Spin trapping: ESR parameters of spin adducts.

Palladium-catalyzed carbonylation reactions of aromatic halides in the presence of various nucleophiles have undergone rapid development since the pioneering work of Heck and co-workers in 1974, such that nowadays a plethora of palladium catalysts are available for different carbonylative transformations. The carboxylic acid derivatives, aldehydes, and ketones prepared in this way are important intermediates in the manufacture of dyes, pharmaceuticals, agrochemicals, and other industrial products. In this Review, the recent academic developments in this area and the first industrial processes are summarized.

Palladium-catalyzed carbonylation reactions of aryl halides and related compounds.

Nickel-Catalyzed Cross-Couplings Involving Carbon-Oxygen Bonds Brad M. Rosen, Kyle W. Quasdorf, Daniella A. Wilson, Na Zhang, Ana-Maria Resmerita, Neil K. Garg,* and Virgil Percec* Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United States Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States

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Nickel-Catalyzed Cross-Couplings Involving Carbon-Oxygen Bonds

A rotationally hindered and thus stereogenic biaryl axis is the structurally and stereochemically decisive element of a steadily growing number of natural products, chiral auxiliaries, and catalysts. Thus, it is not surprising that significant advances have been made in the asymmetric synthesis of axially chiral biaryl compounds over the past decade. In addition to the classic approach (direct stereoselective aryl-aryl coupling), innovative concepts have been developed in which the asymmetric information is introduced into a preformed, but achiral-that is, symmetric or configurationally labile-biaryl compound, or in which an aryl--C single bond is stereoselectively transformed into an axis. This Review classifies these strategies according to their underlying concepts and critically evaluates their scope and limitations with reference to selected model reactions and applications. Furthermore, the preconditions required for the existence of axial chirality in biaryl compounds are discussed.

Atroposelective Synthesis of Axially Chiral Biaryl Compounds

Catalytic cross-coupling reactions in biaryl synthesis

Catalytic asymmetric synthesis of axially chiral biaryls by palladium-catalyzed enantioposition-selective cross-coupling.

Preparation of optically active binaphthylmonophosphines (MOP's) containing various functional groups

Aqueous solutions of L-alanylglycine and L-alanyl-L-alanine were ..gamma.. irradiated in the presence of a spin trap, 2-methyl-2-nitrosopropane. Stable sspin adducts produced in the ..gamma..-irradiated solutions were analyzed by high-performance liquid chromatography and ESR spectroscopy. The following spin adducts were found and identified: t-BuN(O)CH-(CH/sub 3/)CONHCH/sub 2/COO/sup -/ (I), NH/sub 3//sup +/-*CH(CH/sub 3/)CONH-*CH(COO/sup -/)N(0)-t-Bu (II), and t-BuN(0)CH/sub 2/CH(NH/sub 3//sup +/)-CONHCH/sub 2/COO/sup -/(III) from L-alanylglycine; t-BuN(0)-*CH(CH/sub 3/)CONH-*CH(CH/sub 3/)COO/sup -/ (IV), NH/sub 3//sup +/-*CH(CH/sub 3/)-CONH-*C(CH/sub 3/)(COO/sup -/)N(0)-t-Bu (V), NH/sub 3//sup +/CH(CH/sub 3/)CONHCH(COO/sup -/)CH/sub 2/N(O)-t-Bu (VI), and t-Bu-N(0)-CH/sub 2/CH(NH/sub 3//sup +/)CONHCH(CH/sub 3/)COO/sup -/ (VII) from L-alanyl-L-alanine. Each of sspin adducts II, IV, and V was found as a pair of diastereomeric radicals, which revealed mutually different hyperfine splitting constants. The two diastereomeric pairs of spin adducts II and V were individually separated. It was demonstrated that ESR spectra of spin adducts II, III, and VI changed remarkably with pH through the acid-dissociation equilibria of the carboxyl or amino groups. The pK/sub a/ values for the dissociation have been determined to be 1.8 and 1.6 for the carboxyl groups of the pair of diastereomeric pin adducts II. The pK/sub COOH/ values are lower than that of alanylglycine because of the electron-withdrawing character of the nitroxyl group.more » 12 figures, 2 tables.« less

Studies on spin-trapped radicals in. gamma. -irradiated aqueous solutions of L-alanylglycine and L-alanyl-L-alanine by high-performance liquid chromatography and ESR spectroscopy

Radiolyse γ de la cis-chloro-4-L proline et de la cis-hydroxy-4 en presence d'intercepteurs de spin (methyl-2 nitroso-2 propane. Etude par chromatographie haute performance et spectres RPE des nitroxyles t-Bu (NO) d'addition de spin. Coexistence de paires de composes d'addition diastereoisomeriques. Mecanismes

Studies on spin-trapped radicals in .gamma.-irradiated aqueous solutions of cis-4-chloro-L-proline and cis-4-hydroxy-L-proline by high-performance liquid chromatography and ESR spectroscopy

Optically active 2′-diphenylphosphino-1,1′-binaphthyls (MOP's) having various functional groups, cyano, aminomethyl, methoxycarbonyl, carboxy, and hydroxymethyl, at the C2-position were prepared. A cyano group was introduced on the MOP skeleton by nickel-catalyzed cyanation of 2-diphenylphosphinyl-2′-trifluoromethanesulfonyloxy 1,1′-binaphthyl which is readily prepared from optically active binaphthol. Preparation of the MOP derivatives bearing carboxylic groups were achieved by palladium-catalyzed monocarbonylation of binaphthyl 2,2′-bis(triflate) followed by phosphinylation of the remaining triflate group.

Nobuhiro Suzuki

Papers

Catalytic asymmetric synthesis of axially chiral biaryls by palladium-catalyzed enantioposition-selective cross-coupling.

Preparation of optically active binaphthylmonophosphines (MOP's) containing various functional groups

Studies on spin-trapped radicals in. gamma. -irradiated aqueous solutions of L-alanylglycine and L-alanyl-L-alanine by high-performance liquid chromatography and ESR spectroscopy

Studies on spin-trapped radicals in .gamma.-irradiated aqueous solutions of cis-4-chloro-L-proline and cis-4-hydroxy-L-proline by high-performance liquid chromatography and ESR spectroscopy

Preparation of Optically Active Binaphthylmonophosphines (MOP′s) Containing Various Functional Groups.