Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• -substituted iminium groups with electron-rich (hetero)aromatics are known [18][24]. Furthermore, 1-(trifluoromethyl)indenes have recently been generated by cationic cyclization of β-aryl trifluoromethyl enones under superacid conditions [42][43][44]. Styrenes are also known to behave as dienes in [4 + 2

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• bicyclic compound since the double and triple bonds are too distant. In a following paper by Billard and co-workers, the PKR of oxygen-containing 1,7-enynes was assayed, affording trifluoromethylated oxygenated bicyclic enones (Scheme 9) [48]. Under classical stoichiometric conditions (reaction with Co2(CO

• afforded the corresponding products 59 in good to excellent yields (Scheme 36). The authors then studied the elimination of the trifluoromethyl group from this library of PK adducts, building upon their own experience in the field (vide supra, Scheme 34). Thus, by subjecting enones 59 to treatment with DBU

• in wet nitromethane under reflux, clean conjugate addition/detrifluoromethylation was observed, in this case followed by retro-Michael reaction of nitromethane achieving enones 65 in moderate to good yields (Scheme 37). Interestingly, the overall reaction sequence results in the formal inversion of

Fluorohydration of alkynes via I(I)/I(III) catalysis

• Jessica Neufeld,
• Constantin G. Daniliuc and
• Ryan Gilmour

Beilstein J. Org. Chem. 2020, 16, 1627–1635, doi:10.3762/bjoc.16.135

• disclosed (Figure 1B). Seminal reports by Nevado [41][42] and Gouverneur [43] enabled the synthesis of α-fluoroketones and -enones from terminal and internal alkynes, thereby mitigating difluoroketone formation: This is commonly observed in the fluorination of alkynes using stoichiometric electrophilic

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• from that of enones. The latter underwent the [2 + 2] annulation with olefins at their olefinic center to yield cyclobutane derivatives, and rarely undergo oxetane formation completely. The reaction parameters such as solvent affected the balance between the cyclobutane and oxetane formation. Whereas

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• a suitable Michael acceptor 24.2 to obtain the corresponding allylation product 24.3 after a desulfonylation. Enones can also be subject to SET reductions through photoredox catalysis, and this can lead to [2 + 2] cycloadditions [2][108]. Similar intermediates can also be generated through the

Copper-catalysed alkylation of heterocyclic acceptors with organometallic reagents

• Yafei Guo and
• Syuzanna R. Harutyunyan

Beilstein J. Org. Chem. 2020, 16, 1006–1021, doi:10.3762/bjoc.16.90

• in recent years, many strategies have been reported for their highly enantioselective synthesis. However, while catalytic asymmetric C–C bond formations by ACAs of organometallics is a routine procedure for additions to common Michael acceptors, such as enones and enoates, examples of catalytic

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• ratios. Both cyclic (117 and 118) and acyclic (119,120) ketones could be silylated efficiently (Scheme 23). Interestingly, cyclic enones conjugated to an external double bond, as in 121, upon exposure to these conditions resulted in an excellent selectivity for the 1,6-addition and in high ee for product

Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst

• Abhijit Paul,
• Debnath Chatterjee,
• Srirupa Banerjee and
• Somnath Yadav

Beilstein J. Org. Chem. 2020, 16, 140–148, doi:10.3762/bjoc.16.16

• following three categories: (i) by Wittig or Doebner reaction of indoles bearing a 3-aldehyde group; (ii) by 1,4- or 1,2-addition of α,β-enones or carbonyl compounds, followed by oxidation or elimination, respectively; (iii) by Pd-catalysed oxidative coupling of indoles with activated alkenes. Several

Rapid, two-pot procedure for the synthesis of dihydropyridinones; total synthesis of aza-goniothalamin

• Thomas J. Cogswell,
• Craig S. Donald and
• Rodolfo Marquez

Beilstein J. Org. Chem. 2020, 16, 135–139, doi:10.3762/bjoc.16.15

• described above. Rewardingly, Hosomi–Sakurai allylation of the conjugated imine intermediate proceeded to afford the desired diene 10 in working yield (35%). The formation of diene 10 is significant as the corresponding α,β-enones and α,β-enals undergo exclusive conjugate addition under Hosomi–Sakurai

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

• Anna Kmieciak and
• Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

• ], conjugated additions to enones [7], and allylic alkylations [8][9]. Another direction of research is the use of phosphines in organocatalysis [10][11] and bifunctional catalysis [12]. Several methods were developed to introduce the phosphine functionality to organic molecules. The reaction of organometallics

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• acids. In 2014, a Cu(I/II)-catalyzed α-trifluoromethylation of α,β-unsaturated carbonyl compounds were unfolded by the Bi group (Scheme 77) [140]. The reaction was applied to a broad range of carbonyl compounds, including enones, α,β-unsaturated esters, thioesters, and amides. Notably, the authors

A review of the total syntheses of triptolide

• Xiang Zhang,
• Zaozao Xiao and
• Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

• enones [51]. Photoexcitation (UV, 365 nm) of [Au-Au]2+ generated [Au-Au]2+*, which could then effectively reduce the vinyl C–Br bond via a SET to generate the vinyl radical. This radical then cyclizes with an aryl group to generated a tricyclic intermediate bearing a tertiary radical. A simultaneous

Synthesis of non-racemic 4-nitro-2-sulfonylbutan-1-ones via Ni(II)-catalyzed asymmetric Michael reaction of β-ketosulfones

• Alexander N. Reznikov,
• Anastasiya E. Sibiryakova,
• Marat R. Baimuratov,
• Eugene V. Golovin,
• Victor B. Rybakov and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2019, 15, 1289–1297, doi:10.3762/bjoc.15.127

• reactions. Thus, ketonitrosulfones were obtained with good enantiomeric excesses via asymmetric addition of α-nitrosulfones to enones in the presence of organocatalysts [41]. Asymmetric addition of β-ketosulfones to nitroalkenes was implemented using various organocatalysts [42]. The reaction of

Robust perfluorophenylboronic acid-catalyzed stereoselective synthesis of 2,3-unsaturated O-, C-, N- and S-linked glycosides

• Madhu Babu Tatina,
• Xia Mengxin,
• Rao Peilin and
• Zaher M. A. Judeh

Beilstein J. Org. Chem. 2019, 15, 1275–1280, doi:10.3762/bjoc.15.125

• -tetra-O-acetyl-D-glucal (4a) to enosides are limited in the literature and pose special challenges including low product yields and selectivities, the need for a large excess of the catalyst and formation of by-products such as furaldehydes and enones [1][33][34][35]. Enosides are important building

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• cyclopropanols 91 derived from Kulinkovich cyclopropanation into linear enones 147 was developed by Wu and co-workers [121]. The approach features the regioselective cleavage of the cyclopropane rings in EtOH at room temperature with cheap and readily available Co(acac)2 as the catalyst and air as the reagent

• . Ag(I)-catalyzed ring-opening and acylation of cyclopropanols with aldehydes. Aerobic oxidation ring-opening of cyclopropanols for the synthesis of 2-oxyranyl ketones. Aerobic oxidation ring-opening of cyclopropanols for the synthesis of linear enones. Aerobic oxidation ring-opening of cyclopropanols

Cross metathesis-mediated synthesis of hydroxamic acid derivatives

• Shital Kumar Chattopadhyay,
• Subhankar Ghosh and
• Suman Sil

Beilstein J. Org. Chem. 2018, 14, 3070–3075, doi:10.3762/bjoc.14.285

• CM-mediated synthesis of functionalized alkenes of various kinds continue to appear. For example, cross metathesis with acrylates [8][9][10], α,ß-unsaturated acid chlorides [11], acrylamides [12][13][14], vinyl sulfones [15], vinylphosphine oxides [16], vinyl phosphonates [17], enones [18], and

Synthesis of indole–cycloalkyl[b]pyridine hybrids via a four-component six-step tandem process

• Muthumani Muthu,
• Rakkappan Vishnu Priya,
• Abdulrahman I. Almansour,
• Raju Suresh Kumar and
• Raju Ranjith Kumar

Beilstein J. Org. Chem. 2018, 14, 2907–2915, doi:10.3762/bjoc.14.269

• –C bond forming reaction [57] and three-component reactions of aromatic aldehydes, 3-(1H-indol-3-yl)-3-oxopropanenitrile and malononitrile [58][59], 2-acetylpyridine [60] or 3-amino-2-enones [61]. Incidentally, the indole scaffold is found in several natural products and bioactive synthetic compounds

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• intermediates in the synthesis of pharmaceuticals and various chemical entities such as allylic alcohols, benzoxathiepines, benzotiazepines, α-thioketones, α-substituted α,β-unsaturated enones, and β-hydroxysulfoxides [15]. Accordingly, a number of methodologies have been reported for their synthesis

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

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

• synthesis of monofluoroalkenes from α-fluoro-α,β-unsaturated aldehydes 45, which are more easily accessible than the corresponding enones (Scheme 10) [38]. Their synthesis started with the olefination of aldehyde 43 which gave the corresponding monofluoroalkene 44. Reduction with subsequent oxidation of the

Preparation of imidazo[1,2-a]-N-heterocyclic derivatives with gem-difluorinated side chains

• Layal Hariss,
• Kamal Bou Hadir,
• Mirvat El-Masri,
• Thierry Roisnel,
• René Grée and
• Ali Hachem

Beilstein J. Org. Chem. 2017, 13, 2115–2121, doi:10.3762/bjoc.13.208

• propargylic derivatives 4 [28] with aromatic aldehydes. Then, the DBU-mediated isomerization afforded the desired enones 6a–e in 21–66% yields (Scheme 2 and Table 1). For the synthesis of the desired nitrogen heterocycles, we started our study by reacting 6a with 2-aminopyridine in the presence of AlCl3 and

• % yield (Table 2, entry 1). Having these optimized conditions in hand, and to explore the substrate scope, different substituted 2-aminopyridines were successfully employed to afford the tandem oxidative cyclization products 7 in 32–65% yields. On the other hand, enones 6 with two different R groups

• heteroaromatic frameworks would be of much interest for biological studies in different areas of life sciences. Experimental Representative procedure for the synthesis of imidazopyridine 7a The syntheses of propargylic fluorides 5 and enones 6 were performed in a similar way as described before [26]. Synthesis

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

• -diketones and 1,2,3-triketones with enones and ynones have been investigated. The diketones gave α,β-double acylation products via unique Breslow intermediates isolable as acid salts, whereas the triketones formed stable adducts with the NHC instead of the coupling products. Keywords: Breslow intermediate

• = 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

• recently obtained by the dimsyl anion-promoted double acylation of enones with benzils, followed by dehydrogenation of the resulting alkanes in one pot [16]. Moreover, if the reaction of cyclic 1,2-diketone I (G = C(O)R1) with activated alkenes may take place similarly, this reaction could be utilized as a

Cycloheximide congeners produced by Streptomyces sp. SC0581 and photoinduced interconversion between (E)- and (Z)-2,3-dehydroanhydrocycloheximides

• Li Yang,
• Ping Wu,
• Jinghua Xue,
• Huitong Tan,
• Zheng Zhang and
• Xiaoyi Wei

Beilstein J. Org. Chem. 2017, 13, 1039–1049, doi:10.3762/bjoc.13.103

• likely a photochemical process as it is known that most Z/E isomerizations of carbon double bonds in conjugated olefins and α,β-enones are facilitated by this process [12][13][14]. However, as all experiments in the present study were carried out either in the dark (fermentation) or under indoor light

• correspond to stable 1(n–π*) and 3(π–π*) states of α,β-enones [14], respectively, and the T1 planar maxima, with increased the C1–O1 and C6–Cα bond lengths and a decreased C1–C6 bond length relative to those of T1 minima, show similarity to a T2 π–π* species [14]. Comparison of parameters of geometries in

• those proposed for isomerization of the C–C double bond in acyclic α,β-enones [14][17], but more complicated in details. Due to the presence of two T1 minima and two S0 maxima, there are two equivalent points for the second ISC, one around Φ = 90° the other around Φ = −90°, and two points being with

Metal-free hydroarylation of the side chain carbon–carbon double bond of 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles in triflic acid

• Anna S. Zalivatskaya,
• Dmitry S. Ryabukhin,
• Marina V. Tarasenko,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya,
• Elena V. Grinenko,
• Ludmila V. Osetrova,
• Eugeniy R. Kofanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2017, 13, 883–894, doi:10.3762/bjoc.13.89

• rise to the corresponding unstable highly reactive dications D, which were not detected by NMR. It should be mentioned, that there have been reports [37][54][55][56][57] on NMR observations of O,C-diprotonated forms (dications) of conjugated enones in superacidic medium, which are structurally close to

Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition

• Matthew A. Horwitz,
• Elisabetta Massolo and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2017, 13, 762–767, doi:10.3762/bjoc.13.75

• ] nucleophiles using bifunctional cinchona alkaloid catalysts. The Sasai and Enders groups used a phosphinothiourea to enable a Rauhut–Currier reaction to form bicyclic enones [16]. The Tian and Lin group used alkyne-tethered cyclohexadienones in an arylrhodation/conjugate addition sequence that