Visible light-mediated difluoroalkylation of electron-deficient alkenes

• Vyacheslav I. Supranovich,
• Vitalij V. Levin,
• Marina I. Struchkova,
• Jinbo Hu and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2018, 14, 1637–1641, doi:10.3762/bjoc.14.139

• carbene/borane complex and 400 nm light [48]. Results and Discussion Iodide 1a was selected as a model substrate and its reaction with tert-butyl acrylate (2a) was evaluated in the presence of various boron hydrides (Table 1). The reaction was performed in methanol with irradiation by a strip of blue

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

• involve the formation of the copper-carbene species 35, to which the carboxylate of alkynylbenziodoxolone could add to afford the intermediate 36. Final alkynyl transfer would give rise to the products 31 and 33, however, the nature of this alkynylation step remains to be elucidated. In a subsequent study

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• ][30]. Apart from the strong σ-donor ability, the great interest for these ligands relies on the robustness that they confer to the resulting complexes, upon coordination onto both early [31] and late transition metals [32][33]. In this regard, the group of Chi employed carbene-based chelates as

• neutral imine substitutes in an attempt to further improved the stability and the performances of their N···H–C stabilized phosphors (Figure 5) [34][35]. Either when one, compound 10 [34], or two, compound 11 [35], carbene moieties were used, the resulting platinum compounds were basically nonemissive in

• −1 for 11a, and EQE = 11.2%, CE = 40.6 cd A−1 and PE = 25.8 lm W−1 for 11b. In consequence, the use of only one carbene moiety seemed to afford very appealing photophysical features both for display and lighting applications. The beneficial effect of carbene moieties on the photophysical features of

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• -catalysed reaction with diazo compounds 42 (Scheme 22) [56]. This strategy is not only atom economic regarding the applied hypervalent iodine reagent but also with regard to the chosen substrate. The metal carbene species generated from the diazo compounds displays nucleophilic as well as electrophilic

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• the enolate intermediate 111 followed by the generation of a C–C bond via conjugate addition delivered intermediate carbene 113. A 1,2-hydrogen shift led to the formation of products 108 with enantioselectivities up to 79% (Scheme 24). Later, Maruoka et al. improved the enantioselectivity up to 95% ee

• 115 and 119, respectively, with decent enantioselectivity (Scheme 25) [77]. The formation of an alkylidene carbene 117 and its rapid rearrangement via 1,2-silyl shift (in case of R = silyl group) into the alkylated β-ketoesters 115 can fairly explain the reaction outcome. On the other hand, the ligand

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

• (Scheme 8). After bromination of 40 with molecular bromine in carbon tetrachloride, direct dehydrobromination with lithium chloride in dimethylformamide gave 11 in 85% isolated yield. Müller’s group reported an alternative synthesis for 11 starting from the carbene adduct 41 over two or three steps [55

• sodium salt of 4,5-benzotropone (11) and defined carbene–carbene rearrangements of 77–79 before finally it was verified by trapping of unstable intermediates 77–79 (Scheme 14) [77]. In 2002, McMahon reported obtaining the naphthylcarbene rearrangement manifold via the carbonyl groups of the isomeric

• -triene (78), and triplet 2-naphthylcarbene (79). Formation of allene 83 as an alternative carbene rearrangement product was not detected under the studied photolysis conditions (Scheme 14). Kitahara’s group reported the one-step synthesis of heptafulvalenes and benzoheptafulvalenes from monocyclic

Electrochemically modified Corey–Fuchs reaction for the synthesis of arylalkynes. The case of 2-(2,2-dibromovinyl)naphthalene

• Fabiana Pandolfi,
• Isabella Chiarotto and
• Marta Feroci

Beilstein J. Org. Chem. 2018, 14, 891–899, doi:10.3762/bjoc.14.76

• ) increases the yield of 5a and substitutes 1a (as proton donor) in reaction 2 (Scheme 6). The anion generated by cathodic reduction of dibromoalkene 1a (Scheme 2, reaction 1) can also eliminate bromide (as reported in literature [31]), yielding the corresponding carbene (Scheme 2, reaction 2). This carbene

Cobalt-catalyzed directed C–H alkenylation of pivalophenone N–H imine with alkenyl phosphates

• Wengang Xu and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2018, 14, 709–715, doi:10.3762/bjoc.14.60

• Wengang Xu Naohiko Yoshikai Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore 10.3762/bjoc.14.60 Abstract A cobalt–N-heterocyclic carbene (NHC) catalyst efficiently promotes an ortho C–H

• demonstrated that the combination of a cobalt–N-heterocyclic carbene (NHC) catalyst and a Grignard reagent allows for the arene C–H functionalization with organic halides and pseudohalides under the assistance of nitrogen directing groups [17][22][23][24][25][26][27]. In this connection, Ackermann developed a

Enhanced quantum yields by sterically demanding aryl-substituted β-diketonate ancillary ligands

• Rebecca Pittkowski and
• Thomas Strassner

Beilstein J. Org. Chem. 2018, 14, 664–671, doi:10.3762/bjoc.14.54

• calculations. Experimental Both complexes were characterized by 1H, 13C, and 195Pt NMR spectroscopy, ESIMS, and elemental analysis. Formation of the carbene complexes was verified by the disappearance of the characteristic NCHN proton signal of the imidazolium salt in the 1H NMR experiment. The syntheses of

One-pot sequential synthesis of tetrasubstituted thiophenes via sulfur ylide-like intermediates

• Jun Ki Kim,
• Hwan Jung Lim,
• Kyung Chae Jeong and
• Seong Jun Park

Beilstein J. Org. Chem. 2018, 14, 243–252, doi:10.3762/bjoc.14.16

• ], these carbene precursors have been played an important role in organic chemistry [10][11][12][13][14][15][16][17][18][19][20][21][22]. As shown in Figure 1, sulfur(IV) and sulfur(VI) ylides are stable. The stability of sulfonium ylides is determined by the electron delocalization of the carbanionic

• . Based on previous reports regarding carbene generation from sulfonium ylides [6][85][86], compounds 9a and 9b were reacted with excess MeOH (Scheme 2). Interestingly, 2-pyridyl-substituted N,S-acetal 9b only provided N,O-acetal 9ba via a 1,4-Micheal addition, whereas N,S-acetal 9a was completely

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

Comparative profiling of well-defined copper reagents and precursors for the trifluoromethylation of aryl iodides

• Peter T. Kaplan,
• Jessica A. Lloyd,
• Mason T. Chin and
• David A. Vicic

Beilstein J. Org. Chem. 2017, 13, 2297–2303, doi:10.3762/bjoc.13.225

• facilitate meaningful comparative studies, such as structural and electrochemical ones [2]. N-Heterocyclic carbene (NHC) complexes of copper such as A1 (Scheme 1) were the first well-defined and structurally characterized copper–CF3 complexes that display activity for the trifluoromethylation of aryl halides

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• corresponding E-1 [10] (Scheme 2). Alternatively, the same transformation can be performed with 3 and thiourea derivative 4 in a two-step reaction through intermediate 5 [11] (Scheme 2). The latter, upon treatment with Et3N, generates a carbene [:C(CN)CO2Et], which dimerizes to give E-1a albeit in low yield

• . The dimerization of the same carbene leading to a mixture of E- and Z-1a was observed when ethyl dibromocyanoacetate was treated with equimolar amounts of LiI in DMF at room temperature with the highest reported yield of 83% [12]. The dimethyl ester E-1b was also obtained selectively by treatment of

• converts into the orthoester 10 via insertion into the C–O bond. The reaction mechanism for the formation of 8 and 9 comprises the initial attack of the nucleophilic carbene onto the electron-deficient C atom of E-1b to give an intermediate zwitterion 11. The latter undergoes two competitive reactions. The

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• reaction with α-bromo ketoximes 1 (Scheme 36). The reaction requires a copper catalyst, which transforms the diazo compound 96 into a metal carbene complex 97. The latter reacts with a nitrosoalkene intermediate NSA (formed from α-bromo ketoxime 1) producing isoxazoline 93 with recovery of the catalyst

NHC-catalyzed cleavage of vicinal diketones and triketones followed by insertion of enones and ynones

• Ken Takaki,
• Makoto Hino,
• Akira Ohno,
• Kimihiro Komeyama,
• Hiroto Yoshida and
• Hiroshi Fukuoka

Beilstein J. Org. Chem. 2017, 13, 1816–1822, doi:10.3762/bjoc.13.176

• Ken Takaki Makoto Hino Akira Ohno Kimihiro Komeyama Hiroto Yoshida Hiroshi Fukuoka Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8527, Japan 10.3762/bjoc.13.176 Abstract Thiazolium carbene-catalyzed reactions of 1,2

• ; N-heterocyclic carbene; ring enlargement; Stetter reaction; vicinal polyketone; Introduction N-Heterocyclic carbenes (NHCs) have been indispensable catalysts for organic synthesis, particularly for umpolung of various functional groups [1][2][3][4][5][6][7][8][9]. In the Stetter reaction, NHCs

• = C(O)R1) reacted with enones III in the presence of thiazolium carbene catalysts to give double acylation products IV in good yields [15]. If enones can be replaced by ynones III in the reaction with benzils, alkenes IV having three acyl moieties would be formed directly. Related products were

Pd(OAc)₂/Ph₃P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles

• Dominik Kellner,
• Maximilian Weger,
• Andrea Gini and
• Olga García Mancheño

Beilstein J. Org. Chem. 2017, 13, 1807–1815, doi:10.3762/bjoc.13.175

• a bulky monodentated phosphine (Scheme 1, reaction 1) [32]. More recently, important efforts have been made in order to develop new methodologies towards more effective and selective catalytic systems, such as the introduction of highly active N-heterocyclic carbene (NHC) catalysts reported by

Unpredictable cycloisomerization of 1,11-dien-6-ynes by a common cobalt catalyst

• Abdusalom A. Suleymanov,
• Dmitry V. Vasilyev,
• Valentin V. Novikov,
• Yulia V. Nelyubina and
• Dmitry S. Perekalin

Beilstein J. Org. Chem. 2017, 13, 639–643, doi:10.3762/bjoc.13.62

• species 8. Further, intramolecular 1,2- or 1,4-hydrometallation in 8 produces carbene complexes, which give cyclopropane derivatives 4 and 5. In order to broaden the substrate scope, we studied similar reactions of the tetramethyl-substituted dienyne 1c (Scheme 4). As expected, it produced the cyclohexene

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

• carbene is an outstanding protocol for the synthesis of polyhydroxylated spiro- or fused 1-indanones [49]. Thus, the imidazole-based carbene catalyzed the conversion of phthalaldehydes 72 to dihydroxyspiro[indane-2,1′-isobenzofuran]-3-ones 73, whereas triazole-based carbene catalyzed the conversion of 72

• quaternary center with high diastereoselectivity as a consequence of the Stetter–Aldol–Aldol (SAA) reaction sequence. The Stetter–Aldol–Aldol conversion of the phthaldialdehyde derivatives 75 and o-formyl substituted chalcones 76 using the thiazole based carbene 78 as a precatalyst allowed to obtain spiro

• formation of a variety of 1-indanones and 1-tetralones has been proposed by Ogoshi et al. [53]. Thus, hydroacylation of o-allylbenzaldehyde derivatives 89 in the presence of [Ni(cod)2] and the N-heterocyclic carbene with an It-Bu substituent gave 1-indanones 90a–i in high yields (Scheme 29). In the case of

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• developments using these compounds. Bu3SnH and N-heterocyclic carbene boranes The reductive decyanation of malononitriles to mononitriles using tributyltin hydride/AIBN in benzene was unexpectedly discovered by Curran and Seong [114]. Later, they made a full study and successfully reduced to mononitriles a

• monodecyanated products 69a,b. Bicyclic lactones 70a,b are then obtained in 3 steps in 41% and 51% yields, respectively, from 69a,b. Later Curran’s group discovered that NHC-boryl radicals, generated from NHC-boranes (N-heterocyclic carbene boranes), abstracted the cyano group from various organic nitriles and

• -heterocyclic carbene boranes and super electron donors provide new procedures for the reduction of malononitriles or α-cyanoesters. This opens the possibility to synthetic applications by using these intermediates in the future. Mechanism for the reduction under metal dissolving conditions. Example of

Highly bulky and stable geometry-constrained iminopyridines: Synthesis, structure and application in Pd-catalyzed Suzuki coupling of aryl chlorides

• Yi Lai,
• Zhijian Zong,
• Yujie Tang,
• Weimin Mo,
• Nan Sun,
• Baoxiang Hu,
• Zhenlu Shen,
• Liqun Jin,
• Wen-hua Sun and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 213–221, doi:10.3762/bjoc.13.24

• aryl or alkyl halides include phosphine ligands independently developed by, for example, Buchwald [13][14][15], Hartwig [16][17], Fu [18][19][20], Kwong [21][22][23], Tang [24][25][26][27] and Lundgren [28], and N-heterocyclic carbene ligands due to the inherent strong sigma-donating property [29

Identification, synthesis and mass spectrometry of a macrolide from the African reed frog Hyperolius cinnamomeoventris

• Markus Menke,
• Pardha Saradhi Peram,
• Iris Starnberger,
• Walter Hödl,
• Gregory F.M. Jongsma,
• David C. Blackburn,
• Mark-Oliver Rödel,
• Miguel Vences and
• Stefan Schulz

Beilstein J. Org. Chem. 2016, 12, 2731–2738, doi:10.3762/bjoc.12.269

• ), requiring more than 10 steps each. RCM can shorten the synthesis remarkably, but requires careful selection of the RCM catalyst to control the double bond configuration. For example, Fürstner and Langemann obtained rac-1 in 31:69 (E/Z)-mixture using a Ru-carbene type catalyst similar to a Grubbs I catalyst

Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

• Anna Zaghi,
• Daniele Ragno,
• Graziano Di Carmine,
• Carmela De Risi,
• Olga Bortolini,
• Pier Paolo Giovannini,
• Giancarlo Fantin and
• Alessandro Massi

Beilstein J. Org. Chem. 2016, 12, 2719–2730, doi:10.3762/bjoc.12.268

• ). Keywords: C–C coupling; continuos-flow; diketone; electron-transfer; umpolung; Introduction The polarity reversal (umpolung) of carbonyl compounds by N-heterocyclic carbene (NHC) or cyanide catalysis represents a straightforward strategy for the synthesis of valuable molecules such as, among the many

From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer

• Ming Liu,
• Jan C. Namyslo,
• Martin Nieger,
• Mika Polamo and
• Andreas Schmidt

Beilstein J. Org. Chem. 2016, 12, 2673–2681, doi:10.3762/bjoc.12.264

• (NHC)2][Cl] by coordination with the carbene carbon atom. The anionic N-heterocyclic carbene 1-(2-phenolate)imidazol-2-ylidene gives the complexes [K][Au(NHC−)2], [Rh(NHC−)3] and [Ni(NHC−)2], respectively. Results of four single crystal analyses are presented. Keywords: anionic ligand; carbene

• tautomer; imidazol-2-ylidene; mesoionic compound; mesomeric betaine; Introduction Since the first isolation of a stable N-heterocyclic carbene (NHC) [1] in 1991 this compound class has provided numerous highly efficient ligands of NHC-metal catalysts for cross-coupling reactions [2][3][4][5][6][7

• tautomer under these conditions; unfortunately the addition of less polar solvents induces a precipitation from solution so that detection of the NHC tautomer by NMR spectroscopy is not possible under these conditions. Base screening revealed that the anionic N-heterocyclic carbene 7 can be generated in

A direct method for the N-tetraalkylation of azamacrocycles

• Andrew J. Counsell,
• Angus T. Jones,
• Matthew H. Todd and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2016, 12, 2457–2461, doi:10.3762/bjoc.12.239

• -pyridylmethyl substituted cyclam [38]. In a related approach, Jeong and co-workers have developed an effective heterogenous system that combines a chloroform solution of cyclam and the alkyl halide with solid potassium carbonate (acknowledging the risk of competing carbene formation under these conditions), to

Organometallic chemistry

• Bernd F. Straub,
• Rolf Gleiter,
• Claudia Meier and
• Lutz H. Gade

Beilstein J. Org. Chem. 2016, 12, 2216–2221, doi:10.3762/bjoc.12.213

• mechanism of the Dötz reaction, he found that chromacyclobutene structures were unrealistic intermediates and instead proposed vinylcarbene complexes as much more stable isomers [64][68][88]. Other research projects of his group included the synthesis of ruthenium–carbene complexes with cis-dichloro ligands

• for olefin metathesis catalysis [86][87][90][91][98][99][100][108][132][138][147], the characterization of copper–carbene complexes as intermediates in the cyclopropanation of alkenes [102][106][113][119][120], as well as detailed studies into the mechanism of the hydroformylation of alkenes. An