Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• ]. Its absorption extends from UV until 450 nm and can thus be activated at 405 nm with a blue light. Eventually, the peripheral carbazoles can be substituted with halogens. This increases the rate of RISC, and red-shifts the absorption spectrum [81]. For example, with a bromo atom on the peripheral

Pd-Catalyzed microwave-assisted synthesis of phosphonated 13α-estrones as potential OATP2B1, 17β-HSD1 and/or STS inhibitors

• Rebeka Jójárt,
• Szabolcs Pécsy,
• György Keglevich,
• Mihály Szécsi,
• Réka Rigó,
• Csilla Özvegy-Laczka,
• Gábor Kecskeméti and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 2838–2845, doi:10.3762/bjoc.14.262

• inhibitory activity of natural estrone derivatives was the introduction of large halogens and phenethynyl or phenethyl functions onto C-2 of estrone. Their most potent compounds displayed nanomolar inhibitory activities. Our related previous work included the synthesis and in vitro 17β-HSD1 determination of

• similar derivatives of the hormonally inactive 13α-estrane core [21][22][23]. We found that 2- and/or 4-substitution with large halogens (Br or I) lead to submicromolar inhibitors irrespective of the position and number of the introduced halogens. In the case of phenethynyl- or phenethyl-13α-estrones

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• -withdrawing substitutions 7 with 4-hydroxycoumarin (34b) at 70 °C within short reaction times. All aromatic aldehydes 7 reacted with 4-hydroxycoumarin (34b) to form bis-coumarins bearing electron-donating groups, electron-withdrawing groups, and halogens 72 in very short reaction times and in high yields. In

Microwave-assisted synthesis of biologically relevant steroidal 17-exo-pyrazol-5'-ones from a norpregnene precursor by a side-chain elongation/heterocyclization sequence

• Gergő Mótyán,
• László Mérai,
• Márton Attila Kiss,
• Zsuzsanna Schelz,
• Izabella Sinka,
• István Zupkó and
• Éva Frank

Beilstein J. Org. Chem. 2018, 14, 2589–2596, doi:10.3762/bjoc.14.236

• on the reaction rates. The ring-closure of 4 with 5d–g containing electron-donating groups (Table 1, entries 1–4) took place within shorter reaction times (5–10 min) compared to phenylhydrazine (5b). On the other hand the presence of electron-withdrawing halogens on the aromatic ring of 5 (Table 1

Three-component coupling of aryl iodides, allenes, and aldehydes catalyzed by a Co/Cr-hybrid catalyst

• Kimihiro Komeyama,
• Shunsuke Sakiyama,
• Kento Iwashita,
• Itaru Osaka and
• Ken Takaki

Beilstein J. Org. Chem. 2018, 14, 1413–1420, doi:10.3762/bjoc.14.118

• resulting in slightly lower yields (4g, 4g’, 4g” and 4h). Next, the generality of the reaction was investigated using aryl iodides (Scheme 7) and allenes (Scheme 8). Although aryl bromides and chlorides did not participate in the coupling, a diverse set of functional groups such as methoxy (4j), halogens

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• particular, various N-Boc-ketimines exhibiting either electron-donating or electron-withdrawing groups at the 5 and 7 positions of the aryl moiety, including halogens such as fluoro, chloro, bromo and iodo groups, reacted smoothly with pentane-2,4-dione (R2 = R3 = Me) affording the products with both very

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• 24 h) and the isolated yields are often close to 90% for the ordinary substituents (alkyls, aryls, halogens) of the sydnone. Somewhat lower yields were obtained in ethyleneglycol [5]. The reaction of the parent 1-phenylsydnone with DMAD and its diethyl analogue has also been performed in

• mechanism. However, the effect of substituent in position 4- of 3-phenylsydnone is ambiguous. While all halogens substantially accelerate the reaction rate (F > Cl > Br > I) other substituents cause up to tenfold deceleration (H > Me > CF3 > CN) regardless of their polar effects [43][44]. Steric factors

Rhodium-catalyzed C–H functionalization of heteroarenes using indoleBX hypervalent iodine reagents

• Erwann Grenet,
• Ashis Das,
• Paola Caramenti and
• Jérôme Waser

Beilstein J. Org. Chem. 2018, 14, 1208–1214, doi:10.3762/bjoc.14.102

• regioselectivity for the C-6 position of bipyridinones and the C-8 position of quinoline N-oxides and tolerated a broad range of functionalities, such as halogens, ethers, or trifluoromethyl groups. Keywords: C–H activation; hypervalent iodine; indoleBX; indoles; pyridinones; rhodium catalysis; Introduction

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-mediated Ritter-type amidation of terminal alkenes: The synthesis of isoxazoline and pyrazoline cores

• Sang Won Park,
• Soong-Hyun Kim,
• Jaeyoung Song,
• Ga Young Park,
• Darong Kim,
• Tae-Gyu Nam and
• Ki Bum Hong

Beilstein J. Org. Chem. 2018, 14, 1028–1033, doi:10.3762/bjoc.14.89

• , diverse halonium sources have been utilized for the synthesis of isoxazolines via halocyclization. Furthermore, transition metal-, visible light, and hypervalent iodine-mediated oxidative cyclization protocols provide isoxazoline backbones bearing diverse substituents such as –SR, -CF3, -OH and halogens

Diels–Alder cycloadditions of N-arylpyrroles via aryne intermediates using diaryliodonium salts

• Huangguan Chen,
• Jianwei Han and
• Limin Wang

Beilstein J. Org. Chem. 2018, 14, 354–363, doi:10.3762/bjoc.14.23

• groups (Table 2, entries 2 and 3). For those bearing electron-withdrawing groups, such as halogens (F, Cl, Br), cyano, nitro, trifluoromethyl, and trifluoromethoxy groups, the corresponding products 3ad–3aj were obtained in good to excellent yields of 67–96% (Table 2, entries 4–10). It was found that the

Conformational preferences of α-fluoroketones may influence their reactivity

• Graham Pattison

Beilstein J. Org. Chem. 2017, 13, 2915–2921, doi:10.3762/bjoc.13.284

• nucleophilic attack (Figure 5). It would be expected that of all the halogens, fluorine’s lone pairs would overlap most strongly with the carbonyl π*-orbital and decrease its bond order. However, particularly in polar solvents like ethanol, it is the cis conformation (0° O=C–C–X dihedral angle) which is

• dihedral angles and that therefore larger dihedral angles are favoured as this minimizes the molecule’s overall dipole moment. However, computational analysis of the angular variation of the dipole moment of each α-haloacetophenone did not show a significant variation between the different halogens (Figure

• lone pairs and the filled C=O π-orbital. The higher polarizability of higher halogens such as chlorine and bromine may be able to reduce this repulsion, however, the tightly held, non-polarizable lone pairs of fluorine are likely to experience this repulsive effect most strongly. The shorter C–F bond

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• reaction was developed with a wide range of terminal and internal alkenes bearing diverse functional groups such as halogens, nitro, sulfonate, sulfamide, carboxylate, amide, ether, carbonyl, and hydroxy that were all well-tolerated (Scheme 22). A mixed solvent system of dichloromethane and water was used

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane

• James R. Vyvyan,
• Courtney A. Engles,
• Scott L. Bray,
• Erik D. Wold,
• Christopher L. Porter and
• Mikhail O. Konev

Beilstein J. Org. Chem. 2017, 13, 2122–2127, doi:10.3762/bjoc.13.209

• in moderate to excellent yields. When multiple halogens were present, high selectivity for reaction at the aryl iodide was observed (Table 1, entries 3–5). Pyridyl iodide 22 also worked well in the cross-coupling (Table 1, entry 8). Having prepared a number of substituted Z-styrenes, we next focused

Influence of the milling parameters on the nucleophilic substitution reaction of activated β-cyclodextrins

• László Jicsinszky,
• Kata Tuza,
• Giancarlo Cravotto,
• Andrea Porcheddu,
• Francesco Delogu and
• Evelina Colacino

Beilstein J. Org. Chem. 2017, 13, 1893–1899, doi:10.3762/bjoc.13.184

• contact between balls. Unlike the reactivity in solution, under mechanochemical conditions the sulfur nucleophile (thiourea, TU) was less effective than the azide ion in the substitution reaction. A similar reversal of reactivity has been already observed for halogens [12][13][28]. The experimental

Sustainable synthesis of 3-substituted phthalides via a catalytic one-pot cascade strategy from 2-formylbenzoic acid with β-keto acids in glycerol

• Lina Jia and
• Fuzhong Han

Beilstein J. Org. Chem. 2017, 13, 1425–1429, doi:10.3762/bjoc.13.139

• 2b–f, both electron-donating and electron-withdrawing groups such as methyl (2b), methoxy (2c), and halogens (2d–f) afforded the products in relatively high reaction yields. The use of meta-aryl substituted β-keto acids provided the products in good yields, whereas β-keto acid 2i, bearing a methyl

Switchable highly regioselective synthesis of 3,4-dihydroquinoxalin-2(1H)ones from o-phenylenediamines and aroylpyruvates

• Juraj Dobiaš,
• Marek Ondruš,
• Gabriela Addová and
• Andrej Boháč

Beilstein J. Org. Chem. 2017, 13, 1350–1360, doi:10.3762/bjoc.13.132

• -donating groups and halogens (EDG or HG) or (b) with electron-withdrawing (EWG) groups (Table 1, Scheme 6). Using the general procedure A without any additives, diamine 11 was always almost quantitatively consumed (90–100%), and for both clusters of substituents on 11, the main regioisomer of 3,4

• shifted H-N(1) and H-C(8), whereby coupling of HC(5 and 8) depends on type of the regioisomer). It was proved that observed regioselectivity of performed cyclocondensations depends on both a/ the different nucleophilicity of amine groups in diamine 11 (with two clusters of substituents: EDGs + halogens

Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds

• M. Fernanda N. N. Carvalho,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2017, 13, 1230–1238, doi:10.3762/bjoc.13.122

• carbocyclic five-membered ring to the 2,3-position of the bicyclic camphor-derived moiety (Scheme 2a) [20]. Reactions of 4a with halogens (e.g., bromine) or acids were even more puzzling. In addition to the annulation, an unprecedented formation of a ketone accompanied by the reduction of sulphur took place

Phosphorus pentasulfide mediated conversion of organic thiocyanates to thiols

• Chandra Kant Maurya,
• Avik Mazumder and
• Pradeep Kumar Gupta

Beilstein J. Org. Chem. 2017, 13, 1184–1188, doi:10.3762/bjoc.13.117

• of electron withdrawing halogens on the phenyl ring diminished the rate of reaction. It was interesting to note that in this reaction, product yields were found to be less susceptible to substituent effects in comparison to the reaction rates. One of the noticeable features of the present method is

Characterization of non-heme iron aliphatic halogenase WelO5* from Hapalosiphon welwitschii IC-52-3: Identification of a minimal protein sequence motif that confers enzymatic chlorination specificity in the biosynthesis of welwitindolelinones

• Qin Zhu and
• Xinyu Liu

Beilstein J. Org. Chem. 2017, 13, 1168–1173, doi:10.3762/bjoc.13.115

• ], analogous oxidative functionalizations with halogens via C–H activations remain challenging that need to be addressed [9][10][11]. Recently, during the systematic investigation of hapalindole-type alkaloid biogenesis [12][13][14][15][16][17][18][19], we discovered a family of Fe/2OG-dependent halogenases

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• established that the C–H moiety can serve as a hydrogen bond donor and form hydrogen bonds with oxygen, nitrogen or halogens of neutral molecules or anions [17]. However, such interactions have been considered negligible in comparison to much stronger A–H···A hydrogen bonds (A = N, O, F). While Glasstone

• to hydrogen bonds The ability of halogens and halogenated organic compounds to form stable complexes with nucleophiles has been known for more than two centuries [59][60][61]. One of the earliest examples of such complexes were the adducts formed by the reaction of iodine and amylose or ammonia

• described by Colin in 1814 [62]. While the stoichiometry of such complexes was not established at the time, Guthrie in 1863 [63] and Norris in 1896 [64] were able to generate complexes formed between molecular halogens (I2, Br2, and Cl2) and ammonia or methylamines and characterized them. Numerous studies

Continuous-flow synthesis of primary amines: Metal-free reduction of aliphatic and aromatic nitro derivatives with trichlorosilane

• Riccardo Porta,
• Alessandra Puglisi,
• Giacomo Colombo,
• Sergio Rossi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2016, 12, 2614–2619, doi:10.3762/bjoc.12.257

• selectively reduced with quantitative conversions in the presence of ketones (Table 2, entry 1), halogens (Table 2, entries 3–5) and esters (Table 2, entry 6). The methodology was also extended to aliphatic nitro compounds (Scheme 3). These substrates are less reactive than aromatic ones and they typically

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• anion metathesis [29]. There are several reviews detailing these synthetic procedures [30][31]. More sustainable methods that avoid the use of noxious and undesirable halogens have also been recently designed [32][33]. An example is the preparation of methyl carbonate onium salts ([Q1nnn][MeOCO2]; Q = N

Synthesis of pyrrolo[2,1-f][1,2,4]triazin-4(3H)-ones: Rearrangement of pyrrolo[1,2-d][1,3,4]oxadiazines and regioselective intramolecular cyclization of 1,2-biscarbamoyl-substituted 1H-pyrroles

• Kkonnip Son and
• Seong Jun Park

Beilstein J. Org. Chem. 2016, 12, 1780–1787, doi:10.3762/bjoc.12.168

• effect of different halogens on the regioselectivity of the cyclization of 10 was investigated (Table 3). In general, the mixture of oxadiazines 11 and triazinones 12 was obtained in 45–98% overall yield. The results show that the regioselectivity is highly dependent on the halogen used. In particular

On the cause of low thermal stability of ethyl halodiazoacetates

• Magnus Mortén,
• Martin Hennum and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2016, 12, 1590–1597, doi:10.3762/bjoc.12.155

• ) was included in the calculations even though the synthesis of this diazo compound has not been reported in the literature. We excluded 2c in our molecular modeling due to the need for a different basis set for iodine compared to the other halogens. We also included diethyl diazomalonate (2e, t1/2

• alkyl diazocompounds despite the presence of an α-electron-withdrawing-ester group (Figure 7). The primary reason for the low stability of halodiazoacetates is the relatively high stability of their corresponding carbenes due to π-donation from the halogens into the carbenes’ vacant p-orbitals. Ethyl