Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins

• Christiane Schultze and
• Bernd Schmidt

Beilstein J. Org. Chem. 2018, 14, 2991–2998, doi:10.3762/bjoc.14.278

• catalyze allylic and benzylic oxidation reactions through a radical mechanism [70]. To implement this tandem sequence in the synthesis of pyran-2-one-annellated coumarins 15 an isomerization of the 8-allyl substituent to a prop-1-enyl substituent was first required. When 8-allyl-7-hydroxycoumarin (8a) was

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• initial dream that AMMs can be used one day to perform different tasks on the molecular level becomes slowly but steadily true. TTF and its derivatives will continue to contribute to this process. The two one-electron oxidation reactions of tetrathiafulvalene (TTF, 1) and the corresponding property

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• the reaction is not dependent on the catalytic cycle characterisation – either reductive or oxidative quenching. Net oxidative reactions require the presence of an oxidising agent. The advantage of photoredox net oxidative reactions, compared to conventional oxidation reactions, is that much milder

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• reactions involving a step that enables the introduction of the iodoarene side-compound into the products. Various sequences combining oxidation reactions, nucleophilic additions, or aromatic couplings, thus, have been reported (Scheme 1b). In addition to address the issue of sustainability, this

• using Oxone as a terminal oxidant, thereby allowing for extending the scope of the reaction in terms of iodoarenes. Tandem oxidation–catalytic couplings A large range of oxidation reactions can be performed with [bis(acyloxy)iodo]arenes best represented by the commercially available reagents PhI(OAc)2

Spectroelectrochemical studies on the effect of cations in the alkaline glycerol oxidation reaction over carbon nanotube-supported Pd nanoparticles

• Dennis Hiltrop,
• Steffen Cychy,
• Karina Elumeeva,
• Wolfgang Schuhmann and
• Martin Muhler

Beilstein J. Org. Chem. 2018, 14, 1428–1435, doi:10.3762/bjoc.14.120

• /C, PdAg/C [23] and PtBi/C [21] in alkaline medium using IR spectroscopy for product identification. Strmcnik et al. [24] investigated the effect of different alkali ions using LiOH, NaOH, KOH and CsOH on the observed currents in the hydrogen oxidation, oxygen reduction and methanol oxidation

• reactions over Pt single crystal, polycrystalline Pt and Pt/C electrodes. They proposed two different adsorbate structures of hydrated alkali metal cations on the electrode, either via a hydrogen bonding between hydrating water and two OHad groups (1) or direct ion–dipole interactions between two OHad and

• influence on the water electrolysis on Pt(111) [28] and Ir(111)/oxide electrodes [29]. Different Pt single crystal surfaces [30] and other electrochemical reactions such as CO [30], formate [31] and ethylene glycol oxidation [32][33] were studied as well. Especially for these more complex oxidation

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Hypervalent iodine-guided electrophilic substitution: para-selective substitution across aryl iodonium compounds with benzyl groups

• Cyrus Mowdawalla,
• Faiz Ahmed,
• Tian Li,
• Kiet Pham,
• Loma Dave,
• Grace Kim and
• I. F. Dempsey Hyatt

Beilstein J. Org. Chem. 2018, 14, 1039–1045, doi:10.3762/bjoc.14.91

• that many of these useful reagents became a staple in synthetic chemistry laboratories [1][2]. Although hypervalent iodine reagents are commonly used in oxidation reactions, they have also found their own niche in useful C–C bond-formation and C–H activation reactions [3][4][5]. One such C–C bond

2-Iodo-N-isopropyl-5-methoxybenzamide as a highly reactive and environmentally benign catalyst for alcohol oxidation

• Takayuki Yakura,
• Tomoya Fujiwara,
• Akihiro Yamada and
• Hisanori Nambu

Beilstein J. Org. Chem. 2018, 14, 971–978, doi:10.3762/bjoc.14.82

• isophthalic acids (SIBX) [39] has been reported. Nevertheless, from a green chemistry viewpoint, pentavalent iodine oxidants are not ideal because oxidation reactions require a stoichiometric amount of the oxidant that produces an equimolar amount of organoiodine waste. The catalytic use of pentavalent iodine

• room temperature, appears to be a promising catalyst for efficient and environmentally benign alcohol oxidation reactions [67]. Herein, we report our efforts on improving the reactivity of 2-iodobenzamide catalysts. Results and Discussion We evaluated several 2-iodobenzoic acid derivatives including

• and 38% trivalent 28. Thus, it is clear that the pentavalent iodine species 2 and 29 were generated during the oxidation reactions of monovalent 3 and 17 and that the oxidation of trivalent 27 to pentavalent 29 is much faster than that of 28 to 2 at room temperature. These results also suggest that

Biocatalytic synthesis of the Green Note trans-2-hexenal in a continuous-flow microreactor

• Morten M. C. H. van Schie,
• Tiago Pedroso de Almeida,
• Gabriele Laudadio,
• Florian Tieves,
• Elena Fernández-Fueyo,
• Timothy Noël,
• Isabel W. C. E. Arends and
• Frank Hollmann

Beilstein J. Org. Chem. 2018, 14, 697–703, doi:10.3762/bjoc.14.58

• described in the literature to alleviate the inactivation issue described above [9][10][11][12]. The continuous-flow microreactor technology has emerged as a safe and scalable way to approach oxidation reactions [13][14]. Due to its small dimensions, hazardous reactions can be easily controlled, owing to

• high O2-transfer rates thereby enabling efficient and robust oxidase-catalysed oxidation reactions. Results and Discussion Selection and characterisation of the biocatalyst As biocatalyst for this study we focussed on the recombinant aryl alcohol oxidase from Pleurotus eryngii (PeAAOx) [28][29][30][31

Oxidative cycloaddition of hydroxamic acids with dienes or guaiacols mediated by iodine(III) reagents

• Hisato Shimizu,
• Akira Yoshimura,
• Keiichi Noguchi,
• Victor N. Nemykin,
• Viktor V. Zhdankin and
• Akio Saito

Beilstein J. Org. Chem. 2018, 14, 531–536, doi:10.3762/bjoc.14.39

• complicated [2][3][4][5]. Although the Swern–Moffat oxidation [6], Dess–Martin oxidation [7], and metal-mediated/catalyzed oxidation reactions [8][9][10][11][12] are known as alternative methods [13][14], these methods suffer from a narrow scope and/or low product yields. Furthermore, in the cases where these

Quinone-catalyzed oxidative deformylation: synthesis of imines from amino alcohols

• Xinyun Liu,
• Johnny H. Phan,
• Benjamin J. Haugeberg,
• Shrikant S. Londhe and
• Michael D. Clift

Beilstein J. Org. Chem. 2017, 13, 2895–2901, doi:10.3762/bjoc.13.282

• deformylation of 2-phenylglycinol (1a) to deliver N-PMP imine 7a (Table 1). We selected quinone catalysts (2a−c) that have previously been utilized in amine oxidation reactions [21][32][40][41], and began with reaction conditions similar to those developed for our quinone-catalyzed oxidative decarboxylation

Homologated amino acids with three vicinal fluorines positioned along the backbone: development of a stereoselective synthesis

• Raju Cheerlavancha,
• Ahmed Ahmed,
• Yun Cheuk Leung,
• Aggie Lawer,
• Qing-Quan Liu,
• Marina Cagnes,
• Hee-Chan Jang,
• Xiang-Guo Hu and
• Luke Hunter

Beilstein J. Org. Chem. 2017, 13, 2316–2325, doi:10.3762/bjoc.13.228

• . However, the p-nitro group of 40a,b now posed a complication, because aryl oxidation reactions are only facile for electron-rich systems [39][40]. Unsurprisingly, when the oxidation reaction was attempted under standard NaIO4/RuCl3 conditions [39][40] with the nitroaryl substrate 40a, no reaction was

Mechanically induced oxidation of alcohols to aldehydes and ketones in ambient air: Revisiting TEMPO-assisted oxidations

• Andrea Porcheddu,
• Evelina Colacino,
• Giancarlo Cravotto,
• Francesco Delogu and
• Lidia De Luca

Beilstein J. Org. Chem. 2017, 13, 2049–2055, doi:10.3762/bjoc.13.202

• reaction exhibited higher yields and rates than the classical, homogeneous, TEMPO-based oxidation. Keywords: aldehydes; ball milling; ketones; mechanochemistry; oxidation reactions; TEMPO; Introduction Aldehydes and ketones constitute some of the most powerful and versatile building blocks that are

• choice of solvent for TEMPO-based oxidative procedures remains a crucial issue in the development of greener alternatives to traditional alcohol oxidation reactions [32][33][34]. In particular, the lack of a green option significantly decreases the attractiveness of the proposed synthetic routes, as the

New bio-nanocomposites based on iron oxides and polysaccharides applied to oxidation and alkylation reactions

• Daily Rodríguez-Padrón,
• Alina M. Balu,
• Antonio A. Romero and
• Rafael Luque

Beilstein J. Org. Chem. 2017, 13, 1982–1993, doi:10.3762/bjoc.13.194

• both oxidation and acid catalyzed processes. Among all the known oxidative transformations, the oxidation of alcohols to ketones and aldehydes have gained a lot of attention for the research community due to its broad range of industrial applications [38][39]. Nonetheless, the scale up of the oxidation

• reactions has been very restricted due to the use of heavy metals, the limited selectivity for highly functionalized compounds, and the thermal hazards posed [40]. Consequently, catalytic reactions should be further investigated in order to find new alternatives to conventional oxidation methods that

• , for 5 and 10 min, respectively. The microwave-assisted alkylation of toluene and oxidation of benzyl alcohol was carried out in a CEM-Discover microwave reactor, equipped with a PC-controlled interface. The alkylation reactions were carried out by the standard "open vessel" method, while for oxidation

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• common organic solvents except DMSO and also its explosive nature at higher temperature [188]. They could overcome these limitations by using IBX under solvent-free mechanomilling conditions. They have demonstrated various oxidation reactions, synthesis of benzimidazoles, deprotection of dithianes, etc

Experimental and theoretical investigations into the stability of cyclic aminals

• Edgar Sawatzky,
• Antonios Drakopoulos,
• Martin Rölz,
• Christoph Sotriffer,
• Bernd Engels and
• Michael Decker

Beilstein J. Org. Chem. 2016, 12, 2280–2292, doi:10.3762/bjoc.12.221

• with aldehydes or ketones yielding bicyclic structures [25][26][27], or by the reduction of the corresponding dihydroquinazolinones [15][16][17] (Scheme 1). The aminal templates obtained can be used as starting materials for the synthesis of a broad spectrum of diverse structures. Oxidation reactions

• ] (Scheme 2). Furthermore, copper-catalysed reactions or oxidation with sodium hypochlorite were also described to yield the aromatic quinazoline core [26][29][30] (Scheme 2). Besides all the oxidation reactions described, also reductive conditions applying NaBH4 onto the tetrahydroquinazoline-based aminal

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• to alkyl-containing ketones to give the target products in yields of 30–91% and good regioselectivity 7:1 to 20:1 (Scheme 28) [261]. Asymmetric oxidation: Asymmetric Baeyer–Villiger oxidation reactions can be performed using chiral acetals, organic hydroperoxides, chiral metal complexes and

Biosynthesis of α-pyrones

• Till F. Schäberle

Beilstein J. Org. Chem. 2016, 12, 571–588, doi:10.3762/bjoc.12.56

• , for most of them the clarification of the biosynthesis remained unknown for many years. An early example for a biosynthetic hypothesis is the biosynthesis of the simple 6-pentyl-α-pyrone (29), which was hypothesized to start with the C-18 linoleic acid. This acid is then shortened by β-oxidation

• reactions to a C-10 intermediate, i.e., 5-hydroxy-2,4-decenoic acid (72), which undergoes lactonization to yield 29 (Figure 17) [34]. This hypothesis is based on the fact that feeding studies with Trichoderma harzianum and T. viride using [U-14C]linoleic acid or [5-14C]sodium mevalonate revealed the

Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

• David Porter,
• Belinda M.-L. Poon and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 2549–2556, doi:10.3762/bjoc.11.275

• reaction volume of 1 mL). Under these conditions the yield of allylic amine 9 doubled relative to the more dilute 1:1 reaction, to 17%; 10 and 11 were not observed. Reaction using a chiral catalyst The chiral catalyst Fe(R,R′)-PDP (6) has been used previously to promote asymmetric C–H oxidation reactions

Active site diversification of P450cam with indole generates catalysts for benzylic oxidation reactions

• Paul P. Kelly,
• Anja Eichler,
• Susanne Herter,
• David C. Kranz,
• Nicholas J. Turner and
• Sabine L. Flitsch

Beilstein J. Org. Chem. 2015, 11, 1713–1720, doi:10.3762/bjoc.11.186

Chiroptical properties of 1,3-diphenylallene-anchored tetrathiafulvalene and its polymer synthesis

• Masashi Hasegawa,
• Junta Endo,
• Seiya Iwata,
• Toshiaki Shimasaki and
• Yasuhiro Mazaki

Beilstein J. Org. Chem. 2015, 11, 972–979, doi:10.3762/bjoc.11.109

• cationic species of TTF in any cationic species derived from 3 or PTDPA. Only small changes of λfirst and λsecond peaks, mainly associated with the 1,3-diphenylallene framework, were observed during the oxidation reactions. In the present chiral system, the chiroptical effects between two TTF units are

Hetero-Diels–Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles

• Grzegorz Mlostoń,
• Paulina Grzelak,
• Maciej Mikina,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2015, 11, 576–582, doi:10.3762/bjoc.11.63

• the present study were used for oxidation reactions aimed at the preparation of the corresponding sulfoxides and sulfones. As demonstrated in a recent publication [20], polycyclic sulfones are attractive substrates for the synthesis of polycyclic hydrocarbons via thermal SO2 extrusion. In our

• ). The course of the oxidation reactions for these thiopyrans differs from a similar process reported for Se-containing systems. In these cases, ring contraction and elimination of an aryl group, but no formation of an oxidized product, was observed [21]. The same report describes the appearance of

Electrochemical oxidation of cholesterol

• Jacek W. Morzycki and
• Andrzej Sobkowiak

Beilstein J. Org. Chem. 2015, 11, 392–402, doi:10.3762/bjoc.11.45

• toxic products. These are formed due to oxidation reactions caused by the contact with oxygen, the exposure to sunlight, heating treatments, etc. [5][6][7]. Furthermore, they can be generated in the human organism through different oxidation processes, some of which require enzymes. Cholesterol

A simple and efficient method for the preparation of 5-hydroxy-3-acyltetramic acids

• Johanna Trenner and
• Evgeny V. Prusov

Beilstein J. Org. Chem. 2015, 11, 323–327, doi:10.3762/bjoc.11.37

• the reaction was essentially complete in 20 minutes according to TLC analysis. Oxidation reactions performed in polar aprotic solvents, such as DMPU and DMF, gave significantly lower yields compared to THF. As with the parent tetramic acids, isolation and purification of the hydroxylated derivatives

Photovoltaic-driven organic electrosynthesis and efforts toward more sustainable oxidation reactions

• Bichlien H. Nguyen,
• Robert J. Perkins,
• Jake A. Smith and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2015, 11, 280–287, doi:10.3762/bjoc.11.32

• conducting a wide variety of sustainable oxidation reactions. The approach presented in this article is compatible with both direct and indirect oxidation reactions, avoids the need for a stoichiometric oxidant, and leads to hydrogen gas as the only byproduct from the corresponding reduction reaction

• . Keywords: electrochemistry; sustainable oxidation reactions; visible light; Introduction Organic electrochemistry is an extremely versatile tool for conducting a wide variety of chemical reactions [1][2][3]. This versatility stems from both the gentle, acid/base neutral reaction conditions employed for

• cathode. For all of the oxidation reactions highlighted in this work, this reduction reaction leads to the formation of hydrogen gas. In addition to the direct oxidation of a substrate described in the preceding paragraph, indirect electrochemical methods also offer a powerful means of recycling chemical