Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov,
• Olesya V. Khoroshilova and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• , D2SO4), (arysulfonyl)allenes (ArSO2–CR1=C=CR2R3) and (arylsulfinyl)allenes (ArSO–CR1=C=CR2R3) undergo cyclization into the corresponding stable 1,2-oxathiolium ions, which were studied by means of NMR and DFT calculations. Quenching of solutions of these cations with low nucleophilic media, aqueous HCl

• , leads to their deprotonation with a stereoselective formation of (arysulfonyl)butadienes (for instance, ArSO2–CR1=C–C(Me)=CH2, for R2 = R3 = Me, yields of 87–98%). Reactions of (arysulfonyl)allenes in the system TfOH (0.1 equiv)–HFIP (hexafluoropropan-2-ol) followed by hydrolysis give rise to allyl

• alcohols (ArSO2–CR1=CH–C(OH)R2R3, yields of 78–99%). Reflux of solutions of (arysulfonyl)allenes in the presence of TfOH (1 equiv) in 1,2-dichlorobenzene leads to the cyclization into thiochromene 1,1-dioxides in high yields. Under the action of TfOH or AlX3 (X = Cl, Br) followed by hydrolysis of reaction

Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety

• Alex Frichert,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2018, 14, 2461–2467, doi:10.3762/bjoc.14.222

• beginning, and of precursors in which one of the centers will be sp2- and the other sp3-hybridized. Examples of the latter have already been obtained in form of allenes 32 and 34 that will now have to be elaborated further. Bicyclic eunicellane-type diterpenes. Synthetic eunicellane-type compounds with

• McMurry coupling to the diol, followed by two-step epimerization at C2. Assembly of the envisaged cyclization precursor 27. Structure analysis of diastereomeric cyanohydrins 29 and 30. Formation of allenes 32 and 34 from sterically crowded propargylic alcohol 31. Supporting Information Supporting

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• using alkynes [63][64][65][66], alkenes [67][68], allenes [69][70][71] and 1,3-dienes [72][73] have been reported. In this regard, Mikami et al. reported the Rh-catalyzed hydrocarboxylation of styrene derivatives depicted in Scheme 33 [74]. The desired reaction proceeded using [RhCl(cod)]2 as a catalyst

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• alkenes, which required a stoichiometric amount of oxidant. Herein, we wish to review the cobalt-catalyzed hydroarylation of alkynes, alkenes, allenes, enynes, imines, and isocyanates. These reactions usually proceed via either an oxidative addition of Ar–H to a low-valent cobalt to form A1 intermediate

• succinimides 50 in good yields (Scheme 31a) [87]. Likewise, oximes 51 [88] were also efficient participated in the hydroarylation of maleimides (Scheme 31b). 3. Hydroarylation of allenes An allene is an exceptional functional group in organic synthesis due to its cumulative double bonds [89][90]. In this

• context, Ackermann and co-workers developed a coupling reaction of arenes 53 with allenes to give hydroarylation products 54 (Scheme 32) [91]. The merits of the reaction are broad scope including a variety of arenes and allenes, and high atom economy. Based on the mechanistic studies and DFT calculations

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

• the conversion of allenes 20. A regioselective 1,2-addition on the internal π-bond was observed to afford the products 21, because of the presence of a heteroatom substituent that can stabilize the radical or cationic intermediate by coordination with the copper complex (Scheme 9) [42]. However, the

• efficiency of the reaction is limited by the need to use 2 equivalents of allenes 20 to obtain good yields. λ3-Iodane reagents: alkynylbenziodoxolone Ethynylbenziodoxolone (EBX) is a powerful reagent to perform the electrophilic alkynylation of various functional groups such as carbonyl derivatives, thiols

• -trifluoromethylation of dienes. Catalytic benzoyloxy-trifluoromethylation of allylamines. Catalytic benzoyloxy-trifluoromethylation of enynes. Catalytic benzoyloxy-trifluoromethylation of allenes. Alkynylation of N-(aryl)imines with EBX for the formation of furans. Catalytic benzoyloxy-alkynylation of diazo compounds

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

• iodides, allenes, and aldehydes has been developed to afford multi-substituted homoallylic alcohols in a diastereoselective manner. Control experiments for understanding the reaction mechanism reveal that the cobalt catalyst is involved in the oxidative addition and carbometalation steps in the reaction

• 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

• -selectivity because of meta- and ortho-substituted aryl iodides also being well tolerated in the reaction. The protocol was not only limited to the coupling of simple allenes; it was also used with heteroatom-containing functionalized allenes to afford the syn-homoallylic alcohols 4u, 4u’ and 4w in reasonably

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

Chlorination of phenylallene derivatives with 1-chloro-1,2-benziodoxol-3-one: synthesis of vicinal-dichlorides and chlorodienes

• Zhensheng Zhao and
• Graham K. Murphy

Beilstein J. Org. Chem. 2018, 14, 796–802, doi:10.3762/bjoc.14.67

• pathways. For example, Liu and co-workers used Togni’s benziodoxolone reagent [35] in a radical-mediated vicinal 2,3-difunctionalization of allenes, which proceeded via CF3-radical adduct A (Scheme 1a) [36]. In contrast, Muñiz reported that with PhI(NTs2)2, an oxidative amination occurred via cation B

• ranging from 1.2–4.3:1 Z:E. α-Substituents on the allenes were equally viable, as 1,1-diphenylallene gave 3j in 84% yield, and the related mono-methyl and mono-chloro derivatives 2k and 2l gave dichlorides 3k and 3l in 79% and 56% yield, respectively, with little preference observed for formation of

• previously obtained, suggesting that ionic processes were operative. Furthermore, since no evidence of propargyl chlorides or α-dichloromethylstyrenes were observed, it appears the chlorination of allenes with 1a proceeded without interruption of 1,2-phenyl shifts or iodane elimination, resulting in a

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• corresponding analogues from primary propargylic chlorides (Scheme 14), while the trifluoromethylated allenes can be obtained from reactions of secondary propargylic chlorides. Moreover, in 2014, the primary and secondary benzylic chlorides [28] were investigated under similar conditions, which proceeded

• that substrates bearing sulfonate group had a high reactivity. Recently, the group of Xiao and Lin [65] developed a copper-catalyzed C–H trifluoromethylation of 3-arylprop-1-ynes to provide (trifluoromethyl)allenes and propargyl trifluoromethanes (Scheme 44). This reaction was the first reported

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• multicomponent reactions Transition metals, especially Pd and Cu, are well-known catalysts for multicomponent reactions. Carbopalladation reactions of allenes, alkynes and carbon monoxide are very important processes in multicomponent syntheses. Additionally, copper-catalyzed multicomponent reactions such as

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• nitroalkene [67]. α,β-Unsaturated phosphonates and phosphine oxides Transition metal catalysts In 2006, Hayashi and co-workers reported the first conjugate addition–enantioselective protonation of allenes 165 bearing a phosphine oxide (Scheme 39) [68]. Incorporation of the phosphine oxide allowed for

• selective protonation forming the less stabilized terminal chiral alkene 166 over the internal achiral isomer 167, an inherent challenge in the hydroarylation of terminal allenes. Electron-rich, neutral, and electron-poor arylboronic acids 47 added to alkyl (R = Me, Et, n-Bu) diphenylphosphinylallenes 165

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• were used for the reaction. The phenolic hydroxy group of the catalyst was thought to be crucial in controlling the enantioselectivity by forming hydrogen bonds with reactants. Besides, enantioselective additions of allenes to isatins were also achieved under these conditions, giving the desired

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

• Antonia Mielgo and
• Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

• ] pronucleophiles to γ-substituted allenoates and/or alkynoates in the presence of a C2-symmetric chiral phosphine catalyst. Although γ-substituted allenes have been employed in many phosphine-mediated γ-additions, to date there was virtually no progress on the use of prochiral pronucleophiles in phosphine-mediated

Solving the puzzling competition of the thermal C²–C⁶ vs Myers–Saito cyclization of enyne-carbodiimides

• Anup Rana,
• Mehmet Emin Cinar,
• Debabrata Samanta and
• Michael Schmittel

Beilstein J. Org. Chem. 2016, 12, 43–49, doi:10.3762/bjoc.12.6

• -allenes [12][13][14][15][16][17], and enyne-carbodiimides [18][19][20][21][22][23][24][25] have received great interest over the last two decades due to their value for organic synthesis and their interesting mechanistic facets [26]. Like for enyne-allenes, the cyclization mode of enyne-carbodiimides 1

Facile synthesis of 4H-chromene derivatives via base-mediated annulation of ortho-hydroxychalcones and 2-bromoallyl sulfones

• Srinivas Thadkapally,
• Athira C. Kunjachan and
• Rajeev S. Menon

Beilstein J. Org. Chem. 2016, 12, 16–21, doi:10.3762/bjoc.12.3

• furnished 3-arylsulfonyl-4H-chromene derivatives in 58–67% yield (18 examples). 2-Bromoallyl sulfones functioned as synthetic surrogates for allenyl sulfones in the reaction. Keywords: allenes; chromenes; cyclocondenzation; sulfones; vinylic substitution; Findings Benzo[b]dihydropyran, commonly known as

Pyridylidene ligand facilitates gold-catalyzed oxidative C–H arylation of heterocycles

• Kazuhiro Hata,
• Hideto Ito,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2015, 11, 2737–2746, doi:10.3762/bjoc.11.295

• arylation; gold catalysis; Introduction Over the past decade, gold salts and complexes have emerged as unique catalysts for the transformation of alkynes, alkenes and allenes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. In most of the gold

Copper-catalyzed aminooxygenation of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives

• Yan Li,
• Xue Zhou,
• Guangfan Zheng and
• Qian Zhang

Beilstein J. Org. Chem. 2015, 11, 2721–2726, doi:10.3762/bjoc.11.293

• amination of allenes [46]. Encouraged by these results, we try to develop copper-catalyzed aminooxygenation of alkenes by using NFSI. Herein, we report a simple and efficient copper-catalyzed three-component aminooxygenation reaction of styrenes with NFSI and N-hydroxyphthalimide (NHPI) derivatives (Scheme

Recent advances in copper-catalyzed asymmetric coupling reactions

• Fengtao Zhou and
• Qian Cai

Beilstein J. Org. Chem. 2015, 11, 2600–2615, doi:10.3762/bjoc.11.280

• improved to 92% ee with a new chiral catalyst (Scheme 25) [65]. In 2012, Hoveyda and Jung reported a copper/NHC-catalyzed asymmetric allylic substitution of allyl phosphates with allenylboronates [66], leading to chiral allenes bearing a tertiary or quaternary carbon stereogenic center in high yields and

Synthesis of constrained analogues of tryptophan

• Elisabetta Rossi,
• Valentina Pirovano,
• Marco Negrato,
• Giorgio Abbiati and
• Monica Dell’Acqua

Beilstein J. Org. Chem. 2015, 11, 1997–2006, doi:10.3762/bjoc.11.216

• reactions between 2-vinylindoles as 4π-components with activated dienophiles and allenes [18][19][20][21]. The reported methodologies allowed for the synthesis of substituted derivatives with excellent degrees of selectivity. Starting from these results, we envisaged that 3-amino-1,2,3,4-tetrahydrocarbazole

• reactivity upon specific substitution patterns at the indole nucleus were observed by us in competitive Diels–Alder cycloaddition/Michael addition reactions of vinylindoles with classical dienophile and in competitive cycloaddition/hydroarylation reactions with allenes, see [20][21] for a more detailed

An efficient synthesis of N-substituted 3-nitrothiophen-2-amines

• Sundaravel Vivek Kumar,
• Shanmugam Muthusubramanian,
• J. Carlos Menéndez and
• Subbu Perumal

Beilstein J. Org. Chem. 2015, 11, 1707–1712, doi:10.3762/bjoc.11.185

• assembled from acyclic starting materials by methods such as i) reaction of lithiated 1-alkynes or allenes with substituted phenyl isothiocyanates [20], ii) treatment of N-allylbenzotriazole with substituted phenylisothiocyanates [21] and iii) reaction between phenyl isothiocyanate and electron-deficient

• allenes catalyzed by PPh3 [22] (Scheme 1a–c). On the other hand, studies on the synthesis of 3-nitrothiophenes are scarce. One of the traditional methods involves electrophilic aromatic substitution reactions of thiophenes, which introduces substituents at the 2- and 5-positions, but with some drawbacks

Why base-catalyzed isomerization of N-propargyl amides yields mostly allenamides rather than ynamides

• Armando Navarro-Vázquez

Beilstein J. Org. Chem. 2015, 11, 1441–1446, doi:10.3762/bjoc.11.156

• the yncarbamate 13c. The difference in the N-allenyl → N-alkynyl gap for 12 and 13 could be partially attributed to the different basal conformations adopted by allenes 12b and 13b whereas the methynic proton in the benzylic chain respectively prefers an anti or syn conformation with respect to the N

Synthesis of γ-hydroxypropyl P-chirogenic (±)-phosphorus oxide derivatives by regioselective ring-opening of oxaphospholane 2-oxide precursors

• Iris Binyamin,
• Shoval Meidan-Shani and
• Nissan Ashkenazi

Beilstein J. Org. Chem. 2015, 11, 1332–1339, doi:10.3762/bjoc.11.143

• unique interest from a synthetic point of view due to their ability to create new phosphines [48] or to be involved in various reactions (e.g., [2 + 3] cycloaddition) [49][50]. Moreover, propargyl compounds are known to undergo base catalyzed 1,3-prototropic rearrangments to the corresponding allenes [51

Regioselective synthesis of chiral dimethyl-bis(ethylenedithio)tetrathiafulvalene sulfones

• Flavia Pop and
• Narcis Avarvari

Beilstein J. Org. Chem. 2015, 11, 1105–1111, doi:10.3762/bjoc.11.124

• previously observed only in bismuth wires and carbon nanotubes [13]. Another interesting research area is the redox modulation of the chiroptical properties described in derivatives such as TTF-allenes [14], TTF-helicenes [15], or TTF-paracyclophanes [16]. Thus, to address the different opportunities offered

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

• (ΔG‡ = 180 kJ mol−1 for CH3CH=C=CHCH3) [11]. In contrast, several allenes directly connected with electron-donating groups occasionally underwent photoracemization [12][13]. Although the mechanism of the photoracemization is not clear, a comparative examination of the racemization rate in 1 and 2, the

• of the C=C=C unit at 1914 cm−1. Because new symmetrical allenes were subject to optical resolution, the separation of (rac)-3 was carried out by using a recycling HPLC method on a chiral stationary phase (DAICEL Chiralpak IA-3) with hexane/CHCl3/EtOH (v/v = 20:10:0.2) elution. Thus, equimolecular

• amounts of the optically pure allenes (+)-3 and (−)-3, whose optical rotations ([α]D25) are +726 (c 0.853 in CH2Cl2) and −721(c 0.853 in CH2Cl2), respectively, were collected. Similarly, optical resolution of (rac)-9 also provided (+)/(−)-9 with optical rotations ([α]D25) of +338 (c 0.83 in CH2Cl2) and

Anionic sigmatropic-electrocyclic-Chugaev cascades: accessing 12-aryl-5-(methylthiocarbonylthio)tetracenes and a related anthra[2,3-b]thiophene

• Laurence Burroughs,
• John Ritchie,
• Mkhethwa Ngwenya,
• Dilfaraz Khan,
• William Lewis and
• Simon Woodward

Beilstein J. Org. Chem. 2015, 11, 273–279, doi:10.3762/bjoc.11.31

• eliminations. Structural packing motifs and electronic properties are reported for the tetracenes. Keywords: allenes; anionic Chugaev rearrangement; anionic sigmatropic rearrangement; tetracene properties; X-ray structures; Introduction In recent years polyacenes, especially tetra- and pentacenes, have been

• cascade approach for rapid access to tetracene sulfoxides in 2007 (Scheme 1). In 2012 Liu used a Pd-based strategy to provide 12-substituted 5-aryltetracenes [after final trapping with RB(OH)2)] [16]. Both of these reactions rely on the formation of bis-allenes 2, attained by Lin through 2,3-sigmatropic

• very efficient routes to tetracene derivatives containing one or more thiolate (SH) groups for the use in highly electrically conducting organics. In this regard we were attracted by a single result in the early literature [17] showing that traces of allenes related to 2 (X = SCOSMe) were accessible