A New Synthetic Approach to Phenol Derivatives: Use of Ring-Closing Olefin Metathesis

Phenol derivatives, which are one of the most important classes of aromatic compounds in organic chemistry, were synthesized by ruthenium-catalyzed ring-closing olefin metathesis (RCM) of 1,4,7-trien-3-ones with versatile substitution patterns. The RCM reaction for producing phenol derivatives was also successful with 1,5,7-trien-3-one as another precursor. Most of the phenols prepared here could not be obtained easily by conventional methods

A New c<i>ine</i>-Substitution of Alkenyl Sulfones with Aryltitanium Reagents Catalyzed by Rhodium: Mechanistic Studies and Catalytic Asymmetric Synthesis of Allylarenes

The reaction of alkenyl sulfones with aryltitanium triisopropoxide (ArTi(OPr-i )3) in the presence of 3 mol % of [Rh(OH)((S)-binap)]2 in THF at 40 °C gave high yield of cine-substitution products. The catalytic cycle was established by deuterium-labeling studies, and it was applied to catalytic asymmetric synthesis of allylarenes which proceeds with over 99% enantioselectivity

Chiral Bicyclic NHC/Rh Complexes and Their Application to Catalytic Asymmetric Ring-Opening Reaction of Oxabenzonorbornadienes with Amines

A rhodium complex bearing a chiral bicyclic NHC ligand, [RhCl­(3az)­(cod)] 4az, was synthesized and fully characterized by X-ray diffraction analysis, high-resolution mass spectrometry, and multinuclear NMR spectroscopy. The electronic and steric properties of NHC ligand 3az were evaluated by IR measurement and X-ray diffraction analysis of dicarbonyl complex [RhCl­(3az)­(CO)2] 5az, which was prepared by replacing the COD ligand of 4az with CO. The potential of novel complex 4az as a chiral catalyst was investigated in the Rh-catalyzed asymmetric ring-opening reaction of oxabenzo­norborna­dienes with amines, and the corresponding products were afforded in good yields with good enantioselectivities (up to 81% ee)

Catalytic Asymmetric Three-Component Mannich-Type Reaction of Alkenyl Trichloroacetates

A catalytic enantioselective three-component Mannich-type reaction of alkenyl trichloroacetates, ethyl glyoxalate, and aniline derivatives was achieved using an (S)-BINOL-derived chiral tin dibromide possessing a 4-trifluoromethylphenyl group at the 3- and 3′-positions as the chiral precatalyst in the presence of sodium ethoxide, sodium iodide, and ethanol. Optically active β-amino ketones with up to 98% ee were syn-selectively obtained in high yields even from imines possessing a polar amino group under the influence of the in situ generated chiral tin bromide ethoxide

Enantioselective Hydrogenation of Acyclic Aromatic <i>N</i>-Aryl Imines Catalyzed by an Iridium Complex of (<i>S,S</i>)-1,2-Bis(<i>tert</i>-butylmethylphosphino)ethane

An iridium(I) complex of (S,S)-1,2-bis(tert-butylmethylphosphino)ethane with tetrakis(3,5-bis(trifluoromethyl)phenyl)borate as the counterion catalyzes the hydrogenation of acyclic aromatic N-aryl imines under 1 atm of hydrogen pressure at room temperature to give the corresponding optically active secondary amines with up to 99% ee

Synthesis of Carbocyclic Aromatic Compounds Using Ruthenium-Catalyzed Ring-Closing Enyne Metathesis

General synthetic methods of substituted carbocyclic aromatic compounds are reported. Ring-closing enyne metathesis (RCEM)/dehydration of 1,5-octadien-7-yn-4-ols 6 and RCEM/tautomerization of 1,5-octadien-7-yn-4-ones 7 furnished a wide variety of substituted styrenes 4 and 4-vinylphenols 8, respectively. Acyclic precursors 6 and 7 were readily prepared from β-halo-α,β-unsaturated aldehydes 9 or 3-halo-2-propene-1-ols 13 by utilizing combinations of the Sonogashira coupling, allylation, and the Dess−Martin oxidation. The RCEM/dehydration for the synthesis of 1,3,5-tris(1-phenylethenyl)benzene derivative 4r and the RCEM/RCM/dehydration for the synthesis of 1,1′-binaphthyl derivative 19a are also presented as applications of this method

Complexation Stabilized Conformational Regulation of Ferrocene Bearing Podand Dipeptide Chains (-l-Ala-l-Pro-NHPy)

The structural characterization of the palladium complex of the ferrocene 1 bearing podand dipeptide chains (-l-Ala-l-Pro-NHPy) was demonstrated. The ferrocene 1 forms the 1:1 trans complex 2 with PdCl2(MeCN)2 to stabilize the intramolecular conformational regulation in both solution and solid states. The crystal structure of 2 revealed a pseudohelical conformation through palladium binding and chirality organization via sterically constrained moieties (Pro) and intramolecular hydrogen bondings between CO (Ala) and NH (another Ala) of each podand dipeptide chain (N(1)···O(2*), 2.88 Å; N(1*)···O(2), 2.97 Å), giving a 10-membered hydrogen-bonded ring. Such an ordered conformation was supported by the induced circular dichroism. Another noteworthy feature of the ferrocene 1 is its strong tendency to self-assemble through participation of all available hydrogen-bonding donors in the solid state

2,2‘-Bis(diphenylphosphino)-1,1‘-biphenyl: New Entry of Bidentate Triarylphosphine Ligand to Transition Metal Catalysts

The bidentate triaryl phosphine 2,2‘-bis(diphenylphosphino)-1,1‘-biphenyl (dpbp) was examined as a supporting ligand in several transition metal catalysts. The dpbp complexes showed superior catalytic activity to the corresponding complexes of other bisphosphines in Pd-catalyzed Grignard cross-coupling and Rh-catalyzed Michael addition of boronic acid. In the Pd-catalyzed Grignard cross-coupling of sec-BuMgCl, the Pd-dpbp catalyst showed nearly perfect secondary selectivity in the product. This selectivity is much higher than that of Pd catalysts with other standard bisphosphines and is comparable only with that of the corresponding Pd-dppf catalyst. Dpbp was also applied to Rh-catalyzed conjugate addition of boronic acids to enones, and the Rh(acac)(C2H4)2/dpbp catalyst exhibited excellent catalytic activity, which is far better than the corresponding catalyst with dppb. The structure of the dpbp complex PdCl2(dpbp) was studied by X-ray single-crystal structure determination, which clarified the bite angle of dpbp in the complex being 92.24°

Chirality-Organized Ferrocene Receptor Bearing Podand Dipeptide Chains (−l-Ala-l-Pro-NHPyMe) for the Selective Recognition of Dicarboxylic Acids

The ferrocene receptor bearing the podand dipeptide chains (−l-Ala-l-Pro-NHPyMe) was found to provide a chirality-organized binding site through two intramolecular interchain hydrogen bonds between CO (Ala) and NH (another Ala) of each podand dipeptide chain. The size-selective and chiral recognition of dicarboxylic acids was achieved by multipoint hydrogen bonds of the binding site