C H bonds, which, in most cases, are ortho C H bonds. A wide variety of directing groups, such as ketones, esters, aldehydes, cyano, pyridine, and oxazoline derivatives, have been used in the chelation-assisted transformation of C H bonds. However, in most cases, structurally simple directing groups that can coordinate to a metal by a monodentate system were utilized. A well-designed bidentate directing group can potentially be used for the exploration of new catalytic reactions that have not yet been achieved using conventional directing groups. The first successful example of a bidentate, directing-group assisted transformation of C H bonds was reported by Daugulis et al. , who discovered the Pd-catalyzed arylation of C H bonds in amides, which consists of a 8-aminoquinoline moiety. Following such a pioneering finding, a number of reactions using 8-aminoquinoline and picolinamide-based bidentate directing groups have been developed, especially in the case of Pd-catalyzed reactions. This bidentate directing system is also applicable to other transition-metal-catalyzed transformations of C H bonds. In a previous study, we reported that the Ru-catalyzed C H bond carbonylation of aromatic amides with a 2-pyridinylmethylamine moiety as the bidentate directing group results in the formation of phthalimides, the formation of which involves the carbonylation of the ortho C H bonds. This new directing group was also applicable to the Ru-catalyzed carbonylation of unactivated C(sp) H bonds in alipthatic amides and the Ni-catalyzed oxidative annulation of aromatic amides with alkynes, leading to the formation of isoquinolones. Herein, we report on the Ru-catalyzed C H bond carbonylation of arylacetamides with a 2-pyridinylmethylamine moiety as the bidentate direction group. The reaction involves the regioselective activation of C(sp) H bonds at the ortho C H position. 9] The reaction of amide 1 a with CO was carried out under reaction conditions identical to those used in the reaction of aromatic amides (Ru3(CO)12 in toluene at 160 8C under 10 atm of CO for 24 h) to give the isoquinoline-1,3(2 H,4 H)-dione 2 a in 93 % yield. The absence of ethylene did not give 2 a, and, in the absence of H2O, the yield of 2 a was dramatically decreased to 26 %.

Ru3(CO)12-catalyzed reaction of yne–imines with carbon monoxide leading to bicyclic α,β-unsaturated lactams

The cyclocarbonylation of 1,6- and 1,7-yne–imines leading to bicyclic α,β-unsaturated lactams can be achieved in the presence of a catalytic amount of Ru3(CO)12. The reaction, a [2+2+1] cycloaddition, incorporates the acetylene π-bond, the imine π-bond, and the carbon atom of CO. The presence of substituents, such as alkyl, aryl, and silyl on the acetylenic terminal carbon is essential for yne–imines to undergo cyclocarbonylation to give bicyclic α,β-unsaturated lactams. An yne–imine having no substituents on the acetylenic terminal carbon does not give the corresponding lactam, but rather a dihydropyridine derivative without incorporating CO.

Rhenium-Catalyzed Regio- and Stereoselective Addition of Imines to Terminal Alkynes Leading to N-Alkylideneallylamines

The reaction of terminal alkynes with imines using ReBr(CO)(5) as a catalyst results in the production of N-alkylideneallylamines and not the conventional propargylamines. The substituent on the imine nitrogen is important, and a diphenylmethyl group gave the best result. The catalytic cycle of this regioselective C-C bond forming reaction appears to involve the formation of an alkynyl rhenium species and subsequent nucleophilic attack of the alkynyl β-carbon atom on the imine carbon to give a vinylidene rhenium species.

Switch in Stereoselectivity Caused by the Isocyanide Structure in the Rhodium-Catalyzed Silylimination of Alkynes

The reaction of terminal alkynes with hydrosilanes and tert-alkyl isocyanides in the presence of Rh(4)(CO)(12) gives (Z)-β-silyl-α,β-unsaturated imines in good yields. On the other hand, the use of aryl isocyanides in place of tert-alkyl isocyanides leads to the formation of E isomers.

Chelation-assisted carbonylation reactions catalyzed by Rh and Ru complexes

This account reviews chelation-assisted carbonylation reactions catalyzed by late transition metals. New carbonylation reactions are achieved with these catalysts in the presence of pyridin-2-ylmethanol and pyridin-2-ylmethylamine. The reactions involve activation of O-H and N-H bonds, coordination of the pyridine nitrogen to Rh being essential for the reaction to proceed. In addition, a new type of carbonylation of the ortho C-H bonds in aromatic amides in which the pyridin-2-ylmethylamino moiety functions as a bidentate directing group, is demonstrated. In this reaction, a dinuclear ruthenium complex was isolated from a stoichiometric reaction of amide and Ru3(CO)12, in which amide binds to one Ru atom in the expected N,N fashion and the carbonyl oxygen binds to the other Ru atom as an O-donor. These studies indicate that chelation methodology is useful for new types of carbonylation reaction, which cannot be achieved by non-chelation systems.

Ring-opening silylformylation of oxetanes catalyzed by [RhCl(CO)2]2-amine

Abstract With [RhCl(CO) 2 ] 2 -amine as catalyst, the reaction of oxetanes with a hydrosilane and carbon monoxide results in ring-opening silyformylation to give γ-siloxy aldehydes in 42–83% yields. Addition of amines is essential for the silyformylation to proceed, and 1-methylpyrazole is the most effective additive among the amines examined. The ring-opening of 2-alkyloxetanes occurs predominantly at the primary carbon atom with regioselectivity of 95%.