Diaminoterephthalate–α-lipoic acid conjugates with fluorinated residues

• Leon Buschbeck,
• Aleksandra Markovic,
• Gunther Wittstock and
• Jens Christoffers

Beilstein J. Org. Chem. 2019, 15, 981–991, doi:10.3762/bjoc.15.96

• cleaned glass slides as the support by depositing 0.5 nm of chromium by electron-beam evaporation as adhesion layer and 200 nm of gold by resistive heating using an evaporation chamber (minicoater, Tectra GmbH, Frankfurt, Germany). The thickness was monitored by means of a quartz crystal microbalance

Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes

• Yo Hiranoi and
• Koji Nakano

Beilstein J. Org. Chem. 2018, 14, 2779–2788, doi:10.3762/bjoc.14.255

• -workers reported that the dinuclear chromium–salan complex showed a much higher catalytic activity than the corresponding mononuclear chromium–salan complex in the copolymerization of epoxides with maleic anhydride (MA) [31]. Following this report, some dinuclear metal complexes have been reported to

Anomeric modification of carbohydrates using the Mitsunobu reaction

• Julia Hain,
• Patrick Rollin,
• Werner Klaffke and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138

• outcome of the reaction towards β-configured products [53]. In this case, phenolic chromium tricarbonyl complexes of weaker acids such as p-cresol were employed to improve the yield. The challenge of glycoside synthesis using sugars devoid of a C-2 participating group is also highlighted by a total

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

• Kimihiro Komeyama Shunsuke Sakiyama Kento Iwashita Itaru Osaka Ken Takaki Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Higashi-Hiroshima City 739-8527, Japan 10.3762/bjoc.14.118 Abstract The cobalt/chromium-catalyzed three-component coupling of aryl

• , whereas the chromium salt generates highly nucleophilic allylchromium intermediates from allylcobalt species, without the loss of stereochemical information, to allow the addition to aldehydes. Keywords: chromium; cobalt; diastereoselective; homoallyl alcohols; hybrid catalyst; three-component coupling

• organometallics, involving a wide range of transition metal-catalyzed reactions. For example, transmetalation between an organonickel (or organocobalt) complex and chromium salt results in the formation of a highly nucleophilic organochromium species, which enables efficient addition to aldehydes to give

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

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

• fundamental and frequently used transformation in organic synthesis. Heavy metal-based oxidants such as chromium(VI), lead(IV), and mercury(II) have been extensively used for this purpose for a long time. However, these oxidants are highly toxic and produce hazardous waste. Recently, hypervalent iodine

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• under ball-milling conditions, Lamaty and co-workers showed that deterioration of vessels and balls by physical abrasion and/or chemical leaching gave products in which (depending upon the nature of the jar) iron, chromium, zirconia or PTFE were detected [20]. This has influenced the choice of vessel

Latest development in the synthesis of ursodeoxycholic acid (UDCA): a critical review

• Fabio Tonin and
• Isabel W. C. E. Arends

Beilstein J. Org. Chem. 2018, 14, 470–483, doi:10.3762/bjoc.14.33

• aspects. Conclusion The organic synthesis of CDCA and UDCA starting from taurinated and glycinated cholic acid is a long process, complicated and risky due to the nature and toxicity of the reagents used, the costs of disposal of large amounts of sodium hydroxide, chromium salts and organic solvents, and

Recent developments in the asymmetric Reformatsky-type reaction

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 325–344, doi:10.3762/bjoc.14.21

• previously reported syntheses by the fact that it included for the first time as key step a totally diastereoselective chromium-mediated macrolactonization. The same year, Schulze et al. reported the synthesis of chiral β-hydroxy-α-methyl-δ-trichloromethyl-δ-valerolactone (39) through a diastereoselective Sm

Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres

• Myriam Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262

• bond isostere [6]. Using this strategy, a mutant tripeptide containing two different peptide bond isosteres could be synthesized (Figure 3). In 2016, Konno and co-workers developed a stereoselective chromium-mediated C–F bond cleavage followed by a C–C bond formation to access (Z)-monofluoroalkenes

• with excellent selectivity (Scheme 4) [28]. The chromium-mediated coupling of 1-bromo-4-(tert-butyldiphenylsiloxy)-1,1-difluorobutane (15) with aldehyde 16 led to the formation of monofluoroalkene 17. This was then reacted with sodium azide and a further Staudinger reduction gave 18. Boc protection of

• co-workers. Synthesis of Phth-Gly-ψ[CF=CH]-Gly using the Julia–Kocienski olefination by Lequeux and co-workers. Synthesis of Boc-Nva-ψ[(Z)-CF=CH]-Gly by Taguchi and co-workers. Chromium-mediated synthesis of Boc-Ser(PMB)-ψ[(Z)-CF=CH]-Gly-OMe by Konno and co-workers. Synthesis of Cbz-Gly-ψ[(E)-CF=C

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