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

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

• evident from the 3D structure of the proposed intermediate 6 (see Supporting Information File 1). In the case of 1i–k the electron acceptor effects or the restricted rotation of conjugated enones could be the problem. The case of dienyne 1l was particularly surprising as it seemed to have a very similar

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

• -promoted α-methylenation of compounds 118 followed by cyclization of the resulting enones 119 allowed to obtain a series of 2-alkyl-1-indanones 120 in very good yields (Scheme 38). A stereoselective, catalytic, tandem transformation of α,β-unsaturated arylketones 121 to fluorine-containing 1-indanone

• synthesized halogenated 1-indanones 253 from 2-halogenocyclopent-2-enones 252 and diene 251 [99]. As a result of the Diels–Alder reaction, bromo- and chloro-substituted 1-indanones 253a and 253b have been obtained in 91% and 72% yield, respectively (Scheme 70). Harmata et al. have synthesized 1-indanones 257

• 276 [106]. The new catalytic reaction which replaced a previously described four-step synthesis [107], involved a tandem aldol condensation/dehydration and cyclization of the intermediate 275 to 276 (Scheme 77). In 1999, Ikeda and Mori have presented a cyclotrimerization of enones (e.g

Solid-phase enrichment and analysis of electrophilic natural products

• Frank Wesche,
• Yue He and
• Helge B. Bode

Beilstein J. Org. Chem. 2017, 13, 405–409, doi:10.3762/bjoc.13.43

• extracts via their reactivity against azide as a nucleophile followed by their subsequent enrichment using a cleavable azide-reactive resin (CARR). Using this approach, natural products carrying epoxides and α,β-unsaturated enones as well as several unknown compounds were identified in crude extracts from

• -guided introduction of an azide functionality into electrophilic natural products and the subsequent azide enrichment on a solid phase facilitates the detection of epoxides and α,β-unsaturated enones in XAD extracts of Photorhabdus. Epoxystilbene (1) and glidobactins have never been observed before in

Et₃B-mediated and palladium-catalyzed direct allylation of β-dicarbonyl compounds with Morita–Baylis–Hillman alcohols

• Ahlem Abidi,
• Yosra Oueslati and
• Farhat Rezgui

Beilstein J. Org. Chem. 2016, 12, 2402–2409, doi:10.3762/bjoc.12.234

• addition of Grignard reagents onto α-methyl cyclic enones, affording mainly the trans-2,3-disubstituted cyclohexanones as being the thermodynamic products [52]. Similarly, we believe that the intramolecular conjugate addition of carbanion 3j onto α-substituted enone moiety is under thermodynamic control

Highly chemo-, enantio-, and diastereoselective [4 + 2] cycloaddition of 5H-thiazol-4-ones with N-itaconimides

• Shuai Qiu,
• Choon-Hong Tan and
• Zhiyong Jiang

Beilstein J. Org. Chem. 2016, 12, 2293–2297, doi:10.3762/bjoc.12.222

• [6], allylation [7], conjugate addition to enones [8], and γ-addition with allenoates [9]. All these examples focused on nucleophilic addition reactions of the C5 atom of 5H-thiazol-4-ones. Recently, we described an organocatalytic asymmetric [4 + 2] cyclization of 5H-thiazol-4-ones with a series of

A new and expeditious synthesis of all enantiomerically pure stereoisomers of rosaprostol, an antiulcer drug

• Wiesława Perlikowska,
• Remigiusz Żurawiński and
• Marian Mikołajczyk

Beilstein J. Org. Chem. 2016, 12, 2234–2239, doi:10.3762/bjoc.12.215

• reported the first strategy for the synthesis of the enantiomerically pure rosaprostol stereoisomers 1a–d using the diastereoisomerically pure camphor-protected 3-[(dimethoxyphosphoryl)methyl]-4,5-dihydroxycyclopent-2-enones (−)-2a and (+)-2b as chiral building blocks (Scheme 1) [24]. These compounds can

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• the synthesis of functionalized ketones and alcohols, including γ-hydroxy enones. The Dakin oxidation finds application for the synthesis of phenols from arylaldehydes or aryl ketones and the Elbs persulfate oxidation allows the preparation of hydroxyphenols from phenols. Finally, the Schenck and

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

• to both of the carbonyl oxygens. During the course of studying the addition of aromatic thiols to α,β-unsaturated benzamides and enones, Chen, Ding, and Wu first reported the conjugate addition of thiophenol (23) to N-methacryloyl benzamide 91 followed by enantioselective protonation using Takemoto’s

• nucleophiles some common selectivity trends were observed. Aromatic enones (R2 = aryl) generally provided higher levels of enantioselectivity than aliphatic enones (R2 = alkyl). Additionally, for all of the nucleophiles, except thiols, increasing the steric bulk at R1 resulted in diminished enantioselectivity

• . Building on his asymmetric conjugate additions to α-substituted enones, Luo demonstrated that Hantzsch ester 133 chemoselectively reduces activated alkenes 132 in the presence of α-substituted vinyl ketones 118, generating carbon nucleophiles 135 in situ. These nucleophiles then reacted with the α

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

• the pionnering work by Trost in 2004 [26], several examples of the utility of the structurally related oxazol-4(5H)-ones (Figure 1b, X = O) have also been published, which involve mainly Michael additions (to enones [27][28], nitroalkenes [29][30], alkynones [31][32][33] and vinyl sulfones [34]), γ

• )-ones 1 as pronucleophiles in organocatalyzed Michael addition reactions 2-Thio-1H-imidazol-4(5H)-ones 1 (R = SBn) have been reported to be effective equivalents of N-subtituted (alkyl, aryl, allyl) α-amino acids in conjugate addition reactions to both, nitroalkenes and α-silyloxy enones as Michael

• been very scarcely used as pronucleophiles in asymmetric catalysis. Only few examples have been reported, some of them involving the use of rhodanines of type 44 (Scheme 7a), which act directly as pronucleophiles against enones [78] (Scheme 7a,1), enals [79] (a,2) and azodicarboxylates [80] (a,3). In