Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• precursor of the benzene ring (Scheme 87). This methodology has been applied in the synthesis of 1-indanones (Scheme 88 and Scheme 89). In 2012, Hoye et al. have presented the synthesis of 1-indenone 318 via a hexadehydro-Diels–Alder (HDDA) reaction with simultaneous formation of five and six-membered rings

• from the tetrayne 317 (Scheme 88) [119]. In the reaction participates only three triple bonds marked by red lines. This, catalyzed by MnO2 reaction, is fully regioselective. During the cycloaddition after the formation of the five and six-membered rings, one of the tert-butyldimethylsilyl (TBS) group

Continuous N-alkylation reactions of amino alcohols using γ-Al₂O₃ and supercritical CO₂: unexpected formation of cyclic ureas and urethanes by reaction with CO₂

• Emilia S. Streng,
• Darren S. Lee,
• Michael W. George and
• Martyn Poliakoff

Beilstein J. Org. Chem. 2017, 13, 329–337, doi:10.3762/bjoc.13.36

• be expected from the intramolecular closure of 8, consistent with the results observed with bromoalkylamines [48], and suggesting the rate of closure for three-membered rings is slower than that of five- and six-membered rings. We cannot rule out the formation of aziridine as an intermediate in the

Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/syn-dihydroxylation

• Michał Malik and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2016, 12, 2602–2608, doi:10.3762/bjoc.12.255

• (both in 25 and 26). This is in accordance with the general observation, that E-enolates (enolates in six-membered rings are always E) give predominantly the anti-products in aldol reactions (Zimmerman–Traxler model) [52][53][54]. The application of the above-described procedure to cyclohexenone 18 was

β-Amino functionalization of cinnamic Weinreb amides in ionic liquid

• Yi-Ning Wang,
• Guo-Xiang Sun and
• Gang Qi

Beilstein J. Org. Chem. 2016, 12, 2372–2377, doi:10.3762/bjoc.12.231

• much lower fields (e.g., 8.25 ppm vs 6.33 ppm for compounds 6a-B vs 6a-A). The reason for this phenomenon is probably due to hydrogen bonding between the protons of the nitrobenzenesulfonyl amines and the neighboring carbonyl groups, which form stable six-membered rings as shown in Figure 1. In

A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis

• Mariano Goldberg,
• Denis Sartakov,
• Jan W. Bats,
• Michael Bolte and
• Michael W. Göbel

Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176

• of the guanidinium benzoate salt the six membered rings of 10 adopt conformations close to an envelope with the phenyl substituents in pseudo-axial positions. The unprotonated guanidine 10 catalyzes Diels–Alder reactions of anthrones and maleimides (25–30% ee). It also promotes as a strong Brønsted

The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals

• Sonia L. Repetto,
• James F. Costello,
• Craig P. Butts,
• Joseph K. W. Lam and
• Norman M. Ratcliffe

Beilstein J. Org. Chem. 2016, 12, 1467–1475, doi:10.3762/bjoc.12.143

• -diethoxypropane) is several orders of magnitude greater than 1 [18]. Relative reactivity of cyclic orthoesters; five versus six-membered rings As k1 ≈ kobs in the pH range examined here (Scheme 1), factors associated with the relief of cyclic strain cannot be used to account for the difference observed for five

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• six-membered rings and only four articles described the synthesis of three and seven-membered heterocycles. Additionally, the majority of the reported syntheses were devoted to the development of new methodologies including the use of advanced catalytic systems, alternative solvents and microwave

Stereoselective synthesis of tricyclic compounds by intramolecular palladium-catalyzed addition of aryl iodides to carbonyl groups

• Jakub Saadi,
• Christoph Bentz,
• Kai Redies,
• Dieter Lentz,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1236–1242, doi:10.3762/bjoc.12.118

• not allow an unambiguous determination. Considering the result obtained with the cycloheptanone derivative where two diastereomers could be assigned by X-ray crystal structure analyses make the proposed trans-annulation of the five- and six-membered rings fairly likely. The palladium-catalyzed

Separation and identification of indene–C₇₀ bisadduct isomers

• Bolong Zhang,
• Jegadesan Subbiah,
• David J. Jones and
• Wallace W. H. Wong

Beilstein J. Org. Chem. 2016, 12, 903–911, doi:10.3762/bjoc.12.88

• between C70 and two isoindene molecules generated in situ from indene. The symmetry of the ellipsoidal C70 molecule means that there are four different bonds between two six membered rings ([6,6]-bonds) that can participate in the Diel–Alder reaction. These are known as α-, β-, ε- and κ-bonds (Figure 2a

(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

• main tools a synthetic chemist has to perform asymmetric catalysis. In this review the synthesis of six-membered rings, that contain multiple chiral centers, either by a ring closing process or by a functionalization reaction on an already existing six-membered ring, utilizing bifunctional (thio)ureas

• )ureas have been synthesized in order to utilize both hydrogen bonding interactions and enamine formation. In the last 10 years the field has witnessed the development of some new activation modes, such as SOMO catalysis [8] and photoredox organocatalysis [9]. Six-membered rings are found in many natural

• products, pharmaceuticals and agrochemicals, thus, a lot of effort has been put by the synthetic community to provide mild, reliable, robust and operationally simple methods to construct them. Of the vast variety of six-membered rings, those with multiple chiral centers pose the most difficult synthetic

Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

• Cesar Garcias-Morales,
• David Ortegón-Reyna and
• Armando Ariza-Castolo

Beilstein J. Org. Chem. 2015, 11, 1973–1984, doi:10.3762/bjoc.11.213

• .11.213 Abstract This paper reports the synthesis of a series of piperidones 1–8 by the Mannich reaction and analysis of their structures and conformations in solution by NMR and mass spectrometry. The six-membered rings in 2,4,6,8-tetraphenyl-3,7-diazabicyclo[3.3.1]nonan-9-ones, compounds 1 and 2, adopt

• , and C2, respectively. A signal corresponding to the carbonyl carbon is located at 211.66 ppm. Figure 5a shows the conformations of 1, determined by the t-ROESY experiment. In solution, one of the six-membered rings is in the chair conformation, while the second is in the boat conformation to prevent

• Karplus curve [60]. For 4–8, the six-membered rings exhibit the chair–chair conformation, with both of the phenyl rings in equatorial positions. For 1 and 2, the six-membered rings exhibit the chair–boat conformation, because one nitrogen atom is substituted by a methyl group. As a result, LPE repulsion

The preparation of new functionalized [2.2]paracyclophane derivatives with N-containing functional groups

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

Beilstein J. Org. Chem. 2015, 11, 437–445, doi:10.3762/bjoc.11.50

• cyclophane strain include the following. The bridge C–C single bonds are lengthened to 1.58–1.60 Å, the bridge sp3-bond angles are widened to ca. 112°, and the bridgehead angles within the six-membered rings are narrowed to 116–118°. These rings display a flattened boat conformation (deviations of bridgehead

Articulated rods – a novel class of molecular rods based on oligospiroketals (OSK)

• Pablo Wessig,
• Roswitha Merkel and
• Peter Müller

Beilstein J. Org. Chem. 2015, 11, 74–84, doi:10.3762/bjoc.11.11

• based on spirocyclically joined saturated six-membered rings [8]. The key step of the synthesis of these rods is the formation of ketals and we therefore name this class of compounds oligospiroketals (OSKs). Although the backbone of OSK rods contains many oxygen atoms, these atoms are shielded by

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

• bridge angles and narrowed sp2 ring angles at the bridgehead atoms, and boat-shaped six-membered rings with the bridgehead atoms lying out of the plane of the other four atoms (see Table 2 below). The crystal packing involves two classical and three "weak" hydrogen bonds (two involving the

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

• fullerenes [53]. The carbon–carbon bond shared by two six-membered rings (so-called 6:6-bonds: 1.379 Å) are shorter than those shared by a 5-membered ring and a 6-membered ring (5:6-bonds: 1.430 Å). That is, the carbon–carbon bonds of the hexagonal ring in the center of circumtrindene are not the same as

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

• ease of preparation via IMCRs [27][28][29]. First, the β-lactams will be described followed by five-membered rings varying from pyrrolidines to tetrazoles based amide bond isosteres. Examples of the six-membered rings showing peptide like-properties are the piperazines, homoprolines, dihydropyrimidones

Cyclic phosphonium ionic liquids

• Sharon I. Lall-Ramnarine,
• Joshua A. Mukhlall,
• James F. Wishart,
• Robert R. Engel,
• Alicia R. Romeo,
• Masao Gohdo,
• Sharon Ramati,
• Marc Berman and
• Sophia N. Suarez

Beilstein J. Org. Chem. 2014, 10, 271–275, doi:10.3762/bjoc.10.22

• ammonium salt (101 cP vs 75 cP at 25 °C). For the six-membered rings the phosphonium IL C4mPphin NTf2 5b is slightly less viscous than C4mPip NTf2 (butylmethylpiperidinium NTf2), 171 cP vs 183 cP. Interestingly, the cyclic cations do not follow the common trend among the quaternary tetra-n-alkylated

• cations have greater thermal stability than the ammonium ones. One trend observed for both cation types is that the ILs with five-membered rings have greater thermal stability than those with six-membered rings. Further work will be required to determine if the observed TGA behaviors are due to actual

Stereoselectively fluorinated N-heterocycles: a brief survey

• Xiang-Guo Hu and
• Luke Hunter

Beilstein J. Org. Chem. 2013, 9, 2696–2708, doi:10.3762/bjoc.9.306

• increased ridigity was credited with a dramatic improvement in the enantioselectivity. 3.3 Six-membered rings The conformational analysis of six-membered rings is a cornerstone in physical chemistry. Substituted saturated six-membered compounds usually adopt a chair conformation with substituents preferring

• and Snyder were also able to rule out hydrogen bonding as the source of the axial preference, since the N,N-dimethyl analogue 20 exhibited a similar effect. 3.4 Seven-membered rings Seven-membered rings exhibit much more complex conformational behaviour than six-membered rings. Hence, it is perhaps

Garner’s aldehyde as a versatile intermediate in the synthesis of enantiopure natural products

• Mikko Passiniemi and
• Ari M.P. Koskinen

Beilstein J. Org. Chem. 2013, 9, 2641–2659, doi:10.3762/bjoc.9.300

• six-membered rings. Five-membered dihydrofuran rings lead to the synthesis of furanomycin D [35][36], norfuranomycin E [37], and the polyoxin family F [38]. The six-membered tetrahydropyridine G synthesized via this route can be used as an intermediate in the synthesis of iminosugars, e.g., of the

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

• published review on five-membered rings, will form a comprehensive foundation and reference source for individuals interested in medicinal, synthetic and preparative chemistry. Keywords: heterocycles; medicinal chemistry; pharmaceuticals; six-membered rings; synthesis; Introduction The commonality of six

The preparation of several 1,2,3,4,5-functionalized cyclopentane derivatives

• André S. Kelch,
• Peter G. Jones,
• Ina Dix and
• Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 1705–1712, doi:10.3762/bjoc.9.195

• reason is probably the practical consideration that there are more and higher-yielding preparative routes to three-, four- and six-membered rings than to five-membered ones. Looking at possible precursors for 3, it seems reasonable to start with a substrate that contains at least a complete five-membered

A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates

• František Josefík,
• Markéta Svobodová,
• Valerio Bertolasi and
• Petr Šimůnek

Beilstein J. Org. Chem. 2013, 9, 1463–1471, doi:10.3762/bjoc.9.166

• others are given in Supporting Information File 1. Almost all the structures display some disorder. Structures 5d, 5f, 5j and 5l show disorder in the C3–C7,N3 six-membered rings and the C5H2 moieties were refined over two sites. All the BF4− anions exhibit high temperature factors; in 5d and 5l the

α-Bromodiazoacetamides – a new class of diazo compounds for catalyst-free, ambient temperature intramolecular C–H insertion reactions

• Åsmund Kaupang and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2013, 9, 1407–1413, doi:10.3762/bjoc.9.157

• (Table 1, entries 1–3, products 5a–c), whereas among the derivatives bearing 1,4-heterosubstituted six-membered rings as side chains, poorer yields are obtained (Table 1, entries 4–6, products 5d–f). The latter result could possibly be viewed as an expression of the deactivation of the C–H bonds β to the

Selective copper(II) acetate and potassium iodide catalyzed oxidation of aminals to dihydroquinazoline and quinazolinone alkaloids

• Matthew T. Richers,
• Chenfei Zhao and
• Daniel Seidel

Beilstein J. Org. Chem. 2013, 9, 1194–1201, doi:10.3762/bjoc.9.135

• pyrrolidine-containing aminal adopts a bent structure, whereas the piperidine aminal appears relatively strain-free [34]), this finding likely relates to the reduced propensity of six-membered rings to engage in reactions that form exocyclic double bonds. The isolation of azepinoquinazoline 12 in 73% yield

Polymerization of novel methacrylated anthraquinone dyes

• Christian Dollendorf,
• Susanne Katharina Kreth,
• Soo Whan Choi and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 453–459, doi:10.3762/bjoc.9.48

• -products derived from ring-closure reactions were only found when aliphatic amines with two carbon units between the amine and hydroxy functionality were used. In the synthesis of green and blue dyes, aromatic amines that cannot build six-membered rings were utilized. However, the ring-closure can be