Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• –111 (Figure 19; [20]). In contrast to a typical synthetic approach to diimidazoles as shown in Scheme 1, we used 4,5-dicyanoimidazole derivatives 1–3 (Scheme 2) and modern direct arylation, Suzuki–Miyaura, Sonogashira, and Heck reactions to construct molecules 101–111. These chromophores possess two

• very interested in the Heck coupling of N-alkyl vinazenes with various (hetero)aromates [115]. This synthetic interest resulted in four new diimidazole compounds 112–115 (Figure 20). This series of basic π-conjugated compounds was significantly extended in 2009 by a library of various π-linkers [116

A novel and facile synthesis of 3-(2-benzofuroyl)- and 3,6-bis(2-benzofuroyl)carbazole derivatives

• Wentao Gao,
• Meiru Zheng and
• Yang Li

Beilstein J. Org. Chem. 2011, 7, 1533–1540, doi:10.3762/bjoc.7.180

• presence of fluorine, chlorine, or bromine substituents (entries 6–11) is not problematic, thereby providing a potential handle for further functionalization (eg., Heck and Suzuki–Miyaura reactions) of the corresponding products 3f–k. In the cases of entries 9–11, the tert-butyl-substituted products 3i–k

Synthesis and oxidation of some azole-containing thioethers

• Andrei S. Potapov,
• Nina P. Chernova,
• Vladimir D. Ogorodnikov,
• Tatiana V. Petrenko and
• Andrei I. Khlebnikov

Beilstein J. Org. Chem. 2011, 7, 1526–1532, doi:10.3762/bjoc.7.179

• been reported, and some of them were found to be effective inhibitors of steel corrosion [2], while their chromium(III) and palladium(II) complexes demonstrated catalytic activity in ethylene oligomerization [3] and Heck cross-coupling reactions [4]. Recently we and others have reported high superoxide

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• conditions, one diastereomer was cleanly and completely transformed into the other one (Scheme 11) [10]. Hallberg and coworkers developed a one-pot strategy towards the synthesis of masked 3-aminoindan-1-ones 23. This process was initiated by Heck addition of an aryl triflate to a vinyl ether, leading to an

• used. A proper choice of catalyst and reaction conditions is also needed to improve the efficiency of each reaction (Scheme 18) [18]. Consecutive one-pot transformations initiated by Heck reaction and terminated by intramolecular aza–Michael addition were developed by Hanson and coworkers to access a

• , and catalytic Pd2(dba)3·CHCl3 led to the production of the desired sultams 42 upon heating at 110 °C. A series of sultam derivatives of bioactive, related isoindol-1-one amides 43 were also prepared by entering acrylic acid into the Heck–aza–Michael process and coupling a second amine derivative

Evaluation of a commercial packed bed flow hydrogenator for reaction screening, optimization, and synthesis

• Marian C. Bryan,
• David Wernick,
• Christopher D. Hein,
• James V. Petersen,
• John W. Eschelbach and
• Elizabeth M. Doherty

Beilstein J. Org. Chem. 2011, 7, 1141–1149, doi:10.3762/bjoc.7.132

• (Figure 7). It should be noted that Kappe observed a “Pd mirror” due to soluble Pd leaching from a CatCart® during a continuous flow Mizorki–Heck reaction [24]. In comparison, the fine black precipitate seen in our wash experiment is more consistent with solid Pd/C catalyst. The experiment was repeated

A practical two-step procedure for the preparation of enantiopure pyridines: Multicomponent reactions of alkoxyallenes, nitriles and carboxylic acids followed by a cyclocondensation reaction

• Christian Eidamshaus,
• Roopender Kumar,
• Mrinal K. Bera and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2011, 7, 962–975, doi:10.3762/bjoc.7.108

• nonaflates are excellent coupling partners in palladium-catalyzed transformations such as Suzuki, Stille, Heck and Sonogashira reactions [45]. However, in contrast to the smooth nonaflation, the selective O-alkylation of the synthesized pyridines turned out to be more challenging (Scheme 5). Whereas pyridone

Synthesis, reactivity and biological activity of 5-alkoxymethyluracil analogues

• Lucie Brulikova and
• Jan Hlavac

Beilstein J. Org. Chem. 2011, 7, 678–698, doi:10.3762/bjoc.7.80

• monophosphates. Almost 10 years earlier, Bergstrom and co-workers published a synthesis based on the same reaction – the Heck cross-coupling reaction of an alkene with an organometallic derivative [41] in which two pyrimidine nucleosides were coupled (Scheme 27). Thus, 5-(chloromercuri)-2'-deoxyuridine was

Synthesis of chiral mono(N-heterocyclic carbene) palladium and gold complexes with a 1,1'-biphenyl scaffold and their applications in catalysis

• Lian-jun Liu,
• Feijun Wang,
• Wenfeng Wang,
• Mei-xin Zhao and
• Min Shi

Beilstein J. Org. Chem. 2011, 7, 555–564, doi:10.3762/bjoc.7.64

• '-biphenyl backbone have been prepared from chiral 6,6'-dimethoxybiphenyl-2,2'-diamine. The complexes were characterized by X-ray crystal structure diffraction. The Pd(II) complex showed good catalytic activities in the Suzuki–Miyaura and Heck–Mizoroki coupling reactions, and the (S)-Au(I) complexes also

• showed good catalytic activities in the asymmetric intramolecular hydroamination reaction to give the corresponding product in moderate ee. Keywords: chiral mono(N-heterocyclic carbene) complex; Heck–Mizoroki reaction; hydroamination; Suzuki–Miyaura reaction; Introduction N-heterocyclic carbene (NHC

• coupling reactions and a Au-catalyzed asymmetric reaction, respectively. Suzuki–Miyaura and Heck–Mizoroki coupling reactions catalyzed by NHC–Pd(II) complex The Pd-catalyzed coupling reaction is one of the most powerful methods for the formation of carbon–carbon bonds in organic synthesis [60][61][62][63

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• [56] and also demonstrated that the meta photocycloaddition products containing a methoxy group at position 1 can be converted in a Heck-type reaction [57][58]. The intermediate palladium σ-complex, formed by insertion, opens the cyclopropane ring and arylated bicyclo[3.2.1]octane derivatives are

Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

• Bernhard Gutmann,
• Toma N. Glasnov,
• Tahseen Razzaq,
• Walter Goessler,
• Dominique M. Roberge and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2011, 7, 503–517, doi:10.3762/bjoc.7.59

• publication we reported the Mizoroki–Heck coupling of 4-iodobenzonitrile (12) with n-butyl acrylate (13) under high-temperature continuous flow conditions (150–190 °C) employing Pd(OAc)2 as a homogeneous pre-catalyst and a stainless steel-based coil flow system (Scheme 4) [59]. With only 0.01 mol % of Pd(OAc

• extensive washing regime with pure solvent. This became very obvious, since running the Mizoroki–Heck coupling shown in Scheme 4 without any added Pd catalyst still led to complete conversion in subsequent flow experiments utilizing the same coil. Control experiments in batch mode confirmed that the

• untreated steel material itself (SX 316L) cannot catalyze Mizoroki–Heck couplings of this type, despite of the fact that Ni and even Fe-catalyzed carbon–carbon bond forming reactions are well known in the literature [60][61]. Furthermore, very low levels of conversion were obtained in this coupling when

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• sulfonamides, all prepared in high yields. As this route employs sulfonamide-stabilised anions the preparation and handling of unstable sulfonyl chloride intermediates is therefore circumvented (Scheme 14) [17]. An analogous Heck reaction approach has also been employed to introduce a homologous side chain as

• chain is then reduced simultaneously with the complete reduction of the Cbz-group to a methyl group with lithium aluminium hydride. Finally, the sulfonate side chain is introduced via a Heck-type coupling similar to that of naratriptan (Scheme 15), followed by hydrogenation of the double bond to afford

• eletriptan (Scheme 20). A rather ingenious Mitsunobu coupling reaction has been used to create a highly functionalised substrate 96 for an intramolecular Heck reaction resulting in a very short and succinct synthesis of eletriptan and related analogues 97 [29] (Scheme 21). Interestingly, it was found that

The preparation of 3-substituted-1,5-dibromopentanes as precursors to heteracyclohexanes

• Bryan Ringstrand,
• Martin Oltmanns,
• Jeffrey A. Batt,
• Aleksandra Jankowiak,
• Richard P. Denicola and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2011, 7, 386–393, doi:10.3762/bjoc.7.49

• % [17][38]. The downside to Method 1C is that an excess of Grignard reagent (3–4 equiv) is required; therefore, it is not economical with respect to the alkyl halide. Method 1D also uses glutaconate diester, which is reacted with an aryl iodide in the presence of Pd(0) under Heck conditions. The

• prepared exclusively starting from tetrahydro-4H-pyran-4-one in overall yields averaging about 20% (three steps, entries 6 and 7). For comparison Table 2 includes the preparation of dibromides I (R = aryl) involving Heck-type arylation (entry 8) and dibromides I (R = alkyl) starting from tetrahydropyran-4

• -aryl derivatives, the most direct methods are the Heck-type coupling with glutaconate ester (Method 1D) and Suzuki-type coupling to 4-chlorotetrahydropyran (Method 2D). The preparation of dibromides I containing larger organic fragments from tetrahydropyrans VIII is inefficient and proceeds with low

Studies on Pd/NiFe₂O₄ catalyzed ligand-free Suzuki reaction in aqueous phase: synthesis of biaryls, terphenyls and polyaryls

• Sanjay R. Borhade and
• Suresh B. Waghmode

Beilstein J. Org. Chem. 2011, 7, 310–319, doi:10.3762/bjoc.7.41

• halides and the limited scope of the Suzuki reaction under ligand free conditions in the absence of additives thus faced with these limitations requires a fresh approach to carry out the Suzuki reaction. Recently, the use of Pd supported on surface-modified nano NiFe2O4 catalyst for the Heck and Suzuki

• reactions was demonstrated [40]. The most important paradigm of this reaction is the easy removal of catalyst from the reaction mixture by employing an external magnetic field. We recently reported the filtration-free magnetically separable Pd/NiFe2O4 catalyst for the Heck reaction [41]. Herein, we report

Total synthesis of (±)-coerulescine and (±)-horsfiline

• Mukund G. Kulkarni,
• Attrimuni P. Dhondge,
• Sanjay W. Chavhan,
• Ajit S. Borhade,
• Yunnus B. Shaikh,
• Deekshaputra R. Birhade,
• Mayur P. Desai and
• Nagorao R. Dhatrak

Beilstein J. Org. Chem. 2010, 6, 876–879, doi:10.3762/bjoc.6.103

• radical cyclizations [20][21][22][23][24], electrophilic cyclization [25], asymmetric nitroolefination reaction [26], palladium asymmetric allylic alkylation [27], palladium-catalyzed domino Heck–cyanation [28], Pd-catalyzed intramolecular cyanoamidation [29][30], NHC-mediated O- to C-carboxyl transfer

Conjugated polymers containing diketopyrrolopyrrole units in the main chain

• Bernd Tieke,
• A. Raman Rabindranath,
• Kai Zhang and
• Yu Zhu

Beilstein J. Org. Chem. 2010, 6, 830–845, doi:10.3762/bjoc.6.92

• polycondensation reactions such as Suzuki [17], Stille [18] and Heck [19] coupling are especially useful. Other suitable reactions are Ni-mediated Yamamoto coupling [20], Sonogashira coupling [21], or electrochemical polymerization [22]. In the following, a brief review of recently prepared DPP based polymers is

• number of studies were reported on synthesis, optical, electrochemical, and electroluminescent properties of conjugated DPP polymers. The polymers were prepared by Suzuki, Heck, and Stille coupling and other catalytic polycondensation reactions. Typical examples are shown in Scheme 2. Rabindranath et al

• rather weak (Φ ~15–35%), the maximum appeared at about 700–720 nm in the solid state. By Heck coupling it was possible to synthesize a polyarylenevinylene-type polymer P-13, the arylene units alternatingly being phenylenevinylene and diphenylDPP (Table 2) [36]. The polymer was obtained upon Pd-catalyzed

Pd-catalyzed decarboxylative Heck vinylation of 2-nitrobenzoates in the presence of CuF₂

• Lukas J. Gooßen,
• Bettina Zimmermann and
• Thomas Knauber

Beilstein J. Org. Chem. 2010, 6, No. 43, doi:10.3762/bjoc.6.43

• Lukas J. Goossen Bettina Zimmermann Thomas Knauber Department of Chemistry, Organic Chemistry, Technische Universität Kaiserslautern, Erwin-Schrödinger-Strasse, Geb. 54, D-67663 Kaiserslautern, Germany 10.3762/bjoc.6.43 Abstract A new protocol for the decarboxylative Heck vinylation of benzoic

• arenes in good yields. Keywords: carboxylic acids; copper; decarboxylation; Heck vinylation; palladium; Introduction The palladium-catalyzed coupling of olefins with aryl or vinyl substrates, developed by Mizoroki [1] and Heck [2][3] in the 1970s, is one of the most important, reliable and generally

• ][12], diazonium salts [13][14], arylsulfonyl halides [15] and aroyl chlorides [16] have also been used. Several protocols were recently described that draw on widely available carboxylic acid derivatives as alternative aryl sources. This not only extended the substrate basis of Heck reactions, but

Solvent-free and time-efficient Suzuki–Miyaura reaction in a ball mill: the solid reagent system KF–Al₂O₃ under inspection

• Franziska Bernhardt,
• Ronald Trotzki,
• Tony Szuppa,
• Achim Stolle and
• Bernd Ondruschka

Beilstein J. Org. Chem. 2010, 6, No. 7, doi:10.3762/bjoc.6.7

• comminuting the reactants for just 10 min [40][41] without the presence of any additional stabilizing or activating ligands. Compared to the original published procedure for the Suzuki–Miyaura reaction [36] or the protocols featured by Mack and Frejd and their coworkers for Sonogashira [54] and Heck–Jeffery

Diastereoselective functionalisation of benzo-annulated bicyclic sultams: Application for the synthesis of cis-2,4-diarylpyrrolidines

• Susan Kelleher,
• Pierre-Yves Quesne and
• Paul Evans

Beilstein J. Org. Chem. 2009, 5, No. 69, doi:10.3762/bjoc.5.69

• Scheme 1, a Heck (Heck–Mizoroki) cyclisation [5][6][7][8][9] was employed to form the cyclic sulfonamide. Subsequently, it was shown that high stereofacial bias was achieved on hydrogenation, generating 2 as a single diastereoisomer. Treatment under dissolved metal reduction conditions afforded the cis

• and 6b which were used as substrates for the N–S and C–S bond cleavage forming arylsubstituted pyrrolidines [1][2][3]. In relation to this sequence attempts to achieve a reductive Heck cyclisation employing ammonium formate [12], gave only the product of bromine-hydrogen exchange 4c (where X = H

• ). Therefore, a one-pot method was developed based on recent reports which demonstrate that the residual palladium catalyst in Heck reactions may effectively mediate the addition of hydrogen to the newly substituted alkene [13][14][15]. Thus, following complete Heck cyclisation, as judged by TLC analysis, the

Gold film- catalysed benzannulation by Microwave- Assisted, Continuous Flow Organic Synthesis (MACOS)

• Gjergji Shore,
• Michael Tsimerman and
• Michael G. Organ

Beilstein J. Org. Chem. 2009, 5, No. 35, doi:10.3762/bjoc.5.35

• Suzuki–Miyaura and Heck reactions, i.e., Pd-thin films promote these transformations without any additional catalyst being added to the reactant stream(s) that enter the flow tube [28]. Without microwave irradiation, the above-described cross-coupling reactions did not proceed indicating that there is

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• the C10 hydroxymethyl to complete the mitomycin carbon backbone (Scheme 56). However, compound 206 was very unstable with a half-life of 1.5 days at −15 °C. 7.2. Rapoport. Intramolecular Heck coupling In 1983 Rapoport released a fascinating synthesis of aziridinomitosenes based on a photochemical

• oxidation and an intramolecular Heck reaction [149]. Exposure of the quinone 207 to sunlight triggered the formation of benzoxazole 208, which cleaved to form an intermediate iminium salt. Subsequent proton transfer gave the vinylogous carbamate 209 (Scheme 57). After oxidation of the hydroquinone to the

• unnatural regioisomer 214 as the major product. Because carbon C2 in quinone 211 is more electrophilic than carbon C1, nucleophilic addition-elimination of vinylogous carbamate 212 at the carbon centre gave intermediate 213 which cyclized in situ to give compound 214. 7.3. Michael. Intramolecular Heck

From discovery to production: Scale- out of continuous flow meso reactors

• Peter Styring and
• Ana I. R. Parracho

Beilstein J. Org. Chem. 2009, 5, No. 29, doi:10.3762/bjoc.5.29

• Suzuki and Heck coupling reactions at elevated temperatures while the nickel catalyst is active in the Kumada coupling [11][12] reaction at room temperature in batch (Scheme 1) and continuous flow reactors. In the latter, the catalyst is packed into a 3 mm diameter glass reactor tube of length 25 mm and

Synthesis of novel photochromic pyrans via palladium- mediated reactions

• Christoph Böttcher,
• Gehad Zeyat,
• Saleh A. Ahmed,
• Elisabeth Irran,
• Thorben Cordes,
• Cord Elsner,
• Wolfgang Zinth and
• Karola Rueck-Braun

Beilstein J. Org. Chem. 2009, 5, No. 25, doi:10.3762/bjoc.5.25

• rearrangement reactions [25]. Since nitriles are important intermediates in the synthesis of carboxylic acids and derivatives, and for the introduction of aminomethyl substituents, we started our studies with palladium-catalyzed cyanation reactions. The studies were then extended towards a Heck carbonylation in

• in good to excellent yields (Scheme 6). Starting from the bromo-substituted pyran 2b a final carbonylation step (Scheme 6) would directly complete the synthesis of an Fmoc-protected ω-amino acid. Though many protocols for Heck carbonylations are known, only a few report neutral reaction conditions

Polyionic polymers – heterogeneous media for metal nanoparticles as catalyst in Suzuki–Miyaura and Heck–Mizoroki reactions under flow conditions

• Klaas Mennecke and
• Andreas Kirschning

Beilstein J. Org. Chem. 2009, 5, No. 21, doi:10.3762/bjoc.5.21

• heterogeneous supports for palladium(0) nanoparticles is described. These functionalized polymers were incorporated inside a flow reactor and employed in Suzuki–Miyaura and Heck cross couplings under continuous flow conditions. Keywords: Heck–Mizoroki reaction; heterogeneous catalysis; ion exchange resin

• 0.7 ppm for each run. This very low value for leaching corresponds to the leaching determined for transfer hydrogenations with this catalytic flow system using cyclohexene as hydrogen source and solvent [23][24]. Heck–Mizoroki reactions One other very important cross coupling reaction that bears

• industrial relevance is the Heck–Mizoroki reaction. We were able to perform C-C coupling reaction under flow conditions with aryl iodides 23–28 using catalyst 3 (Table 2). Optimization of the conditions for our monolithic flow reactor was conducted with 4′-iodoacetophenone (23) and styrene (29) as coupling

Convenient methods for preparing π-conjugated linkers as building blocks for modular chemistry

• Jiří Kulhánek,
• Filip Bureš and
• Miroslav Ludwig

Beilstein J. Org. Chem. 2009, 5, No. 11, doi:10.3762/bjoc.5.11

• ] proved to be infeasible. However, in light of the report by Itami and Yoshida [34], we attempted the Mizoroki–Heck C–H arylation of 4-bromo-N,N-dimethylaniline with an equimolar amount of vinylboronate pinacol ester leading to the desired 3c in 73% yield (Scheme 1, Method A). 4-Substituted 4

• . Overall 12 extended π-linkers have been easily synthesized (8 of them are new compounds) utilizing procedures such as a lithiation/reaction with triisopropyl borate/esterification with pinacol, Mizoroki–Heck coupling with vinylboronate pinacol ester, borylation with bis(pinacolato)diboron or Sonogashira

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48