Rhodium, iridium and nickel complexes with a 1,3,5-triphenylbenzene tris-MIC ligand. Study of the electronic properties and catalytic activities

• Carmen Mejuto,
• Beatriz Royo,
• Gregorio Guisado-Barrios and
• Eduardo Peris

Beilstein J. Org. Chem. 2015, 11, 2584–2590, doi:10.3762/bjoc.11.278

• addition reaction of arylboronic acids to α,β-unsaturated ketones. Keywords: arylation of unsaturated ketones; mesoionic carbenes; nickel; iridium; rhodium; Introduction Highly symmetrical poly-NHCs are a very interesting type of ligands, because they allow the preparation of a variety of supramolecular

• the catalytic properties of the tris-NHC Rh(I) complex 6 (Scheme 4) in the rhodium-catalyzed addition of arylboronic acids to α,β-unsaturated ketones [25] we decided to study complex 2 in the same reaction. From these comparative data it was assumed to gaining more information about the effects of the

• nature of the carbene ligand while maintaining a similar structural environment on the catalyst. The catalytic addition of arylboronic acids to α,β-unsaturated ketones [58][59][60][61][62] is a process for which several Rh(I)-NHC complexes have afforded excellent activities and chemoselectivities [58][63

Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

• Takamichi Wakamatsu,
• Kazunori Nagao,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2015, 11, 2444–2450, doi:10.3762/bjoc.11.265

• not been used for these methods [11]. As related studies we reported earlier the copper-catalyzed conjugate addition of alkylboranes (alkyl-9-BBN) to imidazole-2-yl α,β-unsaturated ketones [12][13][14] and the copper-catalyzed three-component coupling with alkylboranes, alkynoates, and tributyltin

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

• performance in terms of enantioselectivity, and was used in combination with Cu(OTf)2 in the 1,6-ACA of cyclic dienones of the type 30 (Scheme 6). NHC ligands also enabled a total regioselectivity and ees ranging from 58 to 91%. Given the efficiency of (R)-Binap L4 in Cu-catalyzed 1,4-ACA on α,β-unsaturated

• ketones [21], the potency of other atropoisomeric diphosphines was also studied in 1,4 and 1,6-conjugate additions with cyclic and linear substrates [27]. (S)-Synphos L6 and (R)-Fluorophos L7 were used in combination with CuTC and compared to L4 (Scheme 7). Notably, the reaction of cyclic dienone 32 with

Intermolecular addition reactions of N-alkyl-N-chlorosulfonamides to unsaturated compounds

• Gerold Heuger and
• Richard Göttlich

Beilstein J. Org. Chem. 2015, 11, 1226–1234, doi:10.3762/bjoc.11.136

• aminohalogenation of cinnamic esters using N,N-dichloro-p-toluenesulfonamide and ZnCl2 or Cu(OTf)2 [18] as catalysts and transferred these conditions to reactions with alkynes [19][20][21] and α,β-unsaturated ketones [19][20][21]. An ionic mechanism via halonium ions was proposed. The amidofluorination of alkenes

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

• expanded to include α,β-unsaturated ketones, aldehydes, lactones, esters, nitroolefins, and to a lesser extent α,β-unsaturated amides and lactams. Review The lack of development in the CA of α,β-unsaturated amides and lactams is not surprising because these substrates are significantly less reactive than

• α,β-unsaturated amides and lactams are less reactive, the ACA reactions that have been developed for α,β-unsaturated ketones, esters and other substrates, would not necessarily work well on α,β-unsaturated amides and lactams. Therefore, the focus of this review is to highlight the work that has been

• pyrrolinones have only resulted in low yields and enantioselectivities. Compared to the number of existing methods for copper-catalyzed ECA reactions of α,β-unsaturated ketones and other substrates, there is definitely a need for additional research in this area. 2.2 Rhodium-catalyzed ECA reactions Unlike

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

• system; different β-keto esters and hydroxamic acid derivatives can be used [203]. The acetoxylation at the α’-position of α,β-unsaturated ketones with Mn(OAc)3 was studied in detail. It is suggested that manganese(III) acetate causes the generation of C-radicals from ketones followed by the

• ) were obtained in 61–85% yield [211]. This method was modified by using not carboxylic acids but their mixtures with the corresponding anhydrides and was applied to the α’-acyloxylation of α,β-unsaturated ketones with complex structures with the aim of preparing analogues of natural compounds [212]. 4

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

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

• diphenylphosphine to α,β-unsaturated ketones [127][128], esters [129], sulfonic esters [130] or to dienones [131]. The proposed mechanism is ubiquitous in metal-catalyzed hydrophosphination involving a P–H oxidative addition, insertion of the olefin into the Pd–H bond and reductive elimination. In 2007 several

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

• and delivered product 14 in 41% yield. Addition to cyclic α,β-unsaturated ketones Based on the results obtained with five-membered lactone 9, it was suprising to note that the related five-membered enone, 2-cyclopentenone (15), delivered mainly the direct addition product 17 instead of the tricyclic

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

• detailed mechanism is still underway and will be published in due course. Having established the optimal protocol for this reaction, we next examined the scope of this method with regard to α,β-unsaturated ketones and azomethine ylides. With the aim of applying this additive-assisted regioselective 1,3

Organobase-catalyzed three-component reactions for the synthesis of 4H-2-aminopyrans, condensed pyrans and polysubstituted benzenes

• Moustafa Sherief Moustafa,
• Saleh Mohammed Al-Mousawi,
• Maghraby Ali Selim,
• Ahmed Mohamed Mosallam and
• Mohamed Hilmy Elnagdi

Beilstein J. Org. Chem. 2014, 10, 141–149, doi:10.3762/bjoc.10.11

• methylenenitriles to α,β-unsaturated ketones [8], 2-amino-4H-pyrans 1 (Scheme 1) have become the central focus of a number of chemical and biological investigations [9][10]. Perez et al. recently reported an interesting method for the synthesis of condensed pyridines 2 through a three-component reaction of

• 37b. X-ray crystal structure of 39. Reaction of active methylenenitriles with α,β-unsaturated ketones 1. Synthesis of 2-amino-4-phenyl-3-cyanopyridines 2. Synthesis of polysubstituted benzenes 3. Syntheses of compound 9 and compounds 13a,b. Syntheses of compounds 18 and 21. Syntheses of compound 26

The regioselective synthesis of spirooxindolo pyrrolidines and pyrrolizidines via three-component reactions of acrylamides and aroylacrylic acids with isatins and α-amino acids

• Tatyana L. Pavlovskaya,
• Fedor G. Yaremenko,
• Victoria V. Lipson,
• Svetlana V. Shishkina,
• Oleg V. Shishkin,
• Vladimir I. Musatov and
• Alexander S. Karpenko

Beilstein J. Org. Chem. 2014, 10, 117–126, doi:10.3762/bjoc.10.8

• nonnatural α-amino acids [11][12][13], more than fifteen isatins [14], and 1,3-dipolarophiles, e.g. α,β-unsaturated ketones [15][16][17], maleimides [18][19], benzo[b]thiophene-1,1-dioxide [20], bis(arylmethylidene)acetones and -cycloalkanones [21][22], 1,4-naphthoquinone [23], arylidenemalonodinitriles [24

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• provides an efficient tool for introducing the hydroperoxide function. The reaction starts with the coordination of oxygen to the double bond followed by the formation of hydroperoxides presumably by a stepwise or concerted mechanism [229][230]. The oxidation of α,β-unsaturated ketones 1a–c by singlet

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

• aluminium-centered Lewis acid with low to moderate yields [18]. Dilman and co-workers partially overcame this problem by using highly electrophilic alkenes bearing either Meldrum’ acids [19], or two geminal nitrile groups [20]. However, direct 1,4-trifluoromethylation to conventional α,β-unsaturated ketones

•  1, entry 17). With suitable conditions in hand, the scope of copper-mediated conjugate trifluoromethylation of α,β-unsaturated ketones 1 with 3a was explored with a variety of substrates selected in order to establish the generality of the process (Table 2). With respect to the aryl ketone group

• -substituted enone also produced the desired product 2l (Table 2, entry 12). Based on these results, we hypothesized the reaction mechanism as shown in Scheme 2. First, the conjugate trifluoromethylation of α,β-unsaturated ketones would be initiated by a single-electron transfer between S-(trifluoromethyl

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

• the use of a P,S-bidentate ligand, which is proposed to enable the formation of tris-coordinated and hence less electrophilic gold carbene species. α-Carboxy α,β-unsaturated ketones/aldehydes can be obtained with fair to excellent yields. Keywords: enone; gold catalysis; oxidation; propargyl

• the tertiary counterpart underwent gold-catalyzed 3,3-rearrangement preferentially [21] and hence was not a viable substrate. Except entry 7, the gold-catalyzed oxidations proceeded with excellent regioselectivities (>25:1), and the desired α-acyloxy α,β-unsaturated ketones/aldehyde were isolated with

• scope is much limited, and the catalyst loading is 20%. With this oxidative gold catalysis, the propargyl esters, except those derived from tertiary alcohols, can be reliably converted into α-acyloxy α,β-unsaturated ketones/aldehydes. Conclusion We have realized a gold-catalyzed, highly regioselective

Establishing the concept of aza-[3 + 3] annulations using enones as a key expansion of this unified strategy in alkaloid synthesis

• Aleksey I. Gerasyuto,
• Zhi-Xiong Ma,
• Grant S. Buchanan and
• Richard P. Hsung

Beilstein J. Org. Chem. 2013, 9, 1170–1178, doi:10.3762/bjoc.9.131

• employ vinylogous amides tethered to α,β-unsaturated ketones, or enones 1b (R ≠ H) (Scheme 1). Conceptually, employing enals or enones in an aza-[3 + 3] annulation appears to constitute very little difference, with the major difference lying in the R group in their respective products 3 and 4. While

Efficient synthesis of β’-amino-α,β-unsaturated ketones

• Isabelle Abrunhosa-Thomas,
• Aurélie Plas,
• Nishanth Kandepedu,
• Pierre Chalard and
• Yves Troin

Beilstein J. Org. Chem. 2013, 9, 486–495, doi:10.3762/bjoc.9.52

• –Emmons reaction as a key step for generating the β'-amino-α,β-enones, permits access to a range of substrates under mild conditions and in moderate to high yield. Keywords: β’-amino-α,β-unsaturated ketones; Horner–Wadsworth–Emmons reaction; stereoselective synthesis; Introduction Compounds

• preparation of chiral 2,6-disubstituted piperidines, we wish to report here a facile synthetic route to various β’-carbamate-α,β-unsaturated ketones in good overall yields and good enantioselectivities. Results and Discussion In a preliminary approach, preparation of β-amino ketones was envisaged through a

• did not allow the use of a wide range of functional groups and sometimes gave bad overall yields, we devised a general and simple method to easily access a variety of β’-amino-α,β-unsaturated ketones by a more convenient route using the Horner–Wadsworth–Emmons reaction [19][20] as the key step, as

Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions

• Matthias Leven,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2013, 9, 155–165, doi:10.3762/bjoc.9.18

• -hydroxycoumarin (1) to prochiral α,β-unsaturated ketones. Instead of acid additives, which sometimes lead to decomposition of sensitive components [18], alkali-metal ions are employed as very mild Lewis acids (Scheme 1). The activation of Michael acceptors by iminium ions enables asymmetric additions of 4

• -hydroxycoumarins to α,β-unsaturated ketones (Scheme 2) [19][20][21][22][23][24][25][26][27]. There is a wide spread of 4-hydroxycoumarins in pharmaceuticals such as anticoagulants and substances that inhibit HIV or malaria [28][29]. Among the most prominent chiral 4-hydroxycoumarins is warfarin, which works as a

• , which are able to form imine complexes with prochiral α,β-unsaturated ketones, which could be detected by ESIMS spectrometry in an exemplary case. It was found that the Lewis acidities of the alkali metal ions are strong enough to activate the imine homologous Michael systems for nucleophilic addition

Features of the behavior of 4-amino-5-carboxamido-1,2,3-triazole in multicomponent heterocyclizations with carbonyl compounds

• Eugene S. Gladkov,
• Katerina A. Gura,
• Svetlana M. Sirko,
• Sergey M. Desenko,
• Ulrich Groth and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2012, 8, 2100–2105, doi:10.3762/bjoc.8.236

• or thermal heating was substituted by ultrasonication at ambient temperature or when the three-component reaction was replaced by a sequential protocol via the preliminary synthesis of cyclic α,β-unsaturated ketones. Some MCRs of aminoazoles with controlled switching of the direction. Some possible

Organocatalytic cascade aza-Michael/hemiacetal reaction between disubstituted hydrazines and α,β-unsaturated aldehydes: Highly diastereo- and enantioselective synthesis of pyrazolidine derivatives

• Zhi-Cong Geng,
• Jian Chen,
• Ning Li,
• Xiao-Fei Huang,
• Yong Zhang,
• Ya-Wen Zhang and
• Xing-Wang Wang

Beilstein J. Org. Chem. 2012, 8, 1710–1720, doi:10.3762/bjoc.8.195

• -pyrazolines starting from α,β-unsaturated ketones and phenylhydrazine or N-tert-butyloxycarbonylhydrazine in the presence of a chiral Brønsted acid or a phase-transfer catalyst [70][71]. Compared with monosubstituted hydrazines in organocatalytic asymmetric synthesis, disubstituted hydrazines were also

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• (prolinamide or prolinol) leading to optically active 4-hydroxy-4H chromene-3-carbaldehydes 9 (Scheme 8). The reactions proceeded with good yields and enantiomeric ratio up to 98:2 by using the bulky catalyst prolinol diphenyl silylether Ia in dichloromethane/ethanol (1:1) at room temperature. Cyclic α,β

• -unsaturated ketones have also responded as Michael acceptors in the organocatalytic tandem Michael addition reaction towards the synthesis of tetrahydroxanthones. Córdova et al. [50], in 2007, reported the first organocatalytic asymmetric synthesis of tetrahydroxanthenones through the domino Michael–aldol

N-Heterocyclic carbene/Brønsted acid cooperative catalysis as a powerful tool in organic synthesis

• Rob De Vreese and
• Matthias D’hooghe

Beilstein J. Org. Chem. 2012, 8, 398–402, doi:10.3762/bjoc.8.43

• -unsaturated aldehydes [18], the enantioselective synthesis of cyclopentenes from α,β-unsaturated aldehydes and α,β-unsaturated ketones [19], and the preparation of cyclopentanes through the reaction of enals and β,γ-unsaturated α-ketoesters [20]. Discussion Recently, Rovis et al. reported that the acetate

Syntheses and applications of furanyl-functionalised 2,2’:6’,2’’-terpyridines

• Jérôme Husson and
• Michael Knorr

Beilstein J. Org. Chem. 2012, 8, 379–389, doi:10.3762/bjoc.8.41

• [14]. This strategy was also successfully applied to the preparation of some furanyl-substituted terpyridines. The synthetic sequence starts from furanyl aldehydes 1–3 and 2-acetylpyridine (4). The first step is a base-mediated aldol-condensation that yields the α,β unsaturated ketones 5–7. Reacting

Continuous-flow hydration–condensation reaction: Synthesis of α,β-unsaturated ketones from alkynes and aldehydes by using a heterogeneous solid acid catalyst

• Magnus Rueping,
• Teerawut Bootwicha,
• Hannah Baars and
• Erli Sugiono

Beilstein J. Org. Chem. 2011, 7, 1680–1687, doi:10.3762/bjoc.7.198

• of α,β-unsaturated ketones starting from alkynes and aldehydes by employing a heterogeneous catalyst in a flow microwave. The procedure presents a straightforward and convenient access to valuable differently substituted chalcones and can be applied on multigram scale. Keywords: chalcones; flow

• and microwave heating offers advantages such as a cleaner reaction profile, reduction of reaction times, higher yields and better selectivity [41][42][43][44][45][46][47][48][49][50][51][52][53][54]. Results and Discussion α,β-Unsaturated ketones are a common motif found in the principal core of a

• and other heterocyclic compounds [61][62][63][64][65]. Consequently, the development of an efficient synthesis to obtain these valuable compounds attracted our interest. Thus, we decided to develop an efficient continuous-flow synthesis of α,β-unsaturated ketones starting from alkynes and aldehydes by

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• pyrazoles in a consecutive fashion from terminal alkynes, acid chlorides, and hydrazine derivatives. Classical approaches to these valuable compounds are notably based on the cyclocondensation of hydrazine derivatives with 1,3-disubstituted three-carbon units, including α,β-unsaturated ketones, and

• ,β-unsaturated ketones generated in situ by Pd-catalyzed Sonogashira cross-coupling reactions. For instance, by building on their expertise in this area [14] Müller and coworkers recently developed a very effective and modular three-component strategy to assemble a series of 3,5-bis(hetero)aromatic

• addition of diethylphosphite. Moderate to good yields were obtained depending on the nature of the various components (Scheme 14) [13]. Amines as hetero-Michael donors Many multicomponent approaches to nitrogen heterocycles have been developed based on the reaction of nitrogen-centered nucleophiles with α