Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides – scope and limitations

• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1170–1177, doi:10.3762/bjoc.12.112

• acetyl group. This type of aldol condensation that generates a new benzene ring from three acetyl groups was successfully applied in our group in other cases delivering compounds whose 2D self-assembly at highly ordered pyrolytic graphite was studied by STM methods [58][59]. However, in the case of

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• is the case for carbene 19, since the alkyl bridge locks its conformation in such a way that prevents an activating alignment, and the oxygen acts as an inductive electron-withdrawing group. The alkene in the cyclopentene of 20 was oxidatively cleaved, and then an aldol condensation gave the

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

• irreversible formation of the aldol condensation product 6ac, which is obtained in 73% yield in presence of AlCl3, on expense of 5a. The X-ray structure of racemic 5a (from ethanol) could not be solved due to the presence of a solid racemate in the orthorhombic space group P212121 (no. 19). Three axial hydroxy

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• ester 75. Finally, an elegant cascade reaction involving an aldol condensation, followed by a hetereo Diels–Alder reaction closed the last three rings and antheliolide A (18) was obtained in 74% yield. In summary, the successful total synthesis of antheliolide A proceeded in 25 linear steps with an

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

• Yury A. Sayapin,
• Inna O. Tupaeva,
• Alexandra A. Kolodina,
• Eugeny A. Gusakov,
• Vitaly N. Komissarov,
• Igor V. Dorogan,
• Nadezhda I. Makarova,
• Anatoly V. Metelitsa,
• Valery V. Tkachev,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

• solution (method B) is similar to that considered previously for the reaction of o-chloranil with 2-methylquinolines [19] which has been studied by means of DFT PBE0/6-311+G** modelling (Scheme 3, Table 1). At the initial stage, the aldol condensation of the methylene-active heterocyclic compounds with o

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• skeleton using RRM with appropriate norbornene systems. The strategy starts with the aldol condensation of aldehyde 160 with ester 161 in the presence of LDA to generate the required building block 162 in 78% yield. Later, the norbornene derivative 162 was subjected to a RRM sequence under the influence of

• : a sequential aldol condensation of dihydrocarvone with norbornene 2-carboxaldehyde followed by a ROM–RCM of the resulting aldol product. The norbornene derivative 164 was subjected to a RRM using the catalyst 1 to produce the ROM product 165 exclusively. The ring-closure of the resulting ROM product

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2015, 11, 1194–1219, doi:10.3762/bjoc.11.134

• small collection of 22 imidazo[1,2-a]pyridines 136 was prepared within four working days. The synthetic route consisted of an aldol condensation between various acetophenones 137 and ethyl glyoxylate (138). This was followed by an HBF4-catalysed cyclocondensation of the resulting Michael acceptor 139

Five-membered ring annelation in [2.2]paracyclophanes by aldol condensation

• Henning Hopf,
• Swaminathan Vijay Narayanan and
• Peter G. Jones

Beilstein J. Org. Chem. 2014, 10, 2021–2026, doi:10.3762/bjoc.10.210

• -38106 Braunschweig, Germany 10.3762/bjoc.10.210 Abstract Under basic conditions 4,5,12,13-tetraacetyl[2.2]paracyclophane (9) cyclizes by a double aldol condensation to provide the two aldols 12 and 15 in a 3:7 ratio. The structures of these compounds were obtained from X-ray structural analysis

• and spectroscopic data. The sequence presented here constitutes the simplest route so far to cyclophanes carrying an annelated five-membered ring. Keywords: aldol condensation; cyclopentadienones; cyclophanes; multibridged cyclophanes; stereochemistry; X-ray analysis; Introduction We have reported

Synthesis and bioactivity of analogues of the marine antibiotic tropodithietic acid

• Patrick Rabe,
• Tim A. Klapschinski,
• Nelson L. Brock,
• Christian A. Citron,
• Paul D’Alvise,
• Lone Gram and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2014, 10, 1796–1801, doi:10.3762/bjoc.10.188

• . Oxidative cleavage of the glycol with NaIO4 resulted in a β-ketoester aldehyde that upon treatment with silica gel underwent an intramolecular aldol condensation to a mixture of 10a and 11a that were separable by column chromatography. Oxidation with DDQ gave tert-butyl tropone-2-carboxylate (12a) that was

Site-selective covalent functionalization at interior carbon atoms and on the rim of circumtrindene, a C₃₆H₁₂ open geodesic polyarene

• Hee Yeon Cho,
• Ronald B. M. Ansems and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2014, 10, 956–968, doi:10.3762/bjoc.10.94

• ]. Cyclotrimerization of 17 to the C3-symmetric trichlorodecacyclene 12 was accomplished by a triple aldol condensation of the chloro ketone 17 [48][49]. Improvements in the procedures reported previously are described in the experimental section in the Supporting Information File 1. In agreement with DFT calculations

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

• , reduction of the remaining double bond and subsequent Krapcho decarboxylation [132] resulted in less functionalized ketone 150. Aldol condensation with furfural followed by O-allylation and Claisen rearrangement furnished enone 151. Standard functional group interconversiones were used to access TIPS

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• ) units. The remaining methyl groups are believed to be installed by S-adenosyl methionine (SAM). An intramolecular Aldol condensation generates the pyrrolinone 62, which reacts via an [4 + 2]-cycloaddition to prochaetoglobosin I (63) [56]. Recently, gene disruption studies of Chaetomium globosum revealed

•  12) using a dimethylformamide acetal-mediated cyclodehydration of 105. The isoindole unit of 105 was prepared from the condensation of 103 and 104. Oxygen–sulfur exchange provided the thiophthalimide 105, which could be converted to magallanesine (97) via an intramolecular aldol condensation in one

• lateral metalation–cyclization sequence. Metalation of 130 with excess n-butyllithium followed by carbonation then yielded piperolactam C (131). In 2008, Heo and coworkers reported the synthesis of several aristolactams employing a one-pot cross-coupling/aldol condensation cascade reaction (Scheme 17) [91

Total synthesis of ochnaflavone

• Monica M. Ndoile and
• Fanie R. van Heerden

Beilstein J. Org. Chem. 2013, 9, 1346–1351, doi:10.3762/bjoc.9.152

• formation of the chalcone by an aldol condensation reaction with a suitably substituted acetophenone. Selective methylation of 2,4,6-trihydroxyacetophenone with methyl iodide yielded 2'-hydroxy-4',6'-dimethoxyacetophenone (5) in moderate yield. The Claisen–Schmidt condensation of 5 with diaryl ether 4 under

Amyloid-β probes: Review of structure–activity and brain-kinetics relationships

• Todd J. Eckroat,
• Abdelrahman S. Mayhoub and
• Sylvie Garneau-Tsodikova

Beilstein J. Org. Chem. 2013, 9, 1012–1044, doi:10.3762/bjoc.9.116

• and [11C]-labeled chalcones 19a and 19b were synthesized using similar methods, and a representative synthesis of 19a is shown (Scheme 2B). Aldol condensation between the appropriate acetophenone 22 and benzaldehyde 23 afforded the chalcone backbone, which was subsequently pegylated to give 24 and

Direct alkenylation of indolin-2-ones by 6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitriles: a novel approach

• Sandeep Kumar,
• Ramendra Pratap,
• Abhinav Kumar,
• Brijesh Kumar,
• Vishnu K. Tandon and
• Vishnu Ji Ram

Beilstein J. Org. Chem. 2013, 9, 809–817, doi:10.3762/bjoc.9.92

• only recently been reported. There are plenty of literature reports available on the construction of 3-alkenylindolin-2-ones [21]. The widely used highly facile protocol for the alkenylation of indolin-2-ones is through aldol condensation [22] of isatin with compounds containing an active methylene

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• for constructing highly functionalized and enantiomerically enriched tetrahydro-6H-benzo[c]chromenes with five stereogenic centers. The reaction involved a domino oxa-Michael–Michael–Michael–aldol condensation of o-hydroxy-β-nitrostyrene 15 and two equivalents of α,β-unsaturated aldehydes in the

• ).The protocol involved a tandem oxa-Michael–Michael reaction of 3-methyl-but-2-enal (22) and (E)-2-(2-nitrovinyl)-benzene-1,4-diol (21) followed by a domino Michael–aldol condensation with aldehyde 24 in the presence of TMS-protected diphenylprolinol Ib/AcOH as catalyst, affording the hexahydro-6H

• -nitrostyrene, as reported by Das and co-workers. Enantioselective synthesis of 2-aryl-3-nitro-2H-chromenes, as reported by Schreiner. (S)-diphenylpyrrolinol silyl ether-promoted cascade thio-Michael–aldol reactions, as reported by Wang. Organocatalytic asymmetric domino Michael–aldol condensation of

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• upon intramolecular aldol condensation [25][26][27]. Subsequently, the aldehyde 15 was reduced to the allylic alcohol 19 with LiAlH4 and converted into the acetate 20 [28]. Hydroboration of 20 using disiamylborane proceeded with high stereoselectivity affording 16 as a single stereoisomer [17][28

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

• CoA as a starter unit, modular and iterative assembly of malonate extender units produces a linear tetraketide intermediate capable of being folded in at least two ways [5]. Intramolecular Claisen condensation and subsequent enolization produce phloracetophenone (path A), while aldol condensation

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

Catalyst-free and solvent-free Michael addition of 1,3-dicarbonyl compounds to nitroalkenes by a grinding method

• Zong-Bo Xie,
• Na Wang,
• Ming-Yu Wu,
• Ting He,
• Zhang-Gao Le and
• Xiao-Qi Yu

Beilstein J. Org. Chem. 2012, 8, 534–538, doi:10.3762/bjoc.8.61

• ], Aldol condensation [18], etc. [1][2][19][20]. The Michael addition is one of the most fundamental and important reactions for the formation of carbon–carbon bonds and carbon–heteroatom bonds in organic synthesis. The conjugate Michael addition of carbon nucleophiles to electron deficient nitroalkenes is

Syntheses and applications of furanyl-functionalised 2,2’:6’,2’’-terpyridines

• Jérôme Husson and
• Michael Knorr

Beilstein J. Org. Chem. 2012, 8, 379–389, doi:10.3762/bjoc.8.41

• [14]. This strategy was also successfully applied to the preparation of some furanyl-substituted terpyridines. The synthetic sequence starts from furanyl aldehydes 1–3 and 2-acetylpyridine (4). The first step is a base-mediated aldol-condensation that yields the α,β unsaturated ketones 5–7. Reacting

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

• MK7 6AA, United Kingdom EPSRC National Crystallography Service, School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom 10.3762/bjoc.8.33 Abstract A core 4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridine-4-one scaffold is elaborated at C-3(Me) by base-mediated aldol

• condensation to give new 3-alkenyl-4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridine-4-ones, which are masked forms related to the acylpyridone natural products. Keywords: aldol reaction; fused-ring systems; heterocycles; isoxazole; metalation; pyridone; Introduction The 3-acyl-4-hydroxypyridin-2-one moiety 1

Coupled chemo(enzymatic) reactions in continuous flow

• Ruslan Yuryev,
• Simon Strompen and
• Andreas Liese

Beilstein J. Org. Chem. 2011, 7, 1449–1467, doi:10.3762/bjoc.7.169

• formate decarboxylase (BFD) catalyzing the (S)-selective aldol condensation of benzaldehyde (33) and acetaldehyde (32) with formation of (S)-2-hydroxy-1-phenyl-propanone (34) (Scheme 11). In the second vessel the intermediate (S)-34 was asymmetrically reduced by recLb-alcohol dehydrogenase (ADH) and the