The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Phenylsilane as an effective desulfinylation reagent

• Wanda H. Midura,
• Aneta Rzewnicka and
• Jerzy A. Krysiak

Beilstein J. Org. Chem. 2017, 13, 1513–1517, doi:10.3762/bjoc.13.150

• ). Oxidation of the crude mixture by stirring with chromium trioxide and pyridine allowed to obtain desulfinylated ketone 13 in a reasonable yield. For acyclic structures the reaction course dramatically depended on the character of ketone. In the case of aliphatic ketone 15, silane treatment gave

Sulfamide chemistry applied to the functionalization of self-assembled monolayers on gold surfaces

• Loïc Pantaine,
• Vincent Humblot,
• Vincent Coeffard and
• Anne Vallée

Beilstein J. Org. Chem. 2017, 13, 648–658, doi:10.3762/bjoc.13.64

• aminothiophenol (4-ATP, Fluka Inc. ≥95%) was prepared at 0.001 M in absolute ethanol. The gold surfaces are constituted of glass substrates (11 mm × 11 mm), successively coated with a 50 Å thick layer of chromium and a 200 nm thick layer of gold, were purchased from Arrandee (Werther, Germany). The gold-coated

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

• 2-hydroxy-1-indanones 111a–c (Scheme 35) [60]. The chromium η6-1,2-dioxobenzocyclobutene complex 112 could be converted into 1-indanones 113 and 114 by addition of vinyllithium derivatives, followed by a double anionic oxy-Cope rearrangement under mild conditions (Scheme 36) [61]. The derivative 114

(Z)-Selective Takai olefination of salicylaldehydes

• Stephen M. Geddis,
• Caroline E. Hagerman,
• Warren R. J. D. Galloway,
• Hannah F. Sore,
• Jonathan M. Goodman and
• David R. Spring

Beilstein J. Org. Chem. 2017, 13, 323–328, doi:10.3762/bjoc.13.35

• ; Introduction The Takai olefination (or Takai reaction) is a method for the conversion of aldehydes 1 into the corresponding alkenyl halides 2 using a haloform–chromium(II) chloride (CHX3–CrCl2) system (Scheme 1A) [1][2]. It is believed that the haloform is first converted to a nucleophilic gem-dichromium

• )-stereoselectivity observed in the chromium(II)-mediated homologation of aldehydes to alkenes (including vinyl halides). The salient features of both models are the same (Scheme 2). It is presumed that the addition of the gem-dichromium species 3 to the aldehyde 1 proceeds via a six-membered pseudo-chair transition

• state 5 containing two chromium ions bridged by a halogen. The less sterically hindered equatorial positions are occupied by the aldehyde substituent (R1 in Scheme 2) of 1 and halide group (X) of 3 and the aldehyde oxygen is thought to be coordinated to one of the Cr centres (the “coordinating” Cr

Chromium(II)-catalyzed enantioselective arylation of ketones

• Gang Wang,
• Shutao Sun,
• Ying Mao,
• Zhiyu Xie and
• Lei Liu

Beilstein J. Org. Chem. 2016, 12, 2771–2775, doi:10.3762/bjoc.12.275

• /bjoc.12.275 Abstract The chromium-catalyzed enantioselective addition of carbo halides to carbonyl compounds is an important transformation in organic synthesis. However, the corresponding catalytic enantioselective arylation of ketones has not been reported to date. Herein, we report the first Cr

• ; asymmetric catalysis; chromium; ketone; tertiary alcohol; Introduction Catalytic enantioselective carbon–carbon bond formation reactions have achieved enormous development during the last few decades as a consequence of the growing demand for enantiopure compounds in modern industry, especially the

• pharmaceutical industry. The chromium (Cr)-catalyzed enantioselective addition of carbo halides to carbonyl compounds is one of the most reliable methods in organic chemistry for chemoselective and structurally diverse synthesis [1][2][3][4][5][6][7][8][9]. To date, the Cr-catalyzed enantioselective carbonyl

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

• Michael Nonnenmacher,
• Dominik M. Buck and
• Doris Kunz

Beilstein J. Org. Chem. 2016, 12, 1884–1896, doi:10.3762/bjoc.12.178

• carbodicarbenes [50][51], in which the carbon atom has a formal oxidation state of ±0 (Figure 1) [52][53][54]. Earlier, we had prepared their tungsten and chromium carbonyl complexes, but could not find deviations of the CO stretching frequencies from those of analogous NHC complexes [55]. As this might be due to

Cross-linked cyclodextrin-based material for treatment of metals and organic substances present in industrial discharge waters

• Élise Euvrard,
• Nadia Morin-Crini,
• Coline Druart,
• Justine Bugnet,
• Bernard Martel,
• Cesare Cosentino,
• Virginie Moutarlier and
• Grégorio Crini

Beilstein J. Org. Chem. 2016, 12, 1826–1838, doi:10.3762/bjoc.12.172

• their own treatment plants, generally physicochemical decontamination steps, the DWs still contain non-negligible amounts of pollutants. Among them, metals (in particular chromium, nickel and zinc) are commonly found at concentrations in the range of milligrams per liter, and organic molecules, such as

• given in the Experimental section. In addition, it was observed that without Ca2+ cations the removal efficiency was above 99%, except for aluminum and chromium (Table 1). When expressing these results in mmol of total metal retained per gram of polymer, it can be noted that for the highest

Molecular weight control in organochromium olefin polymerization catalysis by hemilabile ligand–metal interactions

• Stefan Mark,
• Hubert Wadepohl and
• Markus Enders

Beilstein J. Org. Chem. 2016, 12, 1372–1379, doi:10.3762/bjoc.12.131

• polymerization. All complexes investigated show very high catalytic activity and the additional side arm minimizes chain-transfer reactions, leading to increase of molecular weights of the resulting polymers. Keywords: chromium single-site catalysts; olefin polymerization; ultra-high molecular weight

• role in olefin polymerization [18][19][20][21][22][23][24]. Cyclopentadienyl (Cp)-based chromium complexes exhibit very good ethylene polymerization properties, when the coordination sphere of the chromium center is completed by an additional ligand. Improved stability and hence polymer productivities

• side arm [53][54]. We have recently described how external modifiers combined with Cp-chromium polymerization catalysts influence the chain-termination process and hence the molecular weight of the produced polyethylene [55]. This paper describes our results with covalently linked modifiers and their

Reactivity studies of pincer bis-protic N-heterocyclic carbene complexes of platinum and palladium under basic conditions

• David C. Marelius,
• Curtis E. Moore,
• Arnold L. Rheingold and
• Douglas B. Grotjahn

Beilstein J. Org. Chem. 2016, 12, 1334–1339, doi:10.3762/bjoc.12.126

• even longer. In 1968, Wanzlick and Öfele separately synthesized mercury(II) and chromium(0) imidazol-2-ylidene complexes [3]. Nearly 50 years of NHC ligand research have demonstrated the importance of the electronic and steric effects that can be modified by altering the alkyl or aryl groups on each

On the mechanism of imine elimination from Fischer tungsten carbene complexes

• Philipp Veit,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125

• chromium (by py or CO) for Cr(CO)5(E/Z-4) and Cr(CO)5(Z-6). Both pathways are compatible with the formation of the metal-containing products fac-[Cr(CO)3(py)3] and Cr(CO)6 by dissociation of the imines E-5 or E-7 or by dissociation of the carbenes E-4 or E-6, respectively (Scheme 1b,c) [42][44]. The

• ΔG‡ = 108 kJ mol−1. This barrier is significantly higher than that reported for (methoxy)(methyl)carbene(pentacarbonyl)chromium(0) Cr(CO)5(C(OMe)Me) (52 kJ mol−1 (experimental) and ca. 61 kJ mol−1 (theoretical)) due to the larger steric bulk of the (aminoferrocenyl)ferrocenylcarbene 2, the higher π

• aminocarbenes, experiments on the synthesis and decomposition of carbene(tetracarbonyl)(phosphane) complexes of chromium and tungsten revealed the exclusive formation of cis-M(CO)4(PR3)(carbene) (R = n-Bu, Ph) [83][84][85]. M(CO)5(PR3) and trans-M(CO)4(PR3)2 (M = Cr, W) have been detected as side-products [83

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

• [14][15]. An alternative method [16] involves the photooxygenation of cyclohepta-1,3,5-triene with singlet oxygen in carbon tetrachloride solution, methanolysis of the formed isomeric endoperoxides resulted in 1,2-dihydro-3-hydroxytropone and oxidation of the latter with chromium trioxide. A

Robust bifunctional aluminium–salen catalysts for the preparation of cyclic carbonates from carbon dioxide and epoxides

• Yuri A. Rulev,
• Zalina Gugkaeva,
• Victor I. Maleev,
• Michael North and
• Yuri N. Belokon

Beilstein J. Org. Chem. 2015, 11, 1614–1623, doi:10.3762/bjoc.11.176

• developed for the production of cyclic carbonates [7][8][9] and polycarbonates [10][11] from carbon dioxide and epoxides, the most developed and privileged set of catalysts are based on Lewis acidic metal–salen complexes. In particular, cobalt(III) and chromium(III) complexes were found to be highly

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• metals (such as chromium and manganese) [20][21][22]. Many SCPC oxidations of aromatics have been reported, but of these it is perhaps the oxidation of benzene to phenol that is the most industrially significant [23][24]. Unfortunately, product selectivity is poor because the phenol itself undergoes

Surprisingly facile CO₂ insertion into cobalt alkoxide bonds: A theoretical investigation

• Willem K. Offermans,
• Claudia Bizzarri,
• Walter Leitner and
• Thomas E. Müller

Beilstein J. Org. Chem. 2015, 11, 1340–1351, doi:10.3762/bjoc.11.144

• carbonates. In consequence, industrially relevant catalysts, combined with efficient processes, have only recently emerged for the manufacture of alternating polycarbonates [10] and polyethercarbonates [11]. The respective research has mainly focussed on homogeneous zinc–alkoxide complexes [12] and chromium

• explored in several studies. Rieger et al. studied the mechanisms of the copolymerisation by homogeneous chromium(III)– and aluminium(III)–salen complexes and by heterogeneous zinc-dicarboxylates [30][31]. Experimental work on the chromium(III)– and aluminium(III)–salen complexes was combined with a

• 1.96 Å to 2.12 Å) as well as the CO2 molecule is bent (OCO angle 146.7°). The new C–O and Cr–O bonds (after CO2 insertion) form synchronously, without prior activation by binding to the Lewis acidic Cr(III) center, as the coordination sphere of chromium is saturated. Regarding Al(III)–salen complexes

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

• benzannulation of a biscarbene complex 319 with 1,9-decadiyne (271) delivered [6,6]metacyclophane 318 (31%) (Scheme 55). Dötz and Gerhardt [191] have synthesized the [2,2]metacyclophane via chromium-mediated intermolecular benzannulation. In this connection, methoxy(alkynyl)carbene complex undergo an

An integrated photocatalytic/enzymatic system for the reduction of CO₂ to methanol in bioglycerol–water

• Michele Aresta,
• Angela Dibenedetto,
• Tomasz Baran,
• Antonella Angelini,
• Przemysław Łabuz and
• Wojciech Macyk

Beilstein J. Org. Chem. 2014, 10, 2556–2565, doi:10.3762/bjoc.10.267

• rutin (rutin@TiO2) shows an electron injection into the conduction band of TiO2 as the result of a direct molecule-to-band charge transfer (MBCT) within the surface-formed, colored, charge-transfer complex of titanium(IV) [21]. TiO2 with an adsorbed chromium(III) anionic complex [CrF5(H2O)]2– acts as a

• generates a photocurrent upon visible light irradiation, proving a photoinduced electron transfer from the excited chromium(III) complex to the conduction band of TiO2 (Figure 6). The following step, that is, the transfer of electrons from the conduction band of the photocatalyst to the oxidized form of the

• the chemical stability and photostability of photocatalysts, are also under continuous investigation for their further improvement and bring the whole reaction closer to a potential application. Conclusion Titanium dioxide modified with chromium(III) complex, [CrF5(H2O)]2−@TiO2, exhibits great ability

Copolymerization and terpolymerization of carbon dioxide/propylene oxide/phthalic anhydride using a (salen)Co(III) complex tethering four quaternary ammonium salts

• Jong Yeob Jeon,
• Seong Chan Eo,
• Jobi Kodiyan Varghese and
• Bun Yeoul Lee

Beilstein J. Org. Chem. 2014, 10, 1787–1795, doi:10.3762/bjoc.10.187

• using a diiminate zinc catalyst as well as a chromium(III) salen complex have been reported [26][27]. Long reaction times (>10 h) were needed to reach full conversion, and the average molecular weights were in the region of several ten thousand. When a zinc glutarate catalyst was used in PO/PA

Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

• Ludovic Eberlin,
• Fabien Tripoteau,
• François Carreaux,
• Andrew Whiting and
• Bertrand Carboni

Beilstein J. Org. Chem. 2014, 10, 237–250, doi:10.3762/bjoc.10.19

• , the catalytic asymmetric version was carried out efficiently in the presence of the Jacobsen’s tridentate chromium(III) complex 20 catalyst with high diastereo- and enantioselectivity (Scheme 17). The first application of this strategy in the synthesis of natural products and analogues concerned (5R

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

• product was obtained after oxidation of the tetrahydrofuran to the desired natural product salvileucalin B (292) using chromium trioxide·3,5-dimethylpyrazole [218]. Oxygen variants overview The divinyloxirane rearrangement (293 to 294, see Scheme 36) has been investigated in detail by the groups of White

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

• chromium(VI) oxide yielded the aldehyde 1.67 required for the previously described Knoevenagel condensation. The five membered heterocycle 2,4-thiazolidinedione (1.68) is readily available commercially, but can be easily prepared at scale via a simple cyclocondensation between thiourea and chloroacetic

Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

• Verena Weidmann,
• Mathias Schaffrath,
• Holger Zorn,
• Julia Rehbein and
• Wolfgang Maison

Beilstein J. Org. Chem. 2013, 9, 2233–2241, doi:10.3762/bjoc.9.262

• ] or α,β-unsaturated carbonyl compounds are attractive synthetic targets of high economic and scientific interest [11][12][13][14][15][16][17]. Allylic oxidations of olefins to enones have classically been performed with strong oxidants such as chromium or other metal-based reagents [18][19]. In

Hypervalent iodine/TEMPO-mediated oxidation in flow systems: a fast and efficient protocol for alcohol oxidation

• Nida Ambreen,
• Ravi Kumar and
• Thomas Wirth

Beilstein J. Org. Chem. 2013, 9, 1437–1442, doi:10.3762/bjoc.9.162

• ; Introduction Oxidation of alcohols to carbonyl compounds plays an important role in organic chemistry. The transformation is traditionally achieved by using chromium-based reagents such as the Collins reagent, activated manganese dioxide, or procedures known as the Swern [1], Pfitzner–Moffatt [2] or Parikh

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

• further examples of iron(II) SCO compounds have been published [7][8][9][10][11][12][13][16][17][18][19][20][21][22][23][24][25][26][27][28], and other coordination compounds of 3d transition elements such as cobalt(II) [29][30], and to a much lesser extent cobalt(III), chromium(II), manganese(II

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• catalytic carbomagnesiation of dialkylacetylenes. Note that Ilies and Nakamura reported iron-catalyzed annulation reactions of various alkynes, including dialkylacetylenes with 2-biphenylylmagnesium reagents to form phenanthrene structures [113]. In 2007, Yorimitsu and Oshima reported that chromium chloride

• reagents (Scheme 54) [147]. They assumed that the active species were organocuprates and that the radical character of carbocupration enabled bulky sec- or tert-alkylmagnesium reagents to be employed. Chromium-catalyzed carbomagnesiation of 1,6-diyne (Scheme 55) [148] and 1,6-enyne (Scheme 56) [149] also

• provided interesting organomagnesium intermediates through cyclization reactions [150]. Treatment of 1,6-diyne 5j with methallylmagnesium reagent in the presence of chromium(III) chloride afforded bicyclic product 5k in excellent yield. In the proposed mechanism, the chromium salt was firstly converted to