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1.
A surprisingly mild and versatile method for palladium-catalyzed Suzuki cross-couplings of aryl chlorides in the presence of a triarylphosphine 总被引:1,自引:0,他引:1
In the presence of new air-stable triarylphosphine 2, palladium-catalyzed Suzuki reactions of a wide array of aryl chlorides can be accomplished in uniformly good yield, including couplings of very sterically demanding and electronically deactivated substrates; activated aryl chlorides can be coupled at room temperature. In terms of scope and mildness, Pd-2 compares well with other catalyst systems that have been described for Suzuki reactions of aryl chlorides, thereby establishing that triarylphosphines should be regarded as fertile ground for future ligand-design efforts for palladium-catalyzed couplings of aryl chlorides. 相似文献
2.
An in silico study examined the stabilities of hydrogen-bonded complexes between simple thiourea catalysts and three different electrophiles and identified a novel, highly active N-tosyl urea catalyst for the promotion of addition reactions to epoxide electrophiles. Synthesis and evaluation of 6 revealed it to be a powerful catalyst for the addition of 1,2-dimethylindole to styrene oxide under conditions in which simple N,N-bis-aryl ureas and thioureas (including 1) are inactive. Subsequent studies determined 6 to be compatible with a range of indole and epoxide substrates (including (E)-stilbene oxide) and found that relatively poor nucleophiles such as sterically and electronically deactivated anilines, thiophenol, and benzyl alcohol could be efficiently and regioselectively added to oxiranes under mild conditions. 相似文献
3.
Bolliger JL Blacque O Frech CM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(26):7969-7977
The aminophosphine-based pincer complexes [C6H3-2,6-(XP(piperidinyl)2)2Pd(Cl)] (X=NH 1; X=O 2) are readily prepared from cheap starting materials by sequential addition of 1,1',1'-phosphinetriyltripiperidine and 1,3-diaminobenzene or resorcinol to solutions of [Pd(cod)(Cl)2] (cod=cyclooctadiene) in toluene under N2 in "one pot". Compounds 1 and 2 proved to be excellent Heck catalysts and allow the quantitative coupling of several electronically deactivated and sterically hindered aryl bromides with various olefins as coupling partners at 140 degrees C within very short reaction times and low catalyst loadings. Increased reaction temperatures also enable the efficient coupling of olefins with electronically deactivated and sterically hindered aryl chlorides in the presence of only 0.01 mol % of catalyst. The mechanistic studies performed rule out that homogeneous Pd 0 complexes are the catalytically active forms of 1 and 2. On the other hand, the involvement of palladium nanoparticles in the catalytic cycle received strong experimental support. Even though pincer-type Pd IV intermediates derived from 1 (and 2) are not involved in the catalytic cycle of the Heck reaction, their general existence as reactive intermediates (for example, in other reactions) cannot be excluded. On the contrary, they were shown to be thermally accessible. Compounds 1 and 2 show a smooth halide exchange with bromobenzene to yield their bromo derivatives in DMF at 100 degrees C. Experimental observations revealed that the halide exchange most probably proceeded via pincer-type Pd IV intermediates. DFT calculations support this hypothesis and indicated that aminophosphine-based pincer-type Pd IV intermediates are generally to be considered as reactive intermediates in reactions with aryl halides performed at elevated temperatures. 相似文献
4.
《Tetrahedron letters》2019,60(34):150970
The I2 mediated desulfurization of N,N′-di-Boc-thiourea was developed. Various primary amines, including sterically and electronically deactivated primary amines, were transformed into the corresponding bis-Boc protected guanidines under mild conditions. 相似文献
5.
Electrophilic Formylation of Arenes by Silylium Ion Mediated Activation of Carbon Monoxide
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Lukas Omann Dr. Zheng‐Wang Qu Dr. Elisabeth Irran Dr. Hendrik F. T. Klare Prof. Dr. Stefan Grimme Prof. Dr. Martin Oestreich 《Angewandte Chemie (International ed. in English)》2018,57(27):8301-8305
Arene‐stabilized silylium ions react with carbon monoxide rather than carbon monoxide adducts of silylium ions reacting with arenes. This mechanism is supported by quantum‐chemical calculations. Even sterically hindered mesitylene and electronically deactivated chlorobenzene engage in this electrophilic aromatic substitution. The silylium ion mediated formylation corresponds to Gattermann–Koch reactions promoted by strong Brønsted acids. The resulting silylcarboxonium ion of the arenecarbaldehyde was crystallographically characterized, for the first time revealing the molecular structure of this synthetically important intermediate. 相似文献
6.
Jeanne L. Bolliger Christian M. Frech Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(13):4075-4081
Dichloro‐bis(aminophosphine) complexes are stable depot forms of palladium nanoparticles and have proved to be excellent Suzuki–Miyaura catalysts. Simple modifications of the ligand (and/or the addition of water to the reaction mixture) have allowed their formation to be controlled. Dichlorobis[1‐(dicyclohexylphosphanyl)piperidine]palladium ( 3 ), the most active catalyst of the investigated systems, is a highly convenient, reliable, and extremely active Suzuki catalyst with excellent functional group tolerance that enables the quantitative coupling of a wide variety of activated, nonactivated, and deactivated and/or sterically hindered functionalized and heterocyclic aryl and benzyl bromides with only a slight excess (1.1–1.2 equiv) of arylboronic acid at 80 °C in the presence of 0.2 mol % of the catalyst in technical grade toluene in flasks open to the air. Conversions of >95 % were generally achieved within only a few minutes. The reaction protocol presented herein is universally applicable. Side‐products have only rarely been detected. The catalytic activities of the aminophosphine‐based systems were found to be dramatically improved compared with their phosphine analogue as a result of significantly faster palladium nanoparticle formation. The decomposition products of the catalysts are dicyclohexylphosphinate, cyclohexylphosphonate, and phosphate, which can easily be separated from the coupling products, a great advantage when compared with non‐water‐soluble phosphine‐based systems. 相似文献
7.
Aurpon W. Mitra Marvin M. HansenMichael E. Laurila Stanley P. KolisJoseph R. Martinelli 《Tetrahedron letters》2013
α-Aminoamides are shown to be useful as ligands in Goldberg amidations. A number of α-aminoamides are examined and the importance of substitution on the α-aminoamides is explored. Acetamide is focused on as the nucleophilic coupling partner due to its low cost, stability and convenience as a protecting group. The initial substrate scope for these catalysts is explored and includes electronically activated and deactivated aryl bromides, however o-substituted aryl bromides are problematic. 相似文献
8.
Scope and limitations of Pd2(dba)3/P(i-BuNCH2CH2)3N-catalyzed Buchwald-Hartwig amination reactions of aryl chlorides 总被引:2,自引:0,他引:2
Proazaphosphatrane ligands in combination with Pd(2)(dba)(3) generate highly active catalysts for Buchwald-Hartwig amination of aryl chlorides. In particular, commercially available P(i-BuNCH(2)CH(2))(3)N is a highly general and efficient ligand, allowing the coupling of an electronically diverse set of aryl chlorides, including chloropyridines, with a wide variety of amines using 1 mol % of Pd at 100 degrees C. Either a 1:1 or 2:1 ratio of ligand to Pd was found to be effective. This catalyst system performs exceptionally well for sterically hindered substrates, even with only 0.25 mol % of Pd. It is shown that NaOH can also be used as the base (instead of NaO-t-Bu) allowing functionalized substrates to participate in these reactions. 相似文献
9.
A novel amide-assisted rearrangement reaction of hydroxybenzimidoyl chloride has been established for the efficient synthesis of 1,3-diphenylurea derivatives. A variety of electronically and sterically different 1,3-diphenylurea derivatives can be obtained in good to excellent yields, and a proposed reaction mechanism is also presented. 相似文献
10.
Surampudi SK Nagarjuna G Okamoto D Chaudhuri PD Venkataraman D 《The Journal of organic chemistry》2012,77(4):2074-2079
We describe a synthetic protocol to selectively functionalize chiral bridged triarylamines at the apical position using regioselective copper-catalyzed amination reaction. This protocol allows the coupling of diphenylamines with a sterically hindered but electronically activated aryl-Br bond in the presence of a sterically unhindered but electronically unactivated aryl-Br bond. The unactivated aryl-Br bond was utilized further to synthesize a chiral heterohelicene homodimer using Stille coupling. 相似文献
11.
Alberto Scrivanti Valentina Beghetto Simonetta Antonaroli Federica Mandoj Bruno Crociani 《Tetrahedron letters》2004,45(30):5861-5864
The iminophosphine-palladium(0) complex [Pd(dmfu)(P-N)] [dmfu=dimethyl fumarate; P-N=2-(PPh2)C6H4-1-CHNC6H4-4-OMe] is a very efficient catalyst for the Suzuki coupling. In the reaction of aryl bromides with phenylboronic acid, turnover numbers up to ca. 200,000 are obtained at 110 °C in 2 h. Good rates are obtained also with the sterically hindered and electronically deactivated 2-bromo-1,3,5-trimethylbenzene. The complex is able to catalyze the exhaustive arylation of 2,3,7,8,12,13,17,18-octabromo-5,10,15-triphenylcorroleCu(III) to yield the corresponding undecaaryl substituted derivative. 相似文献
12.
Jonathan R. Carney Barry R. Dillon Leonie Campbell Dr. Stephen P. Thomas 《Angewandte Chemie (International ed. in English)》2018,57(33):10620-10624
The manganese‐catalyzed hydrosilylation and hydroboration of alkenes has been developed using a single manganese(II) precatalyst and reaction protocol. Both reactions proceed with excellent control of regioselectivity and in high yields across a variety of sterically and electronically differentiated substrates (25 examples). Alkoxide activation, using NaOtBu, was key to precatalyst activation and reactivity. Catalysis was achieved across various functional groups and on gram‐scale for both the developed methodologies with catalysts loadings as low as 0.5 mol %. 相似文献
13.
[reaction: see text] A range of peptoids can be prepared efficiently using microwave-assisted solid-phase chemistry in a commercial reactor. This method is most effective for the installation of electronically deactivated benzylic amines. The systematic incorporation of these amines into peptoids can deliver oligomers capable of displaying unique and stable structural motifs-microwave-assisted solid-phase synthesis will enable their future study and application. 相似文献
14.
Kawamorita S Ohmiya H Iwai T Sawamura M 《Angewandte Chemie (International ed. in English)》2011,50(36):8363-8366
Immobile but active: A silica-supported "compact" phosphane, Silica-SMAP, can be used in the Pd-catalyzed borylation of aryl chlorides or bromides with bis(pinacolato)diboron. The Silica-SMAP/Pd system significantly expands the substrate scope of the borylation toward sterically and electronically challenging aryl halides. 相似文献
15.
Devendrapratap U Singh 《Tetrahedron letters》2004,45(24):4805-4807
Fe-exchanged montmorillonite K10 catalyzes a highly efficient reaction between sterically and electronically diverse sulfonamides and carboxylic acid anhydrides to furnish N-acylsulfonamides in excellent yield and high selectivity. The catalyst can also be reused several times. 相似文献
16.
17.
Schaper LA Öfele K Kadyrov R Bechlars B Drees M Cokoja M Herrmann WA Kühn FE 《Chemical communications (Cambridge, England)》2012,48(32):3857-3859
A new ammonia adduct of a N-heterocyclic carbene (NHC) has been isolated, which can be used as a reagent for the synthesis of transition metal carbene complexes. It represents the first example of a 1,2,3-triazolylidene with a 1,2,4-substitution pattern, thus opening a new subclass ('normal' 1,2,3-triazolylidenes) of sterically and electronically tunable NHCs. 相似文献
18.
Qingfa Wang Li Wang Yaquan Wang Fei He Zhenhua Li Zhentao Mi 《Reaction Kinetics and Catalysis Letters》2004,81(2):297-304
Deactivated palladium catalysts in the hydrogenation of anthraquinione were regenerated with ethanol, nitric acid, hydrogen
peroxide, boiling water and steam, respectively. The deactivated and regenerated catalysts were characterized by XPS, ICP,
TG, FTIR, TPD, XRD, etc., and studied in the hydrogenation of anthraquinone. The results showed that the main cause of catalyst deactivation is the
coverage of the active component by deposits. The treatments by hydrogen peroxide and boiling water can effectively regenerate
the deactivated catalysts.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
Douglas W. Crandell Shivnath Mazumder P. Andrew Evans Mu-Hyun Baik 《Chemical science》2015,6(12):6896-6900
Density functional theory calculations demonstrate that the reversal of regiochemical outcome of the addition for substituted methyl propiolates in the rhodium-catalyzed [(2 + 2) + 2] carbocyclization with PPh3 and (S)-xyl-binap as ligands is both electronically and sterically controlled. For example, the ester functionality polarizes the alkyne π* orbital to favor overlap of the methyl-substituted terminus of the alkyne with the pπ-orbital of the alkenyl fragment of the rhodacycle during alkyne insertion with PPh3 as the ligand. In contrast, the sterically demanding xyl-binap ligand cannot accommodate the analogous alkyne orientation, thereby forcing insertion to occur at the sterically preferred ester terminus, overriding the electronically preferred orientation for alkyne insertion. 相似文献