Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes

• M. Emin Cinar,
• Bernward Engelen,
• Martin Panthöfer,
• Hans-Jörg Deiseroth,
• Jens Schlirf and
• Michael Schmittel

Beilstein J. Org. Chem. 2016, 12, 813–824, doi:10.3762/bjoc.12.80

• ][10][11], stereoselective syntheses [12][13][14][15][16], and tandem reactions [17][18][19]. While the latter processes usually comprise only one aldol reaction, tandem reaction sequences containing two consecutive aldol steps are mostly limited to the trimerization of enolates [20][21][22]. Metal

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• nitronate, which reacts with the electrophilic nitroolefin via a Michael addition. The resulting nitro compound is again deprotonated by the organocatalyst and reacts with the α,β-unsaturated ester to yield the desired product. Cascade/domino/tandem reactions producing six-membered rings Cascade and tandem

• reactions always seemed very appealing to the synthetic community, not only because of their elegance, but also for their efficiency [36][37][38][39][40][41][42]. Cascade and tandem reactions have been proven extremely efficient because in only one synthetic operation, many bond-forming steps are achieved

• . Organocatalysis has made many contributions in cascade and tandem processes [43][44][45], due to the mild conditions required for the organocatalysts to operate, many distinct reactions can be conducted in one-pot fashion. Cascade/domino/tandem reactions producing six-membered rings initiated by Michael addition

Enabling technologies and green processes in cyclodextrin chemistry

• Giancarlo Cravotto,
• Marina Caporaso,
• Laszlo Jicsinszky and
• Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

• preliminary study on sonochemical Staudinger-aza-Wittig tandem reactions [20] proving that isocyanate and urea formation is strongly favored. However, the applied power must be optimised for the best conversions of azido-CD into urea to be obtained and if lower efficiency in the second step is to be avoided

Facile synthesis of 4H-chromene derivatives via base-mediated annulation of ortho-hydroxychalcones and 2-bromoallyl sulfones

• Srinivas Thadkapally,
• Athira C. Kunjachan and
• Rajeev S. Menon

Beilstein J. Org. Chem. 2016, 12, 16–21, doi:10.3762/bjoc.12.3

• ], multicomponent reactions [8], ring-closing metathesis approaches [9][10], tandem reactions of 1,3-dicarbonyl compounds [11][12] and cyclocondenzation reactions of salicylic aldehydes with α,β-unsaturated carbonyl compounds [13][14][15]. The utility of some of these methods are limited by drawbacks such as

Cross metathesis of unsaturated epoxides for the synthesis of polyfunctional building blocks

• Meriem K. Abderrezak,
• Kristýna Šichová,
• Nancy Dominguez-Boblett,
• Antoine Dupé,
• Zahia Kabouche,
• Christian Bruneau and
• Cédric Fischmeister

Beilstein J. Org. Chem. 2015, 11, 1876–1880, doi:10.3762/bjoc.11.201

• cross metathesis of 1 with methyl acrylate was transformed by means of nucleophilic ring-opening of the epoxide to furnish a diol, an alkoxy alcohol and an amino alcohol in high yields. Keywords: cross metathesis; epoxide; ruthenium catalysts; tandem reactions; Introduction Catalytic carbon–carbon

Tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds

• Javier Miró,
• María Sánchez-Roselló,
• Álvaro Sanz,
• Fernando Rabasa,
• Carlos del Pozo and
• Santos Fustero

Beilstein J. Org. Chem. 2015, 11, 1486–1493, doi:10.3762/bjoc.11.161

• tandem CEYM–IMDAR protocol. The results of these tandem reactions are depicted in Table 3. Diolefinic substrate 8a underwent the tandem sequence in excellent yield (85%) to afford the endo isomer 10a-endo as the major product together with a small amount of the exo isomer 10a-exo (Table 3, entry 1). On

Properties of PTFE tape as a semipermeable membrane in fluorous reactions

• Brendon A. Parsons,
• Olivia Lin Smith,
• Myeong Chae and
• Veljko Dragojlovic

Beilstein J. Org. Chem. 2015, 11, 980–993, doi:10.3762/bjoc.11.110

• limitations due to the densities of the reagents or substrates and they can be used in sequential or tandem reactions, or reactions under reflux [21][22][23]. We also utilized alternative PTFE-covered vials to simplify reagent handling [24]. The PV-PTFE method can be made more efficient by better

Synthesis of 2-trifluoromethylpyrazolo[5,1-a]isoquinolines via silver triflate-catalyzed or electrophile-mediated one-pot tandem reaction

• Xiaoli Zhou,
• Meiling Liu,
• Puying Luo,
• Yingjun Lai,
• Tangtao Yang and
• Qiuping Ding

Beilstein J. Org. Chem. 2014, 10, 2286–2292, doi:10.3762/bjoc.10.238

• interest in developing an efficient method for the synthesis of fluorinated heterocycles. Perfluoroalkynoate is a versatile and powerful building block for generating functionalized perfluoroalkylated compounds, especially fluorinated heterocycles, by tandem reactions [19][20][21][22][23][24][25][26]. For

• . ORTEP diagrams of 3b and 4h. Screening of conditions for the silver triflate-catalyzed reaction of N’-(2-alkynylbenzylidene)hydrazide 1a with ethyl 4,4,4-trifluorobut-2-ynoate 2a. Silver triflate-catalyzed tandem reactions of N’-(2-alkynylbenzylidene)hydrazides 1 with ethyl 4,4,4-trifluorobut-2-ynoate 2

• . One-pot tandem reactions of N’-(2-alkynylbenzylidene)hydrazides 1, electrophiles, and ethyl 4,4,4-trifluorobut-2-ynoate (2)a. Supporting Information Supporting Information File 532: Characterization data and NMR spectra. Supporting Information File 533: X-ray data for compound 3b. Supporting

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• F2, 3-butynoates underwent [3 + 2] annulations with electron-deficient olefins, providing highly functionalized cyclopentenes in 66–95% yield with 81–99% ee (Scheme 36) [70]. Interestingly, this acyclic catalyst proved to be remarkably efficient at mediating these tandem reactions, despite its

• organocatalytic asymmetric domino reactions allow the rapid construction of structurally complex molecules from readily available starting materials in two or more steps in a single operation, they have attracted much attention. Bifunctional chiral phosphines are ideal chiral catalysts for tandem reactions. In

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• -coupling products into tandem reactions. The second goal could be achieved by classifying reactions on the basis of the involved reactants, the reaction type or the role of the catalyst. Review A3-coupling-type reactions Silver catalysis The catalytic direct 1,2-addition of alkynes to imines and iminium

Aminofluorination of 2-alkynylanilines: a Au-catalyzed entry to fluorinated indoles

• Antonio Arcadi,
• Emanuela Pietropaolo,
• Antonello Alvino and
• Véronique Michelet

Beilstein J. Org. Chem. 2014, 10, 449–458, doi:10.3762/bjoc.10.42

• ; indoles; tandem reactions; Introduction Introducing fluorine atoms into organic molecules still faces challenges in organic synthesis [1]. Organofluorine compounds found growing use in various areas including pharmaceuticals, agrochemicals, and materials [2]. A significant proportion of pharmaceuticals

Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

• Ludovic Eberlin,
• Fabien Tripoteau,
• François Carreaux,
• Andrew Whiting and
• Bertrand Carboni

Beilstein J. Org. Chem. 2014, 10, 237–250, doi:10.3762/bjoc.10.19

• studies on the synthesis of 2-boron-substituted 1,3-dienes and their reactivity in tandem reactions, concentrating mainly upon [4 + 2]-cycloadditions followed by cross-coupling reactions. Potassium and tetra-n-butylammonium buta-1,3-dienyl-2-trifluoroborates 15 were synthesized in good yields from

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• condition. Final reduction gave core skeleton 233. DVCPR in tandem reactions The group of Stoltz [196][197] succeeded in establishing a tandem Wolff rearrangement/divinylcyclopropane rearrangement strategy [198]. Readily accessible α-diazo ketone 234 (see Scheme 28) was shown to undergo Wolff rearrangement

• - and gold-catalyzed versions of tandem reactions involving a DVCPR. Tungsten, platinum and gold catalysed cycloisomerizations leading to a DVCPR. Reisman’s total synthesis of salvileucalin B, featuring an (undesired) vinylcyclopropyl carbaldehyde rearrangement. Studies on the divinylepoxide

Silica: An efficient catalyst for one-pot regioselective synthesis of dithioethers

• Samir Kundu,
• Babli Roy and
• Basudeb Basu

Beilstein J. Org. Chem. 2014, 10, 26–33, doi:10.3762/bjoc.10.5

• Samir Kundu Babli Roy Basudeb Basu Department of Chemistry, North Bengal University, Darjeeling 734013, India, Fax: +91 353 2699001 10.3762/bjoc.10.5 Abstract The development of a silica-promoted highly selective synthesis of 1,2 or 1,3-dithioethers via solvent-free one-pot tandem reactions of an

• ; silica gel; tandem reactions; thiol; Introduction Organosulfur compounds are important building blocks for the synthesis of various biologically active molecules [1][2][3]. Versatile applications of organosulfur compounds are known in fields such as the pharmaceutical, the polymer, the pesticide and the

• relatively low yields (Table 1, entries 9 and 10). Interestingly, allylphenylsulfane or allyl phenyl ether entirely followed an anti-Markovnikov addition, under both conditions, A and B (Table 1, entries 11–14). With the two distinct conditions, we examined the scope of these one-pot tandem reactions of

Post-Ugi gold-catalyzed diastereoselective domino cyclization for the synthesis of diversely substituted spiroindolines

• Amit Kumar,
• Dipak D. Vachhani,
• Sachin G. Modha,
• Sunil K. Sharma,
• Virinder S. Parmar and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2013, 9, 2097–2102, doi:10.3762/bjoc.9.246

• ) involves short reaction sequences, a strong focus on bond construction, and functional group compatibility [1][2][3]. Reactions that involve multiple bond formation, such as multicomponent reactions [4][5][6][7][8][9] and tandem reactions [10][11][12][13][14][15][16], are very useful in this context. As an

Gold-catalyzed intermolecular coupling of sulfonylacetylene with allyl ethers: [3,3]- and [1,3]-rearrangements

• Jungho Jun,
• Hyu-Suk Yeom,
• Jun-Hyun An and
• Seunghoon Shin

Beilstein J. Org. Chem. 2013, 9, 1724–1729, doi:10.3762/bjoc.9.198

• organic chemistry, mediating a variety of C–C and C–X (heteroatom) bond formations, various tandem reactions and rearrangements [1]. Despite these significant advances, overcoming entropic penalty in intermolecular coupling of alkenes with alkynes is still a major challenge in gold catalysis, reflected by

Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions

• Matthias Leven,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2013, 9, 155–165, doi:10.3762/bjoc.9.18

• famous examples are Mac Millan’s secondary-amine-based catalysts [6] or 9-amino-9-deoxy-epihydroquinine salts used by Jørgensen et al. [7][8]. Another growing field of catalysis is metal-promoted organocatalysis, which is closely related to tandem reactions of metal- and organocatalysis [9][10][11][12

Reactions of salicylaldehyde and enolates or their equivalents: versatile synthetic routes to chromane derivatives

• Ishmael B. Masesane and
• Zelalem Yibralign Desta

Beilstein J. Org. Chem. 2012, 8, 2166–2175, doi:10.3762/bjoc.8.244

• -amine-mediated tandem reactions of salicylaldehyde and α,β-unsaturated compounds to give chromane derivatives have been reported. Stukan and co-workers, for example, used an Et3N-mediated reaction of salicylaldehyde (5) and nitropropene 46 in the synthesis of 2,3-disubstituted chromene 47 in a low yield

Parallel and four-step synthesis of natural-product-inspired scaffolds through modular assembly and divergent cyclization

• Hiroki Oguri,
• Haruki Mizoguchi,
• Hideaki Oikawa,
• Aki Ishiyama,
• Masato Iwatsuki,
• Kazuhiko Otoguro and
• Satoshi Ōmura

Beilstein J. Org. Chem. 2012, 8, 930–940, doi:10.3762/bjoc.8.105

• module 3, we then synthesized precursors 45 and 46 with a terminal alkyne and a furan ring, respectively, by using amine building blocks 43 and 44 according to the reported procedure [22]. The Rh(II)-catalyzed tandem reactions of 45 and 46 again proceeded at module 3 to produce cyclized products 47 and

• . The modular assembly of 15 with 16, 17 and 8 based on Ugi condensation could produce a different dipeptidyl array of the precursor 18, which is expected to produce the distinct scaffold 19 compared to those produced from manifold 6. According to this strategy employing rhodium(II)-catalyzed tandem

• reactions, four sp2-centers were efficiently converted into the corresponding sp3-centers, including an aminoacetal core. In nature, there are a variety of alkaloids that possess an aminoacetal group (Figure 2b). The aminoacetal groups embedded in the skeleton are prone to undergo C–O bond cleavage to form

Two-directional synthesis as a tool for diversity-oriented synthesis: Synthesis of alkaloid scaffolds

• Kieron M. G. O’Connell,
• Monica Díaz-Gavilán,
• Warren R. J. D. Galloway and
• David R. Spring

Beilstein J. Org. Chem. 2012, 8, 850–860, doi:10.3762/bjoc.8.95

• technology for DOS. The initial DOS campaign was largely inspired by the pioneering work of Robert Stockman on combining two-directional synthesis with tandem reactions to create complex molecular architectures [15][16][17][18]. The key folding step in the DOS was the Lewis acid mediated pairing reaction of

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• strategies to form these bonds in more convenient ways. In this review, we highlight recent advances in the gold-catalyzed chemistry of addition of X–H (X = O, N, C) bonds to C–C multiple bonds, tandem reactions, and asymmetric additions. This review covers gold-catalyzed organic reactions published from

• ]. Furthermore, the rapid growing area of tandem reactions has allowed chemists to assemble diverse complex molecular frameworks more conveniently. Although various research efforts have led to gold-catalyzed addition reactions, the area of asymmetric addition has only recently been pioneered. Currently, a broad

• that cover several aspects of gold-catalyzed additions to unsaturated bonds: (i) X–H (X = O, N, C) bonds to C–C multiple bonds; (ii) tandem reactions; and (iii) gold-catalyzed asymmetric additions. The literature published from 2008 up to the February of 2011 is covered. Only the most important recent

Gold-catalyzed propargylic substitutions: Scope and synthetic developments

• Olivier Debleds,
• Eric Gayon,
• Emmanuel Vrancken and
• Jean-Marc Campagne

Beilstein J. Org. Chem. 2011, 7, 866–877, doi:10.3762/bjoc.7.99

• substitution reactions. BF3 vs AuCl3 in propargylic substitutions [25]. The use of bis-nucleophiles in direct propargylic substitutions. Tandem reactions from protected hydroxylamines and propargylic alcohols. P = Cbz, PhSO2. Tentative hydrolysis of bis-adduct 24a. Iron-catalyzed propargylic substitutions

Solvent- and ligand-induced switch of selectivity in gold(I)-catalyzed tandem reactions of 3-propargylindoles

• Estela Álvarez,
• Delia Miguel,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez,
• Félix Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2011, 7, 786–793, doi:10.3762/bjoc.7.89

• , temperature), in the gold(I)-catalyzed tandem reactions of 3-propargylindoles initiated by 1,2-indole migrations. We have been able to switch the preference of 3-propargylindoles, bearing (hetero)aromatic substituents at both propargylic and terminal positions of the alkyne moiety, from undergoing an aura-iso

Synthesis of fluorinated δ-lactams via cycloisomerization of gem-difluoropropargyl amides

• Satoru Arimitsu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2010, 6, No. 48, doi:10.3762/bjoc.6.48

• reaction time. The stereochemistry of 7a and 7b was determined by COSY and NOESY experiments. Recently, various tandem reactions with ruthenium complexes have become popular in organic chemistry because Ru(II) complexes are capable of catalyzing additional reactions [26][27]. Since our enyne metathesis

• (Scheme 3). In summary, gem-difluoro-1,7-enyne carbonyl derivatives are useful reaction partners in enyne metathesis cycloisomerization and CM–EYM tandem reactions catalyzed by ruthenium carbene complexes. The resulting diene products can be elaborated further using a Diels–Alder reaction. Comparison of

Prins fluorination cyclisations: Preparation of 4-fluoro-pyran and -piperidine heterocycles

• Guillaume G. Launay,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2010, 6, No. 41, doi:10.3762/bjoc.6.41

• in the products, differing only in the orientation of the fluorine. In general, these reactions gave good diastereoselectivities in moderate to good yields (Scheme 3). Aza-Prins fluorination reaction The aza-Prins reaction is less well known but has been exploited, e.g., in tandem reactions in