Glycoluril–tetrathiafulvalene molecular clips: on the influence of electronic and spatial properties for binding neutral accepting guests

• Yoann Cotelle,
• Marie Hardouin-Lerouge,
• Stéphanie Legoupy,
• Olivier Alévêque,
• Eric Levillain and
• Piétrick Hudhomme

Beilstein J. Org. Chem. 2015, 11, 1023–1036, doi:10.3762/bjoc.11.115

• onto compound 11 [34]. The hydroquinone moieties were subjected to a dehydrogenation reaction using DDQ in THF to reach desired glycolurildiquinone 13 [35] in 91% yield. The Diels–Alder cycloaddition was carried out by treatment of bis-dienophile 13 with TTF derivative 14 [36], able to give rise in

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• radical mechanisms were proposed, the common feature is the generation of alkene via the radical dehydrogenation of alkane. 2.6 Other oxidative systems Esters were synthesized from aldehydes and methanol (6 equiv excess relative to aldehyde) using pyridinium dichromate in DMF [170]. Methyl esters were

• afforded molecular hydrogen and unsymmetrical ester 187 (Scheme 39) [182]. Cross-coupling products 187 were obtained in high yields; the expected homocoupling of primary alcohols giving symmetrical esters and the dehydrogenation of secondary alcohols yielding ketones were avoided. 3 Ketones and 1,3

Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids

• Roman Matthessen,
• Jan Fransaer,
• Koen Binnemans and
• Dirk E. De Vos

Beilstein J. Org. Chem. 2014, 10, 2484–2500, doi:10.3762/bjoc.10.260

• for the polymer industry. 1,3-Butadiene is widely available, not only from steam cracking, but increasingly from dehydrogenation of linear butenes. Dicarboxylation of 1,3-butadiene yields a mixture of 3-hexene-1,6-dioic acid isomers, which are only one hydrogenation step removed from adipic acid, a

New highlights of the syntheses of pyrrolo[1,2-a]quinoxalin-4-ones

• Emilian Georgescu,
• Alina Nicolescu,
• Florentina Georgescu,
• Florina Teodorescu,
• Daniela Marinescu,
• Ana-Maria Macsim and
• Calin Deleanu

Beilstein J. Org. Chem. 2014, 10, 2377–2387, doi:10.3762/bjoc.10.248

• imidazole ring-opening, initiated by the deprotonation at C-1 of the primary cycloadducts 8, followed by ring-closure involving the carbethoxy C=O group, a previously proposed rationale [9]. The formation of pyrrolo[1,2-a]benzimidazoles 5 involves the spontaneous in situ dehydrogenation of the primary

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

• treated under various oxidation conditions (including DDQ, IBX, SeO2, and MnO2) to install the tropone moiety by dehydrogenation, but unfortunately all these reaction conditions failed. Compound 22 was subsequently converted into the free acid 23 by treatment with TFA, while similar conversions of 20 and

Domino reactions of 2H-azirines with acylketenes from furan-2,3-diones: Competition between the formation of ortho-fused and bridged heterocyclic systems

• Alexander F. Khlebnikov,
• Mikhail S. Novikov,
• Viktoriia V. Pakalnis,
• Roman O. Iakovenko and
• Dmitry S. Yufit

Beilstein J. Org. Chem. 2014, 10, 784–793, doi:10.3762/bjoc.10.74

• the reaction involving dihydropyrazines 11 on the way to 4 and 5 could be quite competitive with the reaction leading to 3, provided that a source of dihydropyrazines 11 is available. Formation of ‘dimer azirines’, dihydropyrazines [37][38][39][40][41], or products of their dehydrogenation, pyrazines

An oxidative amidation and heterocyclization approach for the synthesis of β-carbolines and dihydroeudistomin Y

• Suresh Babu Meruva,
• Akula Raghunadh,
• Raghavendra Rao Kamaraju,
• U. K. Syam Kumar and
• P. K. Dubey

Beilstein J. Org. Chem. 2014, 10, 471–480, doi:10.3762/bjoc.10.45

• dehydrogenation with DBU in different solvents at various temperatures also failed and did not yield the required product. Attempted oxidation of compound 7 under microwave irradiation conditions was also not successful. Probably under all aforementioned conditions, formation of the stable enol 21 might have

• retarded the aromatization during the course of dehydrogenation reaction of dihydro-β-carboline 7. Utilizing the oxidative amidation Bischler–Napieralski reaction conditions we have synthesized a number of dihydro-β-carbolines (Table 2) in moderate to good yields. The structures of these compounds were

Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones

• Murat Kucukdisli,
• Dorota Ferenc,
• Marcel Heinz,
• Christine Wiebe and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 466–470, doi:10.3762/bjoc.10.44

• the literature. They can be obtained from enones by Michael addition of nitromethane, partial reduction and dehydrogenation of the resulting pyrroline with selenium or sulfur in moderate yields (3 steps) [40][41]. Alternatively, a Nef reaction of the nitromethane adducts gives masked 1,4-dicarbonyls

• -dicarbonyl [44]. Compared to this elegant strategy, our two-step protocol provides a higher overall yield of compound 7a and uses less expensive reagents. In addition to the thermal elimination of HCN, intermediates 6 can also be aromatized by dehydrogenation. In this case, the nitrile group remains in the

• pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles by means of a cyclocondensation with aminoacetonitrile and a microwave-assisted dehydrocyanation or a dehydrogenation with DDQ. These methods provide a simple an efficient entry into these useful compound classes. Experimental Typical procedure for the

Synthesis of new enantiopure poly(hydroxy)aminooxepanes as building blocks for multivalent carbohydrate mimetics

• Léa Bouché,
• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 213–223, doi:10.3762/bjoc.10.17

• in situ generated formaldehyde (dehydrogenation of methanol) [50][51][52][53] and subsequent aminal formation with aminooxepanes 26 and 27. The aminoalcohol 28 seems not to form the corresponding compounds. We suppose that bicyclic compound 28 is more strained and hence the formation of a third ring

Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C₂-symmetric building block: a strategy for the synthesis of decanolide natural products

• Bernd Schmidt and
• Oliver Kunz

Beilstein J. Org. Chem. 2013, 9, 2544–2555, doi:10.3762/bjoc.9.289

• obtained. Instead, the dehydrogenation product 13 was the predominant product (Table 4, entry 2). Addition of the base Na2CO3 led only to a small improvement (Table 4, entry 3). Ketone formation has previously been described in attempted DKR’s of secondary alcohols when catalyst C was used in combination

Biosynthesis of rare hexoses using microorganisms and related enzymes

• Zijie Li,
• Yahui Gao,
• Hideki Nakanishi,
• Xiaodong Gao and
• Li Cai

Beilstein J. Org. Chem. 2013, 9, 2434–2445, doi:10.3762/bjoc.9.281

• [44]. Alternatively, D-sorbose could be prepared from L-glucitol via C-2 dehydrogenation through microbial conversion within a reasonable period of time (>95% yield and multigram scale, Scheme 4) [45][46]. The starting material L-glucitol could be obtained from the chemical reduction of a

• multi-enzyme system containing DTEase, ribitol dehydrogenase (RDH, EC 1.1.1.56) and formate dehydrogenase (FDH, EC 1.2.1.2) [99]. In this system, NADH is regenerated by an irreversible formate dehydrogenation reaction, promoting the conversion of D-psicose to allitol. As a result, the D-fructose and D

• activity could be induced by L-arabinose [102]. Moreover, supplement of erythritol to the reaction mixture enhanced the conversion to L-sorbitol and one possible reason also lies in NADH regeneration resulting from erythritol dehydrogenation/oxidation. Conclusion The preparation and functional study of

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

• -methylpiperidine (1.21) using zeolites and easily aromatised by catalytic dehydrogenation to 3-picoline in 78% overall yield (Scheme 4) [26]. The overall processing sequence is highly energy-efficient (coupling of the endothermic cyclisation with the exothermic dehydration gives a reasonable energy balance). In

An approach towards azafuranomycin analogs by gold-catalyzed cycloisomerization of allenes: synthesis of (αS,2R)-(2,5-dihydro-1H-pyrrol-2-yl)glycine

• Jörg Erdsack and
• Norbert Krause

Beilstein J. Org. Chem. 2013, 9, 1936–1942, doi:10.3762/bjoc.9.229

• ] (Scheme 4). This protection step was carried out in order to avoid dehydrogenation or chlorination of the secondary amine in the subsequent oxidation steps [64][65]. Acetal cleavage under mild protic conditions furnished the hydroxycarbamate, which underwent two-step oxidation with Dess–Martin periodinane

Simple and rapid hydrogenation of p-nitrophenol with aqueous formic acid in catalytic flow reactors

• Rahat Javaid,
• Shin-ichiro Kawasaki,
• Akira Suzuki and
• Toshishige M. Suzuki

Beilstein J. Org. Chem. 2013, 9, 1156–1163, doi:10.3762/bjoc.9.129

• residence time in the porous PdO reactor at 40 °C. Evolution of carbon dioxide (CO2) was observed during the reaction, although hydrogen (H2) was not found in the gas phase. Dehydrogenation of formic acid did not occur to any practical degree in the absence of p-nitrophenol. Consequently, the nitro group

• was reduced via hydrogen transfer from formic acid to p-nitrophenol and not by hydrogen generated by dehydrogenation of formic acid. Keywords: catalytic tubular reactor; flow chemistry; formic acid; hydrogenation; p-aminophenol; p-nitrophenol; Introduction The flow reaction process enables

• of 92.1% at 30 °C (Figure 5), which corresponds to a 1.7 times excess of the reducing agent to the p-nitrophenol. Further increases of concentration did not improve the reaction outcomes (Figure 5). Transfer hydrogen from formic acid to p-nitrophenol Dehydrogenation of formic acid and its subsequent

Metal–ligand multiple bonds as frustrated Lewis pairs for C–H functionalization

• Matthew T. Whited

Beilstein J. Org. Chem. 2012, 8, 1554–1563, doi:10.3762/bjoc.8.177

• ) alkoxycarbene. The complex could be generated stoichiometrically when norbornene was utilized as a hydrogen acceptor. The reaction was shown to be general for several methyl ethers and tetrahydrofuran, but other ethers were prone to 1,2-dehydrogenation or decarbonylation [88][89] The use of methyl amines as

An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• cyclohexanone, catalyzed by PPA, followed by dehydrogenation over Pd–C has also been reported for the preparation of the unsubstituted α-carboline [48], but no other successful applications of this strategy have appeared in the literature. A more common strategy to α-carbolines closes the pyridine ring onto an

Synthesis of 2,6-disubstituted tetrahydroazulene derivatives

• Zakir Hussain,
• Henning Hopf,
• Khurshid Ayub and
• S. Holger Eichhorn

Beilstein J. Org. Chem. 2012, 8, 693–698, doi:10.3762/bjoc.8.77

• , which was transformed into the 2,6-disubstituted tetrahydroazulene 7 as a viscous oil. It is important to note that tetrahydroazulenes, in contrast to perhydroazulenes, are not very resistant towards dehydrogenation (oxidation) and, when kept at room temperature for a few days, form the corresponding

• with Schlieren-like textures were present but were never recovered or reproduced. In the case of compound 10, the same behavior was observed. As we mentioned earlier, tetrahydroazulenes, in contrast to perhydroazulenes, are not very resistant against dehydrogenation (oxidation), and when kept at room

Aryl nitrile oxide cycloaddition reactions in the presence of pinacol boronic acid ester

• Sarah L. Harding,
• Sebastian M. Marcuccio and
• G. Paul Savage

Beilstein J. Org. Chem. 2012, 8, 606–612, doi:10.3762/bjoc.8.67

• nitrile oxides involves the dehydration of primary nitro compounds [21]. Aryl nitrile oxides are more commonly prepared by chlorination of aldoximes followed by dehydrohalogenation of the resulting hydroximoyl chlorides, or by direct oxidative dehydrogenation of the aldoximes (Scheme 2) [17]. While the

• halogenation–dehydrohalogenation process is most common, several methods involving direct oxidative dehydrogenation of aldoximes have been reported, including the use of lead tetraacetate [22][23], mercury(II) acetate [24], hypervalent iodine [25][26], and manganese(IV) oxide [27]. We were interested in

Volatile organic compounds produced by the phytopathogenic bacterium Xanthomonas campestris pv. vesicatoria 85-10

• Teresa Weise,
• Marco Kai,
• Anja Gummesson,
• Armin Troeger,
• Stephan von Reuß,
• Silvia Piepenborn,
• Francine Kosterka,
• Martin Sklorz,
• Ralf Zimmermann,
• Wittko Francke and
• Birgit Piechulla

Beilstein J. Org. Chem. 2012, 8, 579–596, doi:10.3762/bjoc.8.65

• , III will directly form 34. On the other hand, reduction of III would furnish IV, and subsequent elimination of water would lead to V, the immediate precursor of 11-methyldodec-2Z-enoic acid. However, V may also be formed upon dehydrogenation of 11-methyldodecanoyl-SCoA (VI), which, in turn, may be

Novel fatty acid methyl esters from the actinomycete Micromonospora aurantiaca

• Jeroen S. Dickschat,
• Hilke Bruns and
• Ramona Riclea

Beilstein J. Org. Chem. 2011, 7, 1697–1712, doi:10.3762/bjoc.7.200

• counterparts 50 and 51 by dehydrogenation. A two-carbon elongation of 50 and 51 by means of the fatty acid biosynthetic pathway can generate 55 and 56, while their reduction to the respective alcohols provides 47 and 48. Acetoin (44) was also found as a major compound, together with its derivatives 3

Manganese dioxide mediated one-pot synthesis of methyl 9H-pyrido[3,4-b]indole-1-carboxylate: Concise synthesis of alangiobussinine

• Jessica Baiget,
• Sabin Llona-Minguez,
• Stuart Lang,
• Simon P. MacKay,
• Colin J. Suckling and
• Oliver B. Sutcliffe

Beilstein J. Org. Chem. 2011, 7, 1407–1411, doi:10.3762/bjoc.7.164

• means of either a Pictet–Spengler or a Bischler–Napieralski cyclization followed by an oxidative dehydrogenation process [13][14][15]. Inspired by nature’s example, we wished to design a synthetic route to the β-carboline scaffold, which was biomimetic and could be carried out in a single operation. One

• tetrahydrocarboline 5. In the presence of manganese dioxide intermediate 5 is not isolated, but instead, undergoes a series of dehydrogenation reactions in order to furnish our desired, fully aromatic β-carboline 6 (Scheme 1). This approach to the synthesis of β-carbolines is particularly elegant as the manganese

Synthesis of novel 5-alkyl/aryl/heteroaryl substituted diethyl 3,4-dihydro-2H-pyrrole-4,4-dicarboxylates by aziridine ring expansion of 2-[(aziridin-1-yl)-1-alkyl/aryl/heteroaryl-methylene]malonic acid diethyl esters

• Satish S. More,
• T. Krishna Mohan,
• Y. Sateesh Kumar,
• U. K. Syam Kumar and
• Navin B. Patel

Beilstein J. Org. Chem. 2011, 7, 831–838, doi:10.3762/bjoc.7.95

• quantitative yields, either by reduction with sodium borohydride, or by catalytic hydrogenation using platinum on carbon [33][34]. The pyrrolines can be aromatized either by a two step procedure (i) NBS bromination and (ii) dehydrohalogenation in basic medium [35][36][37], or by dehydrogenation with Pd/C [38

Molecular rearrangements of superelectrophiles

• Douglas A. Klumpp

Beilstein J. Org. Chem. 2011, 7, 346–363, doi:10.3762/bjoc.7.45

• dehydrogenation. For example, 2-decalone (51) (primarily trans) was reacted with HF-SbF5-CCl4 at 0 °C to give products 52 and 53 in 25% and 12% yields, respectively (Scheme 12). The proposed mechanism involves protonation and hydride abstraction to give superelectrophile 54. It is notable that the carbocation

An expedient and new synthesis of pyrrolo[1,2-b]pyridazine derivatives

• Rajeshwar Reddy Sagyam,
• Ravinder Buchikonda,
• Jaya Prakash Pitta,
• Himabindu Vurimidi,
• Pratap Reddy Padi and
• Mahesh Reddy Ghanta

Beilstein J. Org. Chem. 2009, 5, No. 66, doi:10.3762/bjoc.5.66

• condensation reactions, such as the condensation of oxazolo[3,2-b]pyridazinium perchlorates with malononitrile, ethyl cyanoacetate and ethyl malonate in the presence of sodium ethoxide [15]; the condensation of 1,4,7-triketones with hydrazine followed by dehydrogenation [16]; the condensation of cyanoacetic

A stable enol from a 6-substituted benzanthrone and its unexpected behaviour under acidic conditions

• Marc Debeaux,
• Kai Brandhorst,
• Peter G. Jones,
• Henning Hopf,
• Jörg Grunenberg,
• Wolfgang Kowalsky and
• Hans-Hermann Johannes

Beilstein J. Org. Chem. 2009, 5, No. 31, doi:10.3762/bjoc.5.31

• stable enol 4, which is converted by dehydrogenation into the benzanthrone derivative 7. Under acidic conditions 4 isomerises to the spiro compound 11 and the bicyclo[4.3.1]decane derivative 12. Furthermore, the formation of 7 and the hydrogenated compound 13 is observed. A mechanism for the formation of

• monitored by 1H NMR spectroscopy (Figure 1) in CDCl3. This conversion is much slower when the CDCl3 is filtered through an alumina plug before use. The reaction constitutes a formal dehydrogenation of 4 (Scheme 2). As shown in Scheme 2, we propose that the formation of 4 and 7 starts as a 1,4-addition