A new catalytic method for the synthesis of selectively substituted biphenyls containing an oxoalkyl chain (original) (raw)
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Advanced Synthesis & Catalysis, 2007
A 4-hydroxyacetophenone oxime-derived palladacycle catalyzes the Mizoroki-Heck reaction of allyl alcohols with aryl iodides, bromides, and chlorides in aqueous and organic solvents. The reaction takes place in the presence of dicyclohexylmethylamine or cesium carbonate as bases, the addition of tetrabutylammonium bromide (TBAB) as additive for aryl bromides and chlorides being necessary. Under these reaction conditions, b-arylated aldehydes and ketones are mainly obtained using a rather low loading of palladium (0.1-1 mol %). Similar catalytic activity is shown by a Kaiser oxime resin-derived palladacycle, which allows one to perform recycling and reusing experiments with low Pd leaching. The high regio-and chemoselectivity observed supported that these palladacycles, working as a source of Pd(0) species, operates mainly through a neutral mechanism. This methodology has been applied to the synthesis of important b-arylated carbonyl compounds, such as 4-phenylbutan-2-one, 4-(4-hydroxyphenyl)butan-2-one, dihydrochalcones, the anti-inflamatory nabumetone, and the fragance blilial . g-Arylation is observed in the reactions of allyl alcohol and but-3-en-2-ol with 2-iodoaniline giving mainly the corresponding quinolines. The same tendency is observed in the case of 1,1-dimethylallyl alcohol affording either g-arylated alcohols or (E)-1-arylisoprenes.
New catalytic methods for the synthesis of selectively substituted aromatics through palladacycles
Pure and Applied Chemistry, 2005
Joint palladium and norbornene catalysis for selective aromatic functionalization via palladacycles is reported. Both alkylation and arylation of aromatics are considered after a brief outlook on the mechanism. These are multistep reactions that proceed in ordered sequences and are chemio-, regio-, and stereoselective. The study of the single steps with isolation of the organometallic species involved has allowed us to detect subtle steric and electronic effects which have been exploited to achieve catalytic reactions. Recent developments of aromatic alkylation and arylation are reported, in particular, condensed heterocyclic ring formation involving dialkylated arylpalladium complexes or both symmetrically and unsymmetrically substituted biphenylylpalladium complexes.
Palladium-Catalyzed Allylic Acyloxylation of Terminal Alkenes in the Presence of a Base
The Journal of Organic Chemistry, 2010
The efficiency and the selectivity of the Pd-catalyzed oxidation, in carboxylic acids, of terminal alkenes are strongly improved in the presence of a base. The methodology is particularly well adapted for the oxidation of homoallylic alcohols, for which the resulting acyloxylated products are obtained selectively as E-isomers in fair to good yields. Palladium(II)-catalyzed allylic oxidation of internal or cyclic olefins in acetic acid is an efficient process for the synthesis of allylic acetates. 1 On the other hand, terminal olefins generally yield mixtures of allylic acetates, vinyl acetates, and ketones. 2 Recently, two important progresses have been achieved toward more selective transformations. White et al. demonstrated that the association of Pd(OAc) 2 , benzoquinone (BQ), and DMSO or a bis(sulfoxide) ligand promoted the regio-and stereoselective allylic acetoxylation of terminal alkenes. In addition, either linear or branched products were selectively obtained depending on the reaction conditions. 3 This methodology has been applied in the total synthesis of 6-deoxyerythronolide B, through a C-H oxidative macrolactonization, increasing the overall efficiency of the synthesis and providing stereochemical control at a key lactone position. 4 Kaneda and co-workers described a regioselective process leading to linear allylic acetates using N,N-dimethylacetamide (DMA) as solvent and molecular oxygen as the sole oxidant, high pressures of O 2 (6 atm) being required, however. 5 Bipyrimidines as ligands were also found to improve the allylic acetoxylation of olefins. The proposed mechanism of such transformations generally involves π-allyl-Pd(II) intermediates. 3f,6,7 Surprisingly, the influence of additives, such as acetate salts, has not received so much attention for the oxidation of terminal olefins. 8 Such compounds could act as bases to facilitate the formation of π-allyl complexes, 9 and as nucleophiles on such complexes. Herein, we disclose our results on the use of bases for the Pd-catalyzed oxidation of terminal alkenes.
Synthesis of Biindolyls via Palladium-Catalyzed Reactions
The Journal of Organic Chemistry, 2008
An unprecedented synthesis of a range of high value homoand heterobiindolyls is presented. The one-pot Miyaura borylation and subsequent Suzuki-Miyaura coupling sequence allows for the construction of the highly sterically congested C-C bond between two bromoindoles in modest to good overall yields.
Tetrahedron, 2012
A general and efficient procedure for the stereoselective synthesis of (E)-(1-propenyl)phenyl esters from readily accessible allylphenols has been developed. The process involves a two-step sequence consisting of the initial acylation of the allylphenols with an acid chloride, followed by catalytic C]C bond isomerization in the resulting allylphenyl esters. The latter step was performed in methanol at 80 C using catalytic amounts (0.5 mol %) of the commercially available bis(allyl)-ruthenium(IV) dimer [{RuCl(m-Cl)(h 3 :h 3 -C 10 H 16 )} 2 ] (C 10 H 16 ¼2,7-dimethylocta-2,6-diene-1,8-diyl). Reactions proceeded in high yields (68e93%) and short times (4e9 h) with complete E-selectivity.
Arabian Journal of Chemistry, 2017
Biphenyls are an important intermediate in organic chemistry which constitutes the structural moiety of a wide range of compounds with profound pharmacological activity. Being a neutral molecule (due to absence of the active functional moiety on it), biphenyls are required to be functionalized i.e. introduction of active group on it. Thus, the substituted biphenyls can be used for synthesis or condensation of another active group with itself which are pharmacologically significant thereby forming the compounds with altogether new activity. Initially, biphenyls were widely used as intermediates in chemical synthesis and pesticides in the form of PCBs (polychlorinated biphenyls). But with the emerging trends in the synthetic chemistry, a number of derivatives are obtained which are of therapeutic significance. This review is summarized to know about synthesis of biphenyl and its derivatives as well as various biphenyl analogs that has potential to act against number of disease and disorders.
Angewandte Chemie International Edition, 2007
Devising novel multicomponent reactions (MCRs) that achieve the formation of multiple bonds in one operation is one of the major challenges in modern organic synthesis. [1] As such processes avoid time-consuming and costly purification processes, as well as protection-deprotection steps, they are inherently environmentally benign and atom economic. Whereas some powerful MCRs such as the Passerini and Ugi [4] reactions proceed in the absence of external reagents, most chemical transformations involve reactants that are not active enough to be self-assembled. Thus, the use of catalytic rather than stoichiometric amounts of external reagents to trigger the reaction is highly desirable to minimize the production of waste. As a continuation of our ongoing project on the development of palladium-catalyzed domino processes as well as direct CÀH functionalization, we report herein a palladium-catalyzed three-component synthesis of 3-(diarylmethylene)indolinones. The underlying principle of our approach is shown in Scheme 1. The Sonogashira coupling of N-aryl-N-alkyl propiolamides 1 with an aryl iodide 2 should give the phenyl propiolamide 5, which would then react with a second aryl halide 3, ideally in the presence of the same catalyst, to afford the target compound 4 through a sequence of intermolecular carbopalladation, C À H activation, and a C À C bond-forming process. Whereas many palladium-catalyzed transformations have been developed and widely used in novel domino processes for the syntheses of heterocycles, the MCR that combines mechanistically distinct reactions by a single catalyst is by far less developed owing to the specificity of each catalytic system to each individual reaction. To our knowledge, the use of a single palladium catalyst to catalyze three different reactions, namely aryl alkynylation, carbopal-ladation, and direct C À H functionalization, has not been reported previously. Very few examples have been reported that deal with the successful Sonogashira reaction of electron-deficient alkynes, such as propiolic esters and propiolamide, [22] with aryl halides. Despite this potential pitfall, we performed a survey of reaction conditions using N-(4-methoxyphenyl)-N-methyl propiolamide (1 a), phenyl iodide (2 a), and 2-nitrophenyliodide (3 a) as test substrates. In the event, stirring a solution of 1 a and 2 a in N,N-dimethylformamide (DMF) in the presence of [Pd(PPh 3 ) 4 ] (5 mol %), copper iodide (15 mol %), and Et 3 N at 60 8C for 1 h followed by addition of 3 a and heating to 110 8C for 15 h afforded the expected oxindole 4 a in 28 % yield. Control experiments indicated that a) Sonogashira coupling between 1 a and 2 a, the presumed first step of this domino process, proceeded smoothly to furnish the phenylpropiolamide 5 a in over 90 % yield, b) copper iodide is required for the successful Sonogashira coupling between 1 a and 2 a, and c) the Sonogashira coupling between 1 a and 2 a proceeded sluggishly under ligand-free conditions, although such conditions were of choice for the carbopalladation/C À H functionalization step. With these results in hand, we set out to focus on the overall reaction efficiency of this novel threecomponent reaction instead of optimizing the individual steps by varying the palladium source, the ligand, the amount of copper, the base, and the solvent. The results are summarized in .