Economical and Readily Accessible Preparation of ,-Disubstituted Arylboronates through Palladium-Catalyzed Borylation of Haloarenes.

Miyaura borylation, that is, palladium-catalyzed cross-coupling between bromoarenes and diboron, offers a versatile method for preparing arylboronates; however, a costly and inaccessible catalyst has been required for synthesizing highly congested arylboronates with the method. Here the Pd(OAc)-tri(4-methoxyphenyl)phosphine catalyst was found to work as an efficient catalyst for the sterically demanding borylation. A broad range of ,-disubstituted bromoarenes were converted into the corresponding arylboronates in high yields by using the palladium catalyst with CsCO in EtOAc at 80 °C.

Ruthenium-Catalyzed Chemo- and Enantioselective Hydrogenation of Isoquinoline Carbocycles.

A chemoselective hydrogenation of isoquinoline carbocycles was achieved by using the catalyst prepared from Ru(methallyl)(cod) and trans-chelate chiral ligand PhTRAP. The unique chemoselectivity achieved in this hydrogenation could be ascribed to the trans-chelation of the chiral ligand. The procedure for preparing the catalyst strongly affects the reproducibility of the carbocycle hydrogenation.

Asymmetric Hydrogenation of Azaindoles: Chemo- and Enantioselective Reduction of Fused Aromatic Ring Systems Consisting of Two Heteroarenes.

High enantioselectivity was achieved for the hydrogenation of azaindoles by using the chiral catalyst, which was prepared from [Ru(η(3) -methallyl)2 (cod)] and a trans-chelating bis(phosphine) ligand (PhTRAP). The dearomative reaction exclusively occurred on the five-membered ring, thus giving the corresponding azaindolines with up to 97:3 enantiomer ratio.

Asymmetric Hydrogenation of Isoxazolium Triflates with a Chiral Iridium Catalyst.

The iridium catalyst [IrCl(cod)]2 -phosphine-I2 (cod=1,5-cyclooctadiene) selectively reduced isoxazolium triflates to isoxazolines or isoxazolidines in the presence of H2 . The iridium-catalyzed hydrogenation proceeded in high-to-good enantioselectivity when an optically active phosphine-oxazoline ligand was used. The 3-substituted 5-arylisoxazolium salts were transformed into 4-isoxazolines with up to 95:5 enantiomeric ratio (e.

Catalytic asymmetric hydrogenation of quinoline carbocycles: unusual chemoselectivity in the hydrogenation of quinolines.

The reduction of quinolines selectively took place on their carbocyclic rings to give 5,6,7,8-tetrahydroquinolines, when the hydrogenation was conducted in the presence of a Ru(η(3)-methallyl)2(cod)-PhTRAP catalyst. The chiral ruthenium catalyst converted 8-substituted quinolines into chiral 5,6,7,8-tetrahydroquinolines with up to 91 : 9 er.

Catalytic asymmetric hydrogenation of pyrimidines.

The asymmetric hydrogenation of pyrimidines proceeded with high enantioselectivity (up to 99% ee) using an iridium catalyst composed of [IrCl(cod)]2, a ferrocene-containing chiral diphosphine ligand (Josiphos), iodine, and Yb(OTf)3 (cod = 1,5-cyclooctadiene). The chiral catalyst converted various 4-substituted pyrimidines into chiral 1,4,5,6-tetrahydropyrimidines in high yield. The lanthanide triflate is crucial for achieving the high enantioselectivity as well as for activating the heteroarene substrate.

Catalytic asymmetric hydrogenation of 3-substituted benzisoxazoles.

A variety of 3-substituted benzisoxazoles were reduced with hydrogen using the chiral ruthenium catalyst, {RuCl(p-cymene)[(R,R)-(S,S)-PhTRAP]}Cl. The ruthenium-catalyzed hydrogenation proceeded in high yield in the presence of an acylating agent, affording α-substituted o-hydroxybenzylamines with up to 57% ee. In the catalytic transformation, the N-O bond of the benzisoxazole substrate is reductively cleaved by the ruthenium complex under the hydrogenation conditions.

Intramolecular SN'-type aromatic substitution of benzylic carbonates at their para-position.

The benzylic carbonates, which connect with an active methine through an o-phenylene tether at their meta-position, are cyclized by Pd(η(3)-C(3)H(5))Cp-S-Phos catalyst, yielding 3-methyl-9,10-dihydrophenanthrenes. In the catalytic cyclization, the internal nucleophile attacks not the ortho-carbon but the para-carbon of the benzylic ester. The [3 + 2] cycloaddition of m-(silylmethyl)benzyl carbonates with alkylidene malonates was developed from the palladium-catalyzed intramolecular S(N)'-type aromatic substitution.

Catalytic asymmetric hydrogenation of N-Boc-imidazoles and oxazoles.

Substituted imidazoles and oxazoles were respectively hydrogenated into the corresponding chiral imidazolines and oxazolines (up to 99% ee). The highly enantioselective hydrogenation was achieved by using the chiral ruthenium catalyst, which is generated from Ru(η(3)-methallyl)(2)(cod) and a trans-chelating chiral bisphosphine ligand, PhTRAP. This is the first successful catalytic asymmetric reduction of 5-membered aromatic rings containing two or more heteroatoms.

Palladium-catalyzed [4 + 2] cycloaddition of o-(silylmethyl)benzyl esters with ketones: an equivalent to oxo-Diels-Alder reaction of o-xylylenes.

o-(Silylmethyl)benzyl carbonates reacted with various electron-deficient ketones in the presence of a palladium catalyst, affording the [4 + 2] cycloaddition products, isochromanes, in high yields. The palladium-catalyzed cycloaddition is equivalent to the oxo-Diels-Alder reaction of o-xylylene with ketones. The regioselectivities were extraordinarily affected by the structures of the o-xylylene precursors and ketones.

Fluorescence and chemiluminescence properties of indolylmaleimides: experimental and theoretical studies.

Various indolylmaleimides (IMs) were synthesized, and their fluorescence (FL) and chemiluminescence (CL) were measured. The substitution at the 2-position of the indole ring and the 3- or 4-position of the maleimide moiety caused an obvious change in the FL and CL of the IMs. An almost on-off switching of the FL of the IMs was observed.

[4+2] cycloaddition of o-xylylenes with imines using palladium catalyst.

The cycloaddition of o-(silylmethyl)benzylic carbonates with imines proceeded in the presence of the Pd(eta(3)-C(3)H(5))Cp-DPPPent catalyst, affording the tetrahydroisoquinolines in good to high yields. The reaction rate was remarkably increased by a fluoride additive. In the catalytic cycloaddition, the palladium(0) reacted with the benzylic substrate to form 2-palladaindane, which works as an o-xylylene equivalent.

Nickel-catalyzed formation of a carbon-nitrogen bond at the beta position of saturated ketones.

Gone fishing: When propiophenone and related ethyl ketones are treated with morpholine in the presence of K(3)PO(4), chlorobenzene, and [Ni(cod)(2)]/PMe(3) catalyst, a carbon-nitrogen bond is formed selectively at the beta position (see scheme; cod = cycloocta-1,5-diene). Secondary amines were employed as substrates to give the corresponding beta-enaminones.

Benzyl protection of phenols under neutral conditions: palladium-catalyzed benzylations of phenols.

Benzyl protection of phenols under neutral conditions was achieved by using a Pd(eta3-C3H5)Cp-DPEphos catalyst. The palladium catalyst efficiently converted aryl benzyl carbonates into benzyl-protected phenols through the decarboxylative etherification. Alternatively, the nucleophilic substitution of benzyl methyl carbonates with phenols proceeded in the presence of the catalyst, yielding aryl benzyl ethers.

Suzuki-Miyaura coupling of diarylmethyl carbonates with arylboronic acids: a new access to triarylmethanes.

Suzuki-Miyaura coupling of diarylmethyl carbonates with arylboronic acids proceeded in the presence of [Pd(eta3-C3H5)Cl]2-DPPPent (1,5-bis(diphenylphosphino)pentane) catalyst, yielding a variety of triarylmethanes.

Catalytic asymmetric hydrogenation of 2,3,5-trisubstituted pyrroles.

Catalytic asymmetric hydrogenation of N-Boc-protected pyrroles proceeded with high enantioselectivity by using a ruthenium catalyst modified with a trans-chelating chiral bisphosphine PhTRAP. The ruthenium catalyst prepared from Ru(eta3-methallyl)2(cod) and (S,S)-(R,R)-PhTRAP in the presence of triethylamine was the most enantioselective for the asymmetric hydrogenation of methyl pyrrole-2-carboxylate, giving the desired (S)-proline derivative with 79% ee in 92% yield. Moreover, 2,3,5-trisubstituted pyrroles bearing a large substituent at the 5-position were hydrogenated with 93-99.

Bisindolylmaleimides with large Stokes shift and long-lasting chemiluminescence properties.

Various bisindolylmaleimides have fluorescence emission maxima wavelengths longer than 500 nm, large Stokes shifts longer than 200 nm, different fluorescence emission wavelengths at an excitation wavelength of 365 nm, and a long-lasting chemiluminescence. The expansion of the pi-conjugation, the pi-bond electronic structure, and oxidation of the C=C bond at the 2,3-position of the maleimide moiety are crucial for producing these fluorescence and chemiluminescence properties.

Ruthenium-catalyzed asymmetric hydrogenation of N-boc-indoles.

Highly enantioselective hydrogenation of various N-Boc-indoles proceeded successfully in the presence of the ruthenium complex generated from an appropriate ruthenium precursor and a trans-chelate chiral bisphosphine PhTRAP. Various 2- or 3-substituted indoles were converted into chiral indolines with high enantiomeric excesses (up to 95% ee). The PhTRAP-ruthenium catalyst was able to promote the hydrogenation of 2,3-dimethylindoles, giving cis-2,3-dimethylindolines with 72% ee.

Cross-coupling of benzylic acetates with arylboronic acids: one-pot transformation of benzylic alcohols to diarylmethanes.

Benzylic acetates reacted with arylboronic acids in the presence of a DPEphos-[Pd(eta3-C3H5)Cl]2 catalyst when tert-amyl alcohol was used as a solvent, and the catalytic cross-couplings produced diarylmethanes in high yields (up to 94% isolated yield).

Asymmetric Carroll rearrangement of allyl alpha-acetamido-beta-ketocarboxylates catalysed by a chiral palladium complex.

Asymmetric decarboxylative rearrangement (Carroll rearrangement) of allyl alpha-acetamido-beta-ketocarboxylates was catalysed by a palladium complex modified with a chiral phosphine ligand, giving optically active gamma,delta-unsaturated alpha-aminoketones with up to 90% ee.

Transformation of carbonates into sulfones at the benzylic position via palladium-catalyzed benzylic substitution.

[reaction: see text] The nucleophilic substitution of benzylic carbonates with sodium arenesulfinates was catalyzed by the palladium complex generated in situ from [Pd(eta(3)-C(3)H(5))Cl](2) and DPEphos [bis(2-diphenylphosphinophenyl)ether]. The catalytic reaction proceeded in DMSO at 80 degrees C and gave a variety of benzylic sulfones in high yields.