A modular approach to neutral P,N-ligands: synthesis and coordination chemistry

• Vladislav Vasilenko,
• Torsten Roth,
• Clemens K. Blasius,
• Sebastian N. Intorp,
• Hubert Wadepohl and
• Lutz H. Gade

Beilstein J. Org. Chem. 2016, 12, 846–853, doi:10.3762/bjoc.12.83

• hydrogenations [1][2] and allylic substitutions [3][4] to Heck reactions [5] and conjugate additions to enones [6]. Their popularity arises from the inherent electronic disparity of the phosphorus and the nitrogen donor groups, rendering one binding site a soft π-acceptor featuring a pronounced trans effect and

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• a variety of transformations. Utilizing the primary amine-thiourea 18, an enantioselective formal aza-Diels–Alder reaction of enones 12 and 13 was reported. In this reaction the enamine is formed from the side of the methyl ketone, which is conjugated with the pre-existing double bond, providing the

• cycloalkanones using catalyst 11 [18]. The enantioselective synthesis of indolo- and benzoquinolidine compounds through aza-Diels–Alder reaction of enones with cyclic imines [19]. Enantioselective [5 + 2] cycloaddition [20]. Asymmetric synthesis of oxazine derivatives 26 [21]. Asymmetric synthesis of bicyclo

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

• Laura A. Bryant,
• Rossana Fanelli and
• Alexander J. A. Cobb

Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46

• -branched enones 47 via iminium ion catalysis (Scheme 12) [47]. This study found that the catalytic function could be modulated to induce diastereodivergent pathways by applying an external chemical stimulus (Scheme 12). Several conclusions were made from this study, one of which was that the hydrogen

• vinylogous Michael addition reaction [48]. In this process, cyclic enones 52 are added to nitroalkenes 41 using dienamine catalysis (Scheme 13). Although no model is suggested with respect to how the 6’-OH is involved, it is clearly of importance as the analogous 6’-OMe derived cupreine catalyst gives

• significantly lower conversions and selectivities. Simpkins and co-workers have used CPD-30 in the reaction of triketopiperidines (TKPs) 54 with a variety of enones with very good selectivity (Scheme 14a) [49]. Interestingly, with different types of acceptor, a cyclization event occurred leading to the bicyclic

Study on the synthesis of the cyclopenta[f]indole core of raputindole A

• Nils Marsch,
• Mario Kock and
• Thomas Lindel

Beilstein J. Org. Chem. 2016, 12, 334–342, doi:10.3762/bjoc.12.36

• this investigation. An efficient route to a series of 1,5-di(indol-6-yl)pentenones was developed via Mo/Au-catalyzed Meyer–Schuster rearrangement of tertiary propargylic alcohol precursors. However, none of the enones underwent the desired Nazarov cyclization to a cyclopenta[f]indole. More suitable

• reaction [34]. By installation of a triflyloxy group in the indole 5-position, Pd-catalyzed cyclization also would become possible. As an alternative to the cyclization of enones, Lewis acid-induced cyclizations of allylic alcohols could afford the desired cyclopenta[f]indole system (C, D). Here, it was

Copper-catalyzed asymmetric conjugate addition of organometallic reagents to extended Michael acceptors

• Thibault E. Schmid,
• Sammy Drissi-Amraoui,
• Christophe Crévisy,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 2418–2434, doi:10.3762/bjoc.11.263

• enantioselectivity was recorded (25 formed in a 40% ee). An additional study dealing with the Cu/DiPPAM-based system in the 1,6-addition demonstrated remarkable nonlinear effects (NLE) [20], which could also be observed in 1,4-ACA on both cyclic and acyclic enones. The efficiency of this copper-based catalytic

• cyclic enones. Enynone 69 was reacted to assess the versatility of the reaction, and a full 1,4-regioselectivity was recorded, leading to compound 70 in 71% yield and 91% ee (Scheme 19). Another example of trialkylaluminium addition onto a cyclic extended Michael acceptor was reported in 2013, using a

Stereoselective synthesis of hernandulcin, peroxylippidulcine A, lippidulcines A, B and C and taste evaluation

• Marco G. Rigamonti and
• Francesco G. Gatti

Beilstein J. Org. Chem. 2015, 11, 2117–2124, doi:10.3762/bjoc.11.228

• oxidation of 8 to give the enone 1 in DMSO at high temperature (80 °C) resulted unsuccessful [24]. The hydrogenation of silyl enol ether derivatives in the presence of the IBX-N-oxide complex gives the corresponding enones, usually with better conversion and under milder conditions (room temperature) [25

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• utilized the RRM and the enyne RRM to generate various polycyclic scaffolds. In this context, enones, such as 121a and 121b were assembled easily from dicyclopentadiene derivative 119. Later, these componds were subjected to a RRM to generate the tricyclic enones 122a and 122b, respectively. To this end

• tricyclic enones 122a and 122b. Synthesis of tricyclic and tetracyclic systems via RRM protocol. RRM protocol towards the synthesis of tetracyclic systems. RRM of the propargylamino[2.2.1] system. RRM of highly decorated bicyclo[2.2.1] systems. RRM protocol towards fused tricyclic compounds. RRM protocol to

The simple production of nonsymmetric quaterpyridines through Kröhnke pyridine synthesis

• Isabelle Sasaki,
• Jean-Claude Daran and
• Gérard Commenges

Beilstein J. Org. Chem. 2015, 11, 1781–1785, doi:10.3762/bjoc.11.193

• building blocks in metallo-supramolecular chemistry; however, their synthesis requires the preparation of sensitive building blocks. We present here three examples of nonsymmetric quaterpyridines that were easily obtained in yields of 70–85% by condensation of commercially available enones with 6-acetyl

• step leading to the corresponding acylpyridinium iodide 5, the asymmetric ligands 6–8 were obtained by condensation with various α,β-unsaturated enones with good to excellent yield (see Supporting Information File 1 for the full experimental data). Von Zelewsky et al. showed that pinene-based chirality

• accomplished through the simple synthesis of 6-acetyl-2,2’:6’,2”-terpyridine. After the preparation of the corresponding pyridinium salt, the subsequent condensation with enones led to the desired quaterpyridines. The methyl groups on the pyridine ring are potential grafting points, which can be used without

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

• components, decarboxylative arylations of amino acids, diastereoselective preparations of cis-cyclobutanes via [2 + 2] cycloadditions of enones, selective reductions of benzylic and α-carbonyl halides and, with fac-Ir(ppy)3, reductions of unactivated alkyl iodides [5][6][7][8]. Furthermore, the value of

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

• Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

• , enantioselective tandem conjugate addition–aldol reaction of cyclic enones [19]. While tandem conjugate addition–α-functionalization reactions were well known prior to Feringa’s publication [20] (Scheme 1), this work was unique because of the high enantioselectivity that was observed through the use of a chiral

Natural phenolic metabolites with anti-angiogenic properties – a review from the chemical point of view

• Qiu Sun,
• Jörg Heilmann and
• Burkhard König

Beilstein J. Org. Chem. 2015, 11, 249–264, doi:10.3762/bjoc.11.28

• superior inhibition to that of the natural parent product. This work was followed by more comprehensive bioactive studies on aromatic enones utilizing the substituted chalcone backbone [26]. The study showed that the presence of the enone moiety played an important role in maintaining the activity in the

• than curcumin. To date, the number of synthesized single enones and MACs have surpassed the 1000 mark. Ellagic acid Ellagic acid (7) is a naturally existing phenolic antioxidant widely found in numerous fruits and vegetables, such as raspberries (Rubus idaeus L., Rosaceae), strawberries (Fragaria spec

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• observed due, apparently, to the addition of the C-radical generated from ketone to benzene [204]. It was shown [209] that the α’-acetoxylation of enones occurs with good selectivity in other solvents, such as cyclohexane and acetonitrile, as well. The acyloxylation of enones and aryl ketones 220 with

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• binaphthyl skeleton, Fu and co-workers developed the first asymmetric [3 + 2] annulation of ethyl allenoate with various α,β-unsaturated enones to provide functionalized cyclopentenes (Scheme 2) [35]. The key structural feature of the chiral catalyst B1 is its rigid binaphthyl skeleton. This approach allowed

• synthesized a series of ferrocene-modified planar chiral phosphines featuring a new skeleton (Figure 3) [44][45]. Among these compounds, the P-cyclohexyl phosphine C1 proved to be the most efficient catalyst for [3 + 2] cycloadditions of ethyl 2,3-butadienoate with activated enones, fumarate esters, and

• various aspartic acid derivatives. Using the commercially available chiral catalyst (S,S)-Et-Duphos E7, Loh and co-workers developed the asymmetric [3 + 2] annulations of phenyl allenone and furanyl allenone with electron-deficient olefins, namely enones, maleates, and fumarates, to give corresponding

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• high level of stereocontrol (Scheme 4) [37][38][39][40]. Thus, vicinal and quartenary carbon centers can be obtained in high diasteromeric purity by conjugate additions of allyl, crotyl, and cinnamyl-derived anions to Michael acceptors such as enones, lactones, lactams, and α,β-unsaturated esters

• ][40]. Asymmetric conjugate additions using P-chiral phosphonamides were reported by Denmark [2][3][4] and Hua [5][6], with remarkable differences in selectivity depending on the configuration of the P-stereogenic center (Scheme 5). Thus, the addition of the Li-anion of trans-40a to cyclic enones 41

• in 28–64% ee [5]. In a similar fashion, Denmark’s oxazaphosphorinane cis-44a yielded keto esters 46a–c in high optical purities via conjugate addition to enones 41 followed by ozonolysis and oxidative esterification. Using diastereomer trans-44b on the other hand provided ketoesters 46a–c with only

Synthesis of a sucrose dimer with enone tether; a study on its functionalization

• Zbigniew Pakulski,
• Norbert Gajda,
• Magdalena Jawiczuk,
• Jadwiga Frelek,
• Piotr Cmoch and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2014, 10, 1246–1254, doi:10.3762/bjoc.10.124

• ). Functionalization of the three-carbon atom unit connecting the C5-positions of both sucrose units required reduction of the carbonyl group of the enone system and oxidation of the double bond. We have already reported that reduction of higher carbon sugar enones of the D series with zinc borohydride is highly

Preparation of phosphines through C–P bond formation

• Iris Wauters,
• Wouter Debrouwer and
• Christian V. Stevens

Beilstein J. Org. Chem. 2014, 10, 1064–1096, doi:10.3762/bjoc.10.106

• transfer yields the phosphine product 51 [124][125]. A chiral Pincer-palladium complex 55 has been used for the addition of diarylphosphines 25c to enones 53 (Table 4) [126]. Several enones 53, having electron-donating or -withdrawing groups on the aromatic ring, reacted with a variety of electron-rich and

Visible-light-induced, Ir-catalyzed reactions of N-methyl-N-((trimethylsilyl)methyl)aniline with cyclic α,β-unsaturated carbonyl compounds

• Dominik Lenhart and
• Thorsten Bach

Beilstein J. Org. Chem. 2014, 10, 890–896, doi:10.3762/bjoc.10.86

• used for the formation of carbon–carbon bonds [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. In non-silylated tertiary amines, a proton can act as a leaving group and photoinduced addition reactions of tertiary amines to enones are long known [23][24][25][26][27][28]. Mechanistically

• enones were made by Hoffmann et al., who established the use of aromatic ketones as suitable PET catalysts for these reactions [31][32][33][34][35][36][37]. In Scheme 1, the addition reaction of N,N-dimethylaniline (1) to (5R)-menthyloxyfuran-2(5H)-one (2) is shown, which proceeds to the intriguing

• -aminomethyl radicals [43][44][45] to enones. N-Methyl-N-((trimethylsilyl)methyl)aniline (5) for example served as substrate for the alkylation of 2-cyclohexenone (6) employing iridium catalyst 7. When using the amine as the limiting reagent and an excess of enone (1.5 equiv) product 8 was obtained in 70

Aza-Diels–Alder reaction between N-aryl-1-oxo-1H-isoindolium ions and tert-enamides: Steric effects on reaction outcome

• Amitabh Jha,
• Ting-Yi Chou,
• Zainab ALJaroudi,
• Bobby D. Ellis and
• T. Stanley Cameron

Beilstein J. Org. Chem. 2014, 10, 848–857, doi:10.3762/bjoc.10.81

• isoindolo[2,1-a]quinolone derivatives involves N-acyliminium ions or appropriate electron-deficient Schiff bases and subsequent [4 + 2] inverse-demand hetero-Diels–Alder cycloadditions with alkenes [11][12][13][14][15][16][17]. Vinylic systems from isoeugenol [11], cyclopentadiene [12], enones [13], vinyl

Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones

• Murat Kucukdisli,
• Dorota Ferenc,
• Marcel Heinz,
• Christine Wiebe and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 466–470, doi:10.3762/bjoc.10.44

• .10.44 Abstract The cyclocondensation of enones with aminoacetonitrile furnishes 3,4-dihydro-2H-pyrrole-2-carbonitriles which can be readily converted to 2,4-disubstituted pyrroles by microwave-induced dehydrocyanation. Alternatively, oxidation of the intermediates produces 3,5-disubstituted pyrrole-2

• the literature. They can be obtained from enones by Michael addition of nitromethane, partial reduction and dehydrogenation of the resulting pyrroline with selenium or sulfur in moderate yields (3 steps) [40][41]. Alternatively, a Nef reaction of the nitromethane adducts gives masked 1,4-dicarbonyls

• which can be cyclized to compounds 7 in yields of up to 50% (over 4 steps) [42]. Other methods involve the use of stoichiometric zirconocene dichloride [43], the reductive coupling of alkynes to enones followed by ozonolysis and Paal–Knorr cyclization [21] or the reaction of vinylazides with aldehydes

Additive-assisted regioselective 1,3-dipolar cycloaddition of azomethine ylides with benzylideneacetone

• Chuqin Peng,
• Jiwei Ren,
• Jun-An Xiao,
• Honggang Zhang,
• Hua Yang and
• Yiming Luo

Beilstein J. Org. Chem. 2014, 10, 352–360, doi:10.3762/bjoc.10.33

• with various dipolarophiles, such as α,β-unsaturated esters [21][22][23][24][25], dienones [26][27], α,β-unsaturated ketones [28][29][30], unsaturated aryl ketones [31][32][33] and electron-poor alkenes [34][35][36][37][38][39]. Among the studied α,β-unsaturated enones for 1,3-dipolar cycloaddition

• -unsaturated enones. Moreover, we envisioned that the additive might effectively tune the regioselectivity of a 1,3-dipolar cycloaddition of azomethine ylide. Herein, we report a three-component 1,3-dipolar cycloaddition of azomethine ylides, generated in situ from isatin derivatives and benzylamine, with

• nature of the substituent and its position on the benzylideneacetone aromatic ring significantly influenced the regioisomeric ratio. In general, the regioisomeric ratio with water as an additive is comparatively higher for the substrates in which the phenyl rings of enones were substituted by electron

Synthesis of the B-seco limonoid core scaffold

• Hanna Bruss,
• Hannah Schuster,
• Rémi Martinez,
• Markus Kaiser,
• Andrey P. Antonchick and
• Herbert Waldmann

Beilstein J. Org. Chem. 2014, 10, 194–208, doi:10.3762/bjoc.10.15

• Buchwald’s procedure for the catalytic asymmetric vinylation of enones [51]. However, the desired vinylated product could not be obtained under the described conditions. An alternative α-formylation/Wittig olefination sequence gave only low yields. O’Brien et al. [41] described the failure of a direct

Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

• Verena Weidmann,
• Mathias Schaffrath,
• Holger Zorn,
• Julia Rehbein and
• Wolfgang Maison

Beilstein J. Org. Chem. 2013, 9, 2233–2241, doi:10.3762/bjoc.9.262

• Chemistry and Food Biotechnology, Heinrich-Buff-Ring 58, 35392 Gießen Department of Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany 10.3762/bjoc.9.262 Abstract Allylic oxidations of olefins to enones allow the efficient synthesis of value-added products from simple

• Pleurotus sapidus. This ‘’mushroom catalysis’’ is operationally simple and allows the conversion of various unsaturated spirocyclic terpenoids. A number of new spirocyclic enones have thus been obtained with good regio- and chemoselectivity and chiral separation protocols for enantiomeric mixtures have been

• developed. The oxidations follow a radical mechanism and the regioselectivity of the reaction is mainly determined by bond-dissociation energies of the available allylic CH-bonds and steric accessibility of the oxidation site. Keywords: allylic oxidation; CH-activation; chiral separation; enones; flavors

Regioselective 1,4-trifluoromethylation of α,β-unsaturated ketones via a S-(trifluoromethyl)diphenylsulfonium salts/copper system

• Satoshi Okusu,
• Yutaka Sugita,
• Etsuko Tokunaga and
• Norio Shibata

Beilstein J. Org. Chem. 2013, 9, 2189–2193, doi:10.3762/bjoc.9.257

• ketones by the use of shelf-stable electrophilic trifluoromethylating reagents, S-(trifluoromethyl)diphenylsulfonium salts and copper under mild conditions is described. A wide range of acyclic aryl–aryl–enones and aryl–alkyl–enones were converted into β-trifluoromethylated ketones in low to moderate

• of regioisomers (C2/C3 1.1:1) [22]. We disclose herein the regioselective 1,4-addition of the CF3 group into simple conjugated acyclic enones including chalcones using S-(trifluoromethyl)diphenylsulfonium salt 3 and a copper system in 11–37% yields (12 examples). Results and Discussion We initiated

Synthesis of enones, pyrazolines and pyrrolines with gem-difluoroalkyl side chains

• Assaad Nasr El Dine,
• Ali Khalaf,
• Danielle Grée,
• Olivier Tasseau,
• Fares Fares,
• Nada Jaber,
• Philippe Lesot,
• Ali Hachem and
• René Grée

Beilstein J. Org. Chem. 2013, 9, 1943–1948, doi:10.3762/bjoc.9.230

• -mediated isomerisation affords enones in fair yields with a gem-difluoroalkyl chain. These derivatives were used to prepare pyrazolines and pyrrolines with the desired gem-difluoroalkyl side chain by cyclocondensations in good yields and with excellent stereoselectivity. A one-pot process was also

• ][21][22]. The goal of the present work is to demonstrate that selected propargylic derivatives [23][24][25] can be employed for the preparation of enones with a gem-difluoroalkyl chain by using an isomerisation process (Scheme 1). These intermediates can be employed for the preparation of

• bearing a CF3 group on the triple bond could be isomerised to the corresponding enones. In that case, Et3N proved to be sufficient as a catalyst to perform this transformation [28]. The required starting propargylic alcohols were obtained by a reaction of the lithium salt of easily available gem-difluoro

Gold-catalyzed regioselective oxidation of propargylic carboxylates: a reliable access to α-carboxy-α,β-unsaturated ketones/aldehydes

• Kegong Ji,
• Jonathan Nelson and
• Liming Zhang

Beilstein J. Org. Chem. 2013, 9, 1925–1930, doi:10.3762/bjoc.9.227

• following observations and considerations: a) propargylic carboxylates of type 4a with an internal C–C triple bond typically undergo facile 3,3-rearrangements [26][27][28][29][30] instead of 1,2-acyloxy migrations. The former process would eventually lead to the formation of the enones 6 [31]. Due to