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Transition metal-catalyzed regioselective hydroboration of 1,3-dienes has received continuous interest in the field of organic synthesis. Herein, we describe the nickel-catalyzed Markovnikov 1,2-hy...

A study for the development of the nickel-catalyzed highly enantioselective propargylic amination of propargylic carbonates with aniline derivatives is described. The reaction of internal alkyne-su...

We demonstrated a ruthenium-catalyzed regioselective allylic amination of tertiary allylic esters with various amines using [Cp*Ru(CH3CN)3][PF6]/5,5′-dimethyl-2,2′-bipyridine (5,5′-diMe-2,2′-bpy) a...

The nickel-catalyzed highly enantioselective Friedel–Crafts propargylation of 3-substituted indoles with propargylic carbonates bearing an internal alkyne group was developed. A wide array of the propargylic carbonates as well as 3-substituted indoles can be applicable to the asymmetric nickel catalysis, providing the corresponding chiral C-3 propargylated indolenine derivatives bearing two vicinal chiral centers in up to 89% yield with up to >99% ee and 94:6 dr (24 examples).

We have accomplished the ruthenium-catalyzed benzylic substitution of benzyl esters with a stabilized carbon nucleophile. A [Cp*RuCl2]2/picolinic acid catalyst system promoted the reaction of 2-naphthylmethyl-2,3,4,5,6-pentafluorobenzoates with a series of stabilized carbon nucleophiles such as malonates, β-ketoesters, and diketones to give the corresponding benzylic alkylation products in moderate to high yields. We proposed a plausible reaction mechanism that could involve a (π-benzyl)ruthenium intermediate.

Nickel-catalyzed transformation of alkene-tethered oxime ethers to nitriles using a traceless directing group strategy has been developed. A series of alkene-tethered oxime ethers derived from benzaldehyde and cinnamyl aldehyde derivatives were converted into the corresponding benzonitriles and cinnamonitriles in 46-98% yields using the nickel catalyst system. Control experiments showed that the alkene group tethered to an oxygen atom on the oximes via one methylene unit plays a key role as a traceless directing group during the catalysis.

We investigated the palladium-catalyzed [2 + 2 + 1] cycloaddition of aryl- and trifluoromethyl-group-substituted internal alkynes and carbon monoxide, and revealed that the PdBr2 effectively catalyzed the intended reaction. The PdBr2-catalyzed reaction smoothly proceeded and provided aryl- and trifluoromethyl-group-containing cyclopentadienone derivatives in up to 92% yield.

We describe herein the synthetic method to benzoxazole derivatives via the copper-catalyzed hydroamination of alkynones with 2-aminophenols. The method produced a wide variety of functionalized benzoxazole derivatives in good yields. Preliminary mechanistic experiments revealed that the reaction would proceed through the copper-catalyzed hydroamination of alkynones and the sequential intramolecular cyclization of β-iminoketones/elimination of acetophenone promoted by the copper catalyst.

The synthesis of the trifluoromethyl group containing enol ethers by the palladium-catalyzed intermolecular reaction of 2,3,3-trifluoroallylic carbonates with oxygen nucleophiles was accomplished. The reaction proceeds through the intermolecular attack of oxygen nucleophiles on the C-2 carbon atom of the allylic unit, and the intramolecular fluorine atom shift from the C-2 position to the C-3 position. The reactions with several types of alcohols and phenols proceeded smoothly, and afforded the corresponding trifluoromethyl group containing enol ethers in good to high yields.

We accomplished the palladium-catalyzed double substitution of 2-haloallylic acetates with nitrogen nucleophiles. During the Pd2(dba)3/DPPE-catalyzed reaction of 2-fluoroallylic acetates with N-substituted-p-toluenesulfonamide, two equivalents of nitrogen nucleophiles were introduced to the allyl unit with a Z-selectivity through the carbon–fluorine bond cleavage. We further demonstrated the reaction of 2-chloroallylic acetates, and succeeded in obtaining the same doubly-substituted products in good yields with a high Z-selectivity.

We accomplished the synthesis of 2-substituted benzofuran derivatives by the palladium-catalyzed reaction of 2-haloallylic acetates with simple phenols in the presence of a base. The reaction proceeded through the intermolecular attack of the nucleophile on the central carbon atom of the π-allyl group, carbon-halogen bond cleavage, and sequential intramolecular cyclization.

We accomplished the synthesis of 2-substituted benzofuran derivatives by the palladium-catalyzed reaction of 3-substituted propargylic carbonates with phenols. The 2-substituted benzofuran derivatives were obtained through the intermolecular coupling of the 3-substituted propargylic carbonates with phenols, and sequential intramolecular cyclization reaction.

The nickel-catalyzed hydroarylation of 1,3-dienes with arylboronic acids using a secondary homoallyl carbonate as a surrogate for the 1,3-diene and hydride source has been developed. The synthetic strategy allowed an efficient access to a wide array of hydroarylation products in high yields with high functional group compatibility without the use of an external hydride source. Mechanistic experiments indicated that the alkene-directed oxidative addition and subsequent β-hydride elimination would be a critical process in this transformation.

We have developed a novel synthetic method accessing benzo[b][1,4]oxazepines that are one of the rare classes of benzoxazepine derivatives by reaction of 2-aminophenols with alkynones in 1,4-dioxane at 100 °C. A series of benzo[b][1,4]oxazepine derivatives can be prepared by using this synthetic protocol. Mechanistic experiments indicated that the hydroxy proton of the aminophenol could play a crucial role in the formation of an alkynylketimine intermediate that undergoes 7-endo-dig cyclization.

The nickel-catalyzed benzylic substitution of benzyl alcohol derivatives with a soft carbon nucleophile is extremely rare compared to that with a hard carbon nucleophile. We have achieved the nickel-catalyzed benzylic substitution of benzyl esters with malonates as a soft carbon nucleophile. Primary and secondary benzyl 2,3,4,5,6-pentafluorobenzoates as well as a wide variety of malonate derivatives were well tolerated in the nickel-catalyzed reaction, providing the corresponding alkylation products in 46–86% yields (34 examples). Additionally, we propose a possible reaction mechanism that would undergo via the η1- and η3-benzylnickel intermediates.

The transition metal-catalyzed stereospecific benzylic alkylation of optically active benzyl esters with active methylene compounds remains extremely rare. Herein, we describe the study for the ruthenium-catalyzed benzylic alkylation of chiral benzyl esters with malonates as a carbon nucleophile. A combination of [Cp*RuCl2]2 and picolinic acid found to be effective for the title reaction, providing the chiral benzylic alkylation products with retention of stereochemistry of the starting material. We proposed that the ruthenium catalysis would proceed via a double inversion mechanism.

A palladium-catalyzed three-component coupling reaction of 2-fluoroallylic acetates with phenols, and imides is disclosed. The reaction was effectively catalyzed by [Pd(C3H5)Cl]2/DPPF in the presence of Cs2CO3, and phenols and imides were introduced onto the allyl unit through the C–F bond activation. Furthermore, the reaction proceeds with both high regioselectivity and high Z-selectivity.

The palladium-catalyzed alkylation reaction of 2,3,3-trifluoroallylic carbonates with indoles afforded a trifluoromethyl group possessing 3-substituted indole derivatives. The reaction proceeded via attack of the C-3 carbon of the indoles onto the C-2 position of the allylic moiety and intramolecular construction of the trifluoromethyl group by the intramolecular fluorine atom shift from the C-2 position to the C-3 position of the allyl unit.

The ruthenium-catalyzed regioselective allylic amination of tertiary allylic acetates with several types of amines has been accomplished. The reaction was effectively catalyzed by Cp*RuCl2/5,5′-dimethyl-2,2′-bipyridine or its related ruthenium catalyst systems, and α,α-disubstituted allylic amines were formed as a single regioisomer in moderate to high yields.

We investigated the intermolecular coupling reaction of 2-fluoroallylic acetates with simple phenols by the [Pd(C 3 H 5 )Cl] 2 , DPPF, and KHMDS at 100 °C for 16 h, and succeeded in obtaining 2-substituted benzofuran derivatives in good to high yield through the C–F bond activation and intermolecular cyclization.

Direct N-alkylation of amines with carboxylic acids using a ruthenium catalyst with tris(pentafluorophenyl)phosphine as a ligand and methylphenylsilane as a reducing agent is described. Selective direct N-alkylation of amines was observed under these novel reaction conditions, and the corresponding mono-alkylated products were obtained in moderate to high yields with excellent selectivity. In addition, secondary amines were reacted with benzoic acid to afford the corresponding benzylated amines in moderate to high yields.

We demonstrated the intermolecular [2+2+2] cycloaddition of aryl- and trifluoromethyl-substituted internal alkyne and ethyl cyano­formate, and succeeded in constructing the pyridine derivatives using the CoI2/dcype/Zn catalyst system. The reaction proceeded with a high regioselectivity, and two trifluoromethyl-substituted ethyl picolinate derivatives were obtained as a single regioisomer.

Nazarov cyclization is an important and versatile method for the synthesis of five-membered carbocycles, and extensive studies have been conducted to optimize the reaction. Among recent studies, several trends are recognized. One is the combination of different reactions with Nazarov cyclization in a one-pot reaction system which enables the preparation of unique cyclization products. The second is the use of a transition-metal catalyst, though Lewis or Brønsted acids have generally been used for the reaction. The third is the realization of the asymmetric Nazarov cyclization. The fourth is the base-catalyzed Nazarov cyclization. Furthermore, several useful protocols for realizing Nazarov cyclization have also been developed. The recent progress on Nazarov cyclizations is summarized in Section 2. Section 3 is our chronicle in this field. We focused on the use of iron as the catalyst in Nazarov cyclizations and ionic liquids as solvents: Nazarov cyclization of thiophene derivatives using FeCl3 as the catalyst was accomplished and we succeeded in demonstrating the first example of an iron-catalyzed asymmetric Nazarov reaction. We next established Nazarov cyclization of pyrrole or indole derivatives using Fe(ClO4 )3 ·Al2 O3 as the catalyst with high trans selectivities in excellent yields. Since the cyclized product was reacted with a vinyl ketone in the presence of the same iron salt, the system allowed realization of the sequential type of Nazarov/Michael reaction of pyrrole derivatives. Furthermore, we demonstrated the recyclable use of the iron catalyst and obtained the desired Nazarov/Michael reaction products in good yields for five repetitions of the reactions without any addition of the catalyst using an ionic liquid, [bmim][NTf2 ], as the solvent. We expect that the iron-catalyzed Nazarov cyclization, in particular, in an ionic liquid solvent might become a useful method to synthesize functional molecules that include cycloalkene moieties.

The use of a malonate nucleophile in the transition metal-catalyzed hydroalkylation of 1,3-dienes remains immature. Herein, we report the nickel-catalyzed hydroalkylation of 1,3-dienes with malonates using a homoallyl carbonate as the 1,3-diene and hydride source. A broad range of homoally carbonates and malonate derivatives were well tolerated under a Ni/DPEphos catalyst system, providing the corresponding 1,2-hydroalkylation products in 40–94% yields with excellent regioselectivity (32 examples). We also suggested the possible reaction mechanism for the nickel-catalyzed hydroalkylation of in situ generated 1,3-dienes with malonates.

We have achieved the nickel-catalyzed asymmetric propargylic amination of propargylic carbonates bearing an internal alkyne group. A wide variety of propargylic carbonates and N-methylaniline derivatives were tolerated under the reaction conditions, providing the corresponding chiral propargylic amines in up to 97% yield with up to 97% ee.

We examined the palladium-catalyzed allylic alkylation of trifluoromethyl group-substituted racemic and acyclic unsymmetrical 1,3-disubstituted allylic benzoate with a malonate anion, and succeeded in obtaining an enantiomerically enriched product in high yields with high ee values through the dynamic kinetic asymmetric transformation (DYKAT). The best result was attained by the [Pd(C3H5)(cod)]BF4/(S)-tol-BINAP in the presence of BSA or DMAP as a base.

The palladium-catalyzed hydroalkylation of 2-fluoroallyl acetates with the malonate anion and hydride was developed. The reaction proceeded through the C–F bond activation and provided vinylmalonic acid ester derivatives by the regioselective substitutions with the carbon nucleophile and hydride.

We report the chemoselective amination of bromoiodobenzenes with diarylamines by palladium/Xantphos or a ligand-free copper catalyst. The reactions by these two types of catalysts proceeded with a high chemoselectivity and afforded monobrominated triarylamines in good yields. These products are useful intermediates for the synthesis of unsymmetrical bistriarylamines.

We demonstrate the iron-catalyzed intermolecular coupling of internal alkynes and thiosalicylic acid derivatives. The reaction was effectively catalyzed by the Fe(acac)2/1,10-phenanthroline catalyst in toluene/HFIP (hexafluoroisopropyl alcohol) as the reaction solvent and afforded several types of 1,3-oxathiine derivatives in moderate to high yields through the intermolecular hydrothiolation and sequential intramolecular cyclization.

The copper-catalyzed regioselective allylic cyanation of allylic compounds with trimethylsilyl cyanide (TMSCN) is described. Copper(I) iodide (CuI), copper(I) cyanide (CuCN) and copper(II) chloride (CuCl2) are shown to effectively catalyze the cyanation of various allylic substrates to afford the corresponding allylic cyanides in good yields and high regioselectivities. The reaction in the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO) reveals that the cyanation proceeds via a radical pathway.

The double substitution of 3-aryl-2-fluoroallyl acetates with phenols has been accomplished; the Pd(PPh 3 ) 4 catalyst system has effectively catalyzed the reaction to afford the doubly substituted product via carbon–fluorine bond activation.

The palladium-catalyzed regio- and enantioselective allylic amination of trifluoromethyl group substituted racemic and unsymmetrical 1,3-disubstituted allylic esters has been accomplished. The enantioselective formation of the α-type allylic amines was attained by the dynamic kinetic asymmetric transformation (DYKAT).

Direct N-alkylation of amines with alcohols in the presence of iron(III) phthalocyanine chloride as a catalyst in solvent-free conditions under microwave irradiation afforded the corresponding N-al...

The alkylation of (Z)-3-aryl-2-fluoroallyl acetate with the malonate anion by the [Pd(C3H5)(cod)]BF4/2,2'-bpy catalyst proceeds through the carbon-fluorine bond cleavage, and 2 equiv of the malonate nucleophile was introduced to the allyl substrate.

Iron-catalyzed [2 + 2 + 2] intermolecular cycloaddition of trifluoromethyl group substituted unsymmetrical internal alkynes afforded the corresponding trifluoromethyl group substituted benzene derivatives in high yield with excellent selectivity.

Palladium-catalyzed regioselective allylic amination of the α-trifluoromethyl group-substituted allyl acetate has been accomplished using Pd(OAc)2/DPPE and [Pd(π-allyl)(cod)]BF4/DPPF as catalysts. The selective formation of the γ-product was attained by the use of Pd(OAc)2/DPPE, while the α-product was obtained in the presence of [Pd(π-allyl)(cod)]BF4/DPPF. We also succeeded in synthesizing optically active allylic amines using Pd(OAc)2/DPPE and [Pd(π-allyl)(cod)]BF4/BINAP began from optically active trifluoromethyl-substituted allyl acetate. Furthermore, we established that kinetic resolution of two types of allylic amines was possible using enantioselective isomerization by the [Pd(π-allyl)(cod)]BF4/(S)-BINAP catalyst.

We demonstrated the ruthenium-catalyzed allylic amination of 2,3,3-trifluoroallylic carbonates with several types of amines. The reactions proceeded with several types of amines, and succeeded in obtaining polyfluorinated terminal alkenes possessing branched allylic amines as a single regioisomer.

The novel reaction conditions allow the direct mono-N-alkylation of primary aromatic amines.

We demonstrated the intermolecular [2+2+2] cycloaddition of aryl- and trifluoromethyl-substituted internal alkyne and ethyl cyano­formate, and succeeded in constructing the pyridine derivatives using the CoI2/dcype/Zn catalyst system. The reaction proceeded with a high regioselectivity, and two trifluoromethyl-substituted ethyl picolinate derivatives were obtained as a single regioisomer.

We examined the palladium-catalyzed allylic alkylation of trifluoromethyl group-substituted racemic and acyclic unsymmetrical 1,3-disubstituted allylic benzoate with a malonate anion, and succeeded in obtaining an enantiomerically enriched product in high yields with high ee values through the dynamic kinetic asymmetric transformation (DYKAT). The best result was attained by the [Pd(C3H5)(cod)]BF4/(S)-tol-BINAP in the presence of BSA or DMAP as a base.

The copper-catalyzed regioselective intermolecular hydroamination of the aryl and trifluoromethyl group or electron-withdrawing group substituted internal alkynes with amines has been accomplished. The reaction was effectively catalyzed by the ligand-free Cu(OTf)2 and afforded the intended amine derivatives in good yields after treatment of NaBH3CN.

Nazarov cyclization is an important and versatile method for the synthesis of five-membered carbocycles, and extensive studies have been conducted to optimize the reaction. Among recent studies, several trends are recognized. One is the combination of different reactions with Nazarov cyclization in a one-pot reaction system which enables the preparation of unique cyclization products. The second is the use of a transition-metal catalyst, though Lewis or Bronsted acids have generally been used for the reaction. The third is the realization of the asymmetric Nazarov cyclization. The fourth is the base-catalyzed Nazarov cyclization. Furthermore, several useful protocols for realizing Nazarov cyclization have also been developed. The recent progress on Nazarov cyclizations is summarized in Section 2. Section 3 is our chronicle in this field. We focused on the use of iron as the catalyst in Nazarov cyclizations and ionic liquids as solvents: Nazarov cyclization of thiophene derivatives using FeCl3 as the catalyst was accomplished and we succeeded in demonstrating the first example of an iron-catalyzed asymmetric Nazarov reaction. We next established Nazarov cyclization of pyrrole or indole derivatives using Fe(ClO4 )3 ·Al2 O3 as the catalyst with high trans selectivities in excellent yields. Since the cyclized product was reacted with a vinyl ketone in the presence of the same iron salt, the system allowed realization of the sequential type of Nazarov/Michael reaction of pyrrole derivatives. Furthermore, we demonstrated the recyclable use of the iron catalyst and obtained the desired Nazarov/Michael reaction products in good yields for five repetitions of the reactions without any addition of the catalyst using an ionic liquid, [bmim][NTf2 ], as the solvent. We expect that the iron-catalyzed Nazarov cyclization, in particular, in an ionic liquid solvent might become a useful method to synthesize functional molecules that include cycloalkene moieties.

N-alkyl amines are prepared with excellent selectivity by mono-alkylation of various primary aromatic amines with benzyl alcohols using microwave irradiation.

Sequential type one pot Nazarov/Michael reaction of pyrrole derivatives has been demonstrated using 5 mol% Fe(ClO4)3·Al2O as catalyst in an ionic liquid as solvent. We succeeded in obtaining 4,5-dihydrocyclopenta[b]pyrrol-6(1H)-one derivative in good yield for five repetitions of the reactions without any addition of the catalyst using an ionic liquid, [bmim][NTf2], as solvent system.

A study of the design of thiophene-substituted fulleropyrrolidine derivatives as the acceptor in photovoltaic cells has been carried out using poly(3-hexylthiophene) (P3HT) as the model donor polymer. It was found that five types of thiophene-substituted fulleropyrrolidine worked as a good acceptor partner with P3HT, and the highest power conversion efficiency ( PCE ) was obtained for 1-(2-(2-methoxyethoxy)ethyl)-2-(2-thiophen-2-yl)fulleropyrrolidine (2.99%); this is superior to that of the P3HT polymer including methyl [C60]-PCBM under the same experimental conditions.

A rational design of phosphonium ionic liquid for ionic liquid coated-lipase (IL1-PS)-catalyzed reaction has been investigated: very rapid transesterification of secondary alcohols was accomplished when IL1-PS was used as catalyst in tributyl((2-methoxyethoxy)methyl)phosphonium bis(trifluoromethanesulfonyl)amide ([P444MEM][NTf2]) or N-ethyl-N-((2-methoxyethoxy)methyl)-N-methylethanaminium bis(trifluoromethanesulfonyl)amide ([N221MEM][NTf2]) as solvent with excellent enantioselectivity. It was also revealed that ammonium ionic liquid influenced the lipase reactivity more strongly than phosphonium ionic liquids. Increased Kcat value was suggested to be the most important factor at work in IL1-PS in these ionic liquid solvents. The Kcat value of (S)-1-phenyethanol in [N444MEM][NTf2] was similar to that of i-Pr2O, and 1.6-fold acceleration was achieved for (R)-1-phenylethanol. On the other hand, the Km value for (R)-isomer in [N444MEM][NTf2] was slightly larger than the reaction in i-Pr2O, while it was signif...

The palladium-catalyzed regioselective allylic amination of the α-trifluoromethyl group-substituted allyl acetate has been accomplished using Pd(OAc)2/DPPE and [Pd(π-allyl)(cod)]BF4/DPPF as catalysts. The selective formation of the γ-product was attained in the presence of Pd(OAc)2/DPPE, while the α-product was obtained using [Pd(π-allyl)(cod)]BF4/DPPF. We also succeeded in the regioselective synthesis of the enantiomerically enriched aminated product from chiral allyl acetate using Pd(OAc)2/DPPE and [Pd(π-allyl)(cod)]BF4/(S)-BINAP. Furthermore, we found that kinetic resolution had occurred during the isomerization step from the γ-type product to the α-type product by the [Pd(π-allyl)(cod)]BF4/(S)-BINAP catalyst.