Carbon–carbon bond cleavage for Cu-mediated aromatic trifluoromethylations and pentafluoroethylations

• Tsuyuka Sugiishi,
• Hideki Amii,
• Kohsuke Aikawa and
• Koichi Mikami

Beilstein J. Org. Chem. 2015, 11, 2661–2670, doi:10.3762/bjoc.11.286

• the decarboxylative trifluoromethylation of aryl halides [37] (Scheme 4). Not only iodobenzene but also 4-bromotoluene was trifluoromethylated by the [(NHC)Cu(TFA)] complex. The perfluoroalkylation reactions mentioned above require a stoichiometric amount of copper reagent, whereas it was found that

• the addition of silver salts is effective for the copper-mediated trifluoromethylation of aryl iodides [38] (Scheme 5). The amount of copper used in the reaction was reduced to 30 or 40 mol % by adding a small amount of Ag2O. As a related decarboxylative transformation, silver-mediated aromatic

• trifluoromethylation of aryl iodides with ClCF2CO2Me and fluoride can be utilized for clinical studies. Herein, we introduce one example of decarboxylative [18F]trifluoromethylation for positron emission tomography (PET) studies. A synthetic methodology for [18F]labelled-CF3 arenes is desired for the application of

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• , cyclic amines were produced. Carboxylic acids were particularly fruitful affording C-centered radicals that alkylated alkenes and took part in tandem addition cyclizations producing chromenopyrroles; decarboxylative homo-dimerizations were also observed. Acceptors initially yielding radical anions

• components, decarboxylative arylations of amino acids, diastereoselective preparations of cis-cyclobutanes via [2 + 2] cycloadditions of enones, selective reductions of benzylic and α-carbonyl halides and, with fac-Ir(ppy)3, reductions of unactivated alkyl iodides [5][6][7][8]. Furthermore, the value of

• functionalized carboxylic acids that take part in decarboxylative additions to maleimides is presented in Scheme 5. Reasonable yields of adducts were obtained for alkyl radicals with α-alkoxy substituents. Two diastereomers of 22 as a 1:1 mixture were obtained from 2-tetrahydrofuroic acid in a very pleasing

Radical-mediated dehydrative preparation of cyclic imides using (NH₄)₂S₂O₈–DMSO: application to the synthesis of vernakalant

• Dnyaneshwar N. Garad,
• Subhash D. Tanpure and
• Santosh B. Mhaske

Beilstein J. Org. Chem. 2015, 11, 1008–1016, doi:10.3762/bjoc.11.113

• persistent interest [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. Results and Discussion While working on the development of a palladium-catalyzed decarboxylative C–H activation methodology to access the important core structure dihydroquinolone

Sequential decarboxylative azide–alkyne cycloaddition and dehydrogenative coupling reactions: one-pot synthesis of polycyclic fused triazoles

• Kuppusamy Bharathimohan,
• Thanasekaran Ponpandian,
• A. Jafar Ahamed and
• Nattamai Bhuvanesh

Beilstein J. Org. Chem. 2014, 10, 3031–3037, doi:10.3762/bjoc.10.321

• describe a one-pot protocol for the synthesis of a novel series of polycyclic triazole derivatives. Transition metal-catalyzed decarboxylative CuAAC and dehydrogenative cross coupling reactions are combined in a single flask and achieved good yields of the respective triazoles (up to 97% yield). This

• methodology is more convenient to produce the complex polycyclic molecules in a simple way. Keywords: copper(II) acetate; decarboxylative CuAAC; dehydrogenative coupling; fused triazoles; one-pot synthesis; Introduction The copper-catalyzed Huisgen [3 + 2] cycloaddition (or copper-catalyzed azide–alkyne

• cycloaddition, CuAAC) between an organic azide and a terminal alkyne is a well-established strategy for the construction of 1,4-disubstituted 1,2,3-triazoles [1][2][3][4]. In a recent development, this decarboxylative coupling reaction was well documented for the generation of C–C bonds [5]. This method has

Formal total syntheses of classic natural product target molecules via palladium-catalyzed enantioselective alkylation

• Yiyang Liu,
• Marc Liniger,
• Ryan M. McFadden,
• Jenny L. Roizen,
• Jacquie Malette,
• Corey M. Reeves,
• Douglas C. Behenna,
• Masaki Seto,
• Jimin Kim,
• Justin T. Mohr,
• Scott C. Virgil and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2014, 10, 2501–2512, doi:10.3762/bjoc.10.261

• install the initial stereocenters (Scheme 3). Treatment of 16 with LiHMDS in THF, followed by allyl chloroformate, furnished the known carbonate 17 in high yield [34]. This substrate smoothly undergoes palladium-catalyzed enantioselective decarboxylative allylation in the presence of (S)-t-Bu-PHOX (5

• enantioenriched piperidinone 47, and thus a single enantiomer of rhazinilam may be prepared. The formal synthesis of (+)-rhazinilam commenced with palladium-catalyzed decarboxylative allylic alkylation of known carboxy-lactam 49 to afford benzoyl-protected piperidinone 50 in 97% yield and 99% ee (Scheme 11) [84

Facile synthesis of 1-alkoxy-1H-benzo- and 7-azabenzotriazoles from peptide coupling agents, mechanistic studies, and synthetic applications

• Mahesh K. Lakshman,
• Manish K. Singh,
• Mukesh Kumar,
• Raghu Ram Chamala,
• Vijayender R. Yedulla,
• Domenick Wagner,
• Evan Leung,
• Lijia Yang,
• Asha Matin and
• Sadia Ahmad

Beilstein J. Org. Chem. 2014, 10, 1919–1932, doi:10.3762/bjoc.10.200

• derivative under palladium-catalyzed conditions. The benzoyl ester of BtOH has been evaluated in a decarboxylative Pd-mediated Heck reaction, leading to a modest product yield [36]. However, this appears to be the only example of a BtOH derivative in Pd-mediated reactions. In principle, formation of π–allyl

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• rationalized using semi-empirical calculations. In the same contribution, the cascade reactions starting from uracil polyoxin C 106 were described (Scheme 44). Decarboxylative formation of azomethine ylides from 106 and an aldehyde (or ketone), followed by reaction of the ylide with maleimide afforded mixtures

A convenient enantioselective decarboxylative aldol reaction to access chiral α-hydroxy esters using β-keto acids

• Zhiqiang Duan,
• Jianlin Han,
• Ping Qian,
• Zirui Zhang,
• Yi Wang and
• Yi Pan

Beilstein J. Org. Chem. 2014, 10, 969–974, doi:10.3762/bjoc.10.95

• University, Nanjing, 210093, China 10.3762/bjoc.10.95 Abstract We show a convenient decarboxylative aldol process using a scandium catalyst and a PYBOX ligand to generate a series of highly functionalized chiral α-hydroxy esters. The protocol tolerates a broad range of β-keto acids with inactivated aromatic

• appears as a common procedure, affording chiral tertiary alcohols which are ubiquitous in the biological sciences and pharmaceutical industry [1][2][3][4][5][6]. The decarboxylative aldol reaction, broadly used for the generation of ester enolate equivalents by the promotion of releasing CO2, has become

• an appealing method to access chiral tertiary alcohols. Taking advantage of this rigid reactivity, several unique catalytic decarboxylative aldol transformations of β-keto acids with various protic aldehydes have been developed [7][8][9][10] (Figure 1). High enantioselectivities were achieved with

Practical synthesis of aryl-2-methyl-3-butyn-2-ols from aryl bromides via conventional and decarboxylative copper-free Sonogashira coupling reactions

• Andrea Caporale,
• Stefano Tartaggia,
• Andrea Castellin and
• Ottorino De Lucchi

Beilstein J. Org. Chem. 2014, 10, 384–393, doi:10.3762/bjoc.10.36

• solvent was found to be highly effective for the coupling reaction of 2-methyl-3-butyn-2-ol (4) with a wide range of aryl bromides in good to excellent yields. Analogously, the synthesis of aryl-2-methyl-3-butyn-2-ols was performed also through the decarboxylative coupling reaction of 4-hydroxy-4-methyl-2

• bromides rather than expensive iodides and using 4 or propiolic acid rather than TMS-acetylene as inexpensive alkyne sources are described. Keywords: alkynes; decarboxylative couplings; Erlotinib; palladium; propiolic acid; Introduction The Sonogashira coupling reaction of aryl or alkenyl halides with

• presence of a Cu/Pd bimetallic catalyst, followed by the basic cleavage of the protecting group [42][43][44][45][46]. Terminal alkynes are often used as starting materials for the synthesis of disubstituted acetylenes through a second coupling process with another aryl halide. Decarboxylative couplings

The regioselective synthesis of spirooxindolo pyrrolidines and pyrrolizidines via three-component reactions of acrylamides and aroylacrylic acids with isatins and α-amino acids

• Tatyana L. Pavlovskaya,
• Fedor G. Yaremenko,
• Victoria V. Lipson,
• Svetlana V. Shishkina,
• Oleg V. Shishkin,
• Vladimir I. Musatov and
• Alexander S. Karpenko

Beilstein J. Org. Chem. 2014, 10, 117–126, doi:10.3762/bjoc.10.8

• inhibitors [9][10]. The multicomponent 1,3-dipolar cycloaddition of azomethine ylides, generated in situ via decarboxylative condensation of isatins and α-amino acids with olefinic and acetylenic dipolarophiles, represents a key approach for the regio- and stereoselective construction of a variety of complex

• azomethine ylides, generated in situ via decarboxylative condensation of isatins and N-substituted α-amino acids (sarcosine, proline and thiazolidine-4-carboxilic acid) in a three-component fashion. Results and Discussion The three-component condensation of equimolar amounts of isatins 1, α-amino acids 2 and

• 22.9° and the shortest distance between carbon atoms (C6…C15) is 3.04 Å). The mechanism of the azomethine ylide formation by a decarboxylative route has been repeatedly described by a number of authors and is depicted in Scheme 1 [35][36]. The reaction between isatin and the α-amino acid affords the

The regulation and biosynthesis of antimycins

• Ryan F. Seipke and
• Matthew I. Hutchings

Beilstein J. Org. Chem. 2013, 9, 2556–2563, doi:10.3762/bjoc.9.290

• , suggesting that these strains produce antimycins with less chemical diversity at the R2 position (Figure 2 and Figure 3). The KS domain catalyses the decarboxylative condensation between the aminoacyl thioester attached to AntCT2 and the 2-carboxy-acyl moiety attached to AntDACP. Next, a discrete

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• decarboxylative fluoroalkylation (Table 1) [61]. A wide range of α,β-unsaturated carboxylic acids afforded the corresponding difluoromethylated alkenes in high yields and with excellent E/Z selectivity. The putative mechanism for this copper-catalyzed decarboxylative fluoro-alkylation involves the iodine–oxygen

• regenerates the copper catalyst, thus allowing the catalytic turnover (Figure 1). 2.2 Iron catalysis Similarly to the work of J. Hu and colleagues using copper catalysis, the group of Z.-Q. Liu reported on the decarboxylative difluoromethylation of α,β-unsaturated carboxylic acids. However, the latter used

• -unsaturated carboxylic acids. Carboxylic acids have often been reported as convenient reactants for metal-catalyzed decarboxylative cross-coupling reactions. The methodology developed by J. Hu et al. for the difluoromethylation of α,β-unsaturated carboxylic acids (section 2.1) has also been applied for the

Iron-catalyzed decarboxylative alkenylation of cycloalkanes with arylvinyl carboxylic acids via a radical process

• Jincan Zhao,
• Hong Fang,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2013, 9, 1718–1723, doi:10.3762/bjoc.9.197

• (acac)3-catalyzed decarboxylative coupling of 2-(aryl)vinyl carboxylic acids with cycloalkanes was developed by using DTBP as an oxidant through a radical process. This reaction tolerates a wide range of substrates, and products are obtained in good to excellent yields (71–95%). The reaction also shows

• excellent stereoselectivity, and only trans-isomers are obtained. Keywords: alkenylation; cycloalkanes; decarboxylative; Fe(acac)3; free radical; sp3 C–H bonds; Introduction Direct C–H functionalization has become one of the most useful and attractive tools in organic chemistry because it can construct

• cycloalkanes were prepared based on a radical substitution of cyclohydrocarbon units to (E)-β-nitrostyrenes by using the radical initiator benzoyl peroxide [59]. Recently, the Liu group developed a copper-catalyzed decarboxylative coupling of vinylic carboxylic acids with simple alcohols and ethers in high

Homolytic substitution at phosphorus for C–P bond formation in organic synthesis

• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 1269–1277, doi:10.3762/bjoc.9.143

• more reactive than a phenyltelluranyl radical. Substitution of halides (X), carboxys (COOR), or carboxylates (OCOR) with phosphorus After scattered research efforts into the uncontrolled radical C–H phosphination under harsh reaction conditions [40], Barton elegantly devised radical decarboxylative

• . Thiophosphination with S-thiophosphinyl O-ethyl dithiocarbonate. Photoinduced selenophosphination of allenes. Photoinduced tellurophosphination. Decarboxylative phosphorylation of carboxylic acid derivatives. Plausible mechanism of decarboxylative phosphorylation. Radical phosphination of PTOC esters with white

Quantification of N-acetylcysteamine activated methylmalonate incorporation into polyketide biosynthesis

• Stephan Klopries,
• Uschi Sundermann and
• Frank Schulz

Beilstein J. Org. Chem. 2013, 9, 664–674, doi:10.3762/bjoc.9.75

• Polyketides are biosynthesized through consecutive decarboxylative Claisen condensations between a carboxylic acid and differently substituted malonic acid thioesters, both tethered to the giant polyketide synthase enzymes. Individual malonic acid derivatives are typically required to be activated as coenzyme

• propionate starter unit with six equivalents of methylmalonyl-coenzyme A (MM-CoA). After six rounds of decarboxylative Claisen condensations and varying degrees of reduction of the initially formed β-keto thioesters, the polyketide core of erythromycin is released from the enzyme via a terminal esterase [6

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• acetone-sensitised photodecarboxylation chemistry initially developed by Griesbeck [58] under batch conditions was suggested as being ideally suited to microflow conditions [59][60]. The chemistry involves the decarboxylative addition of potassium carboxylates to phthalimides, thus offering an alternative

• ) allows the decarboxylative additions to be performed as intramolecular cyclisations to the heterocyclic systems 49 (Scheme 16). The reactions of both substrates proved successful in both batch and microflow reactors with the batch reactor proving the most productive (0.54 versus 0.02 mmol/h). When the

Organocatalytic C–H activation reactions

• Subhas Chandra Pan

Beilstein J. Org. Chem. 2012, 8, 1374–1384, doi:10.3762/bjoc.8.159

• disclosed examples of Brønsted acid catalysed decarboxylative redox-amination reactions. 2-Carboxyindoline and trans-4-hydroxyproline were used as the substrates, respectively [22][23]. Benzoic acid as catalyst and 1,4-dioxane as solvent was identified by the Pan group as the best system for the reaction

• ongoing. Conclusion In summary, this review highlights the recent developments of organocatalytic C–H activation reactions. Organocatalysts have been involved in 1,5-hydride shift and decarboxylative/non-decarboxylative redox-amination processes. Asymmetric organocatalytic C–H activation reactions have

• . Mechanism for the indole-annulation cascade reaction. Synthesis of N-alkylpyrroles and δ-hydroxypyrroles. Synthesis of N-alkylindoles 9 and N-alkylindolines 10. Mechanistic study for the N-alkylpyrrole formation. Benzoic acid catalysed decarboxylative redox amination. Organocatalytic redox reaction of ortho

Asymmetric organocatalytic decarboxylative Mannich reaction using β-keto acids: A new protocol for the synthesis of chiral β-amino ketones

• Chunhui Jiang,
• Fangrui Zhong and
• Yixin Lu

Beilstein J. Org. Chem. 2012, 8, 1279–1283, doi:10.3762/bjoc.8.144

• Chunhui Jiang Fangrui Zhong Yixin Lu Department of Chemistry & Medicinal Chemistry Program, Life Sciences Institute, National University of Singapore, 3 Science Drive 3, Republic of Singapore, 117543 10.3762/bjoc.8.144 Abstract The first decarboxylative Mannich reaction employing β-keto acids

• , catalyzed by cinchonine-derived bifunctional thiourea catalyst has been described. The desired β-amino ketones were obtained in excellent yields and with moderate to good enantioselectivities. Keywords: decarboxylative addition; β-keto acid; Mannich reaction; organocatalysis; Introduction Chiral β-amino

• unsatisfactory and the enantioselectivities were modest [20]. In recent years, inspired by the enzymatic synthesis of polyketides and fatty acids in biological systems, the enantioselective decarboxylative reactions of malonic acid half thioesters (MAHTs) have received much attention. In this regard, various

Palladium-catalyzed substitution of (coumarinyl)methyl acetates with C-, N-, and S-nucleophiles

• Kalicharan Chattopadhyay,
• Erik Fenster,
• Alexander J. Grenning and
• Jon A. Tunge

Beilstein J. Org. Chem. 2012, 8, 1200–1207, doi:10.3762/bjoc.8.133

• the biologically active coumarin motif. This new method was utilized to prepare a 128-membered library of aminated coumarins for biological screening. Keywords: benzylation; catalysis; coumarin; chemical diversity; decarboxylative; palladium; substitution; Introduction Coumarins are privileged

• nucleophiles [45][46][47][48][49][50][51][52][53][54][55]. In this realm, we [53][55] and others [54] have focused efforts on catalyzing benzylic substitutions with less-stabilized (DMSO pKa ~ 20–30) nucleophiles through decarboxylative coupling. In the present context, we hypothesized that a broad diversity

• hydroxymethylcoumarins, we chose to investigate their decarboxylative couplings of enolates. We have previously shown that decarboxylative benzylation (DcB) is a useful method for the addition of less-stabilized enolate anions to a benzyl functionality [46][53][54][55]. Thus, we envisioned being able to add various

Phytoalexins of the Pyrinae: Biphenyls and dibenzofurans

• Cornelia Chizzali and
• Ludger Beerhues

Beilstein J. Org. Chem. 2012, 8, 613–620, doi:10.3762/bjoc.8.68

• intermediate, which undergoes intramolecular C2→C7 aldol condensation and decarboxylative elimination of the terminal carboxyl group to give 3,5-dihydroxybiphenyl (Figure 4). BIS activity was first detected in cell cultures of S. aucuparia treated with yeast extract as an elicitor [22]. A BIS cDNA was cloned

Aldol elaboration of 4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridin-4-ones, masked precursors to acylpyridones

• Raymond C. F. Jones,
• Abdul K. Choudhury,
• James N. Iley,
• Mark E. Light,
• Georgia Loizou and
• Terence A. Pillainayagam

Beilstein J. Org. Chem. 2012, 8, 308–312, doi:10.3762/bjoc.8.33

• four steps by the route shown in Scheme 3, involving palladium-catalysed decarboxylative ring opening of cyclic carbonates [23]. Thus the enolate of α-tetralone was added to propenal in an aldol addition (LDA, THF, −78 °C; 86%). The second step involved the reduction of the intermediate β-hydroxyketone

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• inexpensive and easily available phenol derivatives (Scheme 23) [71]. More user-friendly sulfamates also proved to be convenient arylating agents in Pd(0)-catalyzed direct substitutive arylation of various oxazole series (Scheme 24) [72]. The first remarkable examples of catalytic, decarboxylative direct

• decarboxylative direct C–H cross-coupling sequence with the residual ester group (Scheme 25a) [73]. Mechanistically, a Cu(II)-catalyzed decarboxylation reaction produces the C4-cuprated azole, which intercepts the arylpalladium acetate complex produced by prior palladation of the substrate at the C2-position, to

• -free, Pd(II)-based catalyst for direct decarboxylative cross-coupling of azole with various benzoic acids (Scheme 26a). In particular, benzoxazole was successfully coupled with 2,6-dimethoxybenzoic acid in 45% yield. Thus, without the assistance of a strong base, a carbopalladation was proposed as a

Highly efficient gold(I)-catalyzed Overman rearrangement in water

• Dong Xing and
• Dan Yang

Beilstein J. Org. Chem. 2011, 7, 781–785, doi:10.3762/bjoc.7.88

• moderate yields were achieved [25][26][27][28]. Very recently, our group developed an efficient gold(I)-catalyzed decarboxylative aza-Claisen rearrangement of allylic N-tosylcarbamates for the synthesis of N-tosyl allylic amines [29]. This reaction was performed in water and therefore represented an

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

• and co-workers introduced another version of the Heck reaction in 2002, in which they converted mostly electron-rich aromatic carboxylic acids and alkenes to vinyl arenes with the release of CO2 [21][22][23]. This decarboxylative Heck reaction allows the direct conversion of benzoic acids without

• prior activation, but requires the addition of stoichiometric amounts of both base and an oxidant. In the original protocol, an excess of silver carbonate (3 equiv) was added to fulfil these functions. The work of Myers represents a milestone in the development of palladium-catalyzed decarboxylative