/pdf/aryl-aryl-bond-formation-one-century-after-the-discovery-of-1jdyxlkwix.pdf

Aryl-aryl bond formation one century after the discovery of the Ullmann reaction.

https://www.erowid.org/archive/rhodium/pdf/suzuki.cross-coupling.review.1995-1998.pdf

Recent advances in the cross-coupling reactions of organoboron derivatives with organic electrophiles, 1995–1998

Because of the tremendous effort of a great number of researchers, the catalytic asymmetric dialkylzinc addition to aldehydes has become a mature method. Ligands of diverse structures have been obtained, and high enantioselectivity for all different types of aldehydes have been achieved. Among the representative excellent catalysts are compounds 1, 8, 120, 325, 352, and 360 discussed above. However, compared to the well-developed dialkylzinc addition, the catalytic asymmetric reactions of aryl-, vinyl-, and alkynylzinc reagents with aldehydes are still very much under developed. Although catalysts such as (S)-402 and 210 prepared by Pu and Bolm have shown good enantioselectivity for the reaction of diphenylzinc with certain aromatic and aliphatic aldehydes, the generality of these catalysts for other [formula: see text] arylzinc reagents have not been studied. The vinylzinc additions using ligands 1 and 412 reported by Oppolzer and Wipf were highly enantioselective for certain aromatic aldehydes but not as good for aliphatic aldehydes. Carreira discovered highly enantioselective alkynylzinc additions to aldehydes promoted by the chiral amino alcohol 415, but this process was not catalytic yet. Ishizaki achieved good enantioselectivity for the catalytic alkynylzinc addition to certain aldehydes by using compounds 160, but the enantioselectivity for simple linear aliphatic aldehydes was low. Another much less explored area is the organozinc addition to ketones. Yus and Fu showed very promising results by using ligands 381 and 406 for both dialkylzinc and diphenylzinc additions to ketones, but the scope of these reactions were still very limited. Therefore, more work is needed for the aryl-, vinyl-, and alkynylzinc additions and for the organozinc addition to ketones, although many good catalysts have been obtained for the dialkylzinc addition to aldehydes. Development of these reactions will allow the catalytic asymmetric synthesis of a great variety of functional chiral alcohols that are either the structural units or synthons of many important organic molecules as well as molecules of biological functions. Macromolecular chiral catalysts have become a very attractive research subject in recent years because these materials offer the advantages of simplified product isolation, easy recovery of the generally quite expensive chiral catalysts, and potential use for continuous production. Three types of macromolecules including flexible achiral polymers anchored with chiral catalysts, rigid and sterically regular main chain chiral polymers, and chiral dendrimers have been used for the asymmetric organozinc addition to aldehydes. Among these materials, the binaphthyl-based polymers such as (R)-451 developed by Pu have shown very high and general enantioselectivity. Study of the binaphthyl polymers in the asymmetric organozinc addition has demonstrated that it is possible to systematically modify the structure and function of the rigid and sterically regular polymer for the development of highly enantioselective polymer catalysts. The catalytic properties of highly enantioselective monomer catalysts can also be preserved in the rigid and sterically regular polymer provided the catalytically active species of the monomer catalyst is not its aggregate. The TADDOL-based polymers and dendrimers prepared by Seebach showed very high and stable enantioselectivity for the diethylzinc addition to benzaldehyde even after many cycles. These studies on macromolecular chiral catalysts demonstrate that these materials are potentially very useful for practical applications.

Catalytic Asymmetric Organozinc Additions to Carbonyl Compounds

Mixtures of palladium acetate and o-(di-tert-butylphosphino)biphenyl (4) catalyze the room-temperature Suzuki coupling of aryl bromides and aryl chlorides with 0.5−1.0 mol % Pd. Use of o-(dicyclohexylphosphino)biphenyl (2) allows Suzuki couplings to be carried out at low catalyst loadings (0.000001−0.02 mol % Pd). The process tolerates a broad range of functional groups and substrate combinations including the use of sterically hindered substrates. This is the most active catalyst system in terms of reaction temperature, turnover number, and steric tolerance which has been reported to date.

Highly Active Palladium Catalysts for Suzuki Coupling Reactions

2. Thiol Oxidation to Disulfides 3007 3. Epoxidation of Alkenes 3007 4. Oxidation of Bromide 3008 5. Oxidation of Mercaptoethanol by Dioxygen 3008 V. Particle−Dendrimer Assemblies 3008 1. Hydrogenation 3008 2. Heck Reaction 3010 3. Anodic Oxidation of Ethanol 3010 VI. Redox Catalysis 3010 1. Anodic Oxygen Reduction 3010 2. Cathodic Reduction of CO2 to CO 3010 3. Ferrocenes as Redox Mediators for Glucose Oxidation 3010

Dendritic Catalysts and Dendrimers in Catalysis

Novel, Blue‐Transparent Frequency Doublers Based on 1,8‐Di(hetero)arylnaphthalenes

Polarized π‐Electron Systems in a Chemically Generated Electric Field: Second‐Order Nonlinear Optical Properties of Ammonium/Borate Zwitterions

Hyper-Rayleigh scattering, HRS, is a powerful technique to extract the second-order polarizability, β, of organic chromophores. However, we show that the obtained β value, first, may differ depending on which of the three possible HRS data evaluation techniques is used and, second, may not agree with that determined by more conventional measurement techniques, such as electric field induced second harmonic generation, EFISH. The first problem is identified as being one essentially due to curve fitting when using the internal reference method, with the normalized internal reference method proposed as an alternative. The second problem has been identified as arising from a broad-band background signal which may contribute to the scattered intensity in the HRS measurement, underscoring the need to examine both the spectral purity of the scattered radiation and the dependence of the scattered intensity on fundamental intensity. This broad-band background has been examined in three molecules, where there was (...

Problems Associated with Hyper-Rayleigh Scattering as a Means To Determine the Second-Order Polarizability of Organic Chromophores

A hyper-Rayleigh scattering (HRS) system based on an optical parametric power oscillator is described. The first hyperpolarizability, β, of Crystal Violet dye was measured at 1450 and 1500 nm. The resonance-free β value, β(0), for this octupole was found to be comparable with that of the dipolar dye Disperse Red 1 but with the nonlinearity–transparency trade-off worse for the octupole. The discrepancy in β(0) with that reported previously is explained in terms of resonance and the adequacy of the octupolar three-state model. The possibility of dye aggregation by solvent-dependent HRS is investigated.

Stefan Stadler

Papers

Novel, Blue‐Transparent Frequency Doublers Based on 1,8‐Di(hetero)arylnaphthalenes

Polarized π‐Electron Systems in a Chemically Generated Electric Field: Second‐Order Nonlinear Optical Properties of Ammonium/Borate Zwitterions

Problems Associated with Hyper-Rayleigh Scattering as a Means To Determine the Second-Order Polarizability of Organic Chromophores

Long-wavelength first hyperpolarizability measurements by hyper-Rayleigh scattering.

First hyperpolarizability measurements via hyper-Rayleigh scattering at 1500 nm