Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• sodium sulfinates and enamides, applying Rose Bengal as photocatalyst and nitrobenzene as terminal oxidant (Scheme 43) [80]. In general, this procedure is suitable for the cross-coupling of a variety of substituted secondary enamides with alkyl, aryl and heteroaryl sodium sulfinate salts. Tertiary

• enamides could not be reacted with sodium sulfinates to yield the respective products. Wang and co-workers described a new method for the cyclization of phenyl propiolates with sulfinic acids, generating valuable coumarin derivatives in 2015 (Scheme 44) [81]. Visible-light irradiation of Eosin Y allows the

• ]. Two examples, norbonene and styrene, were presented and [Ru(bpy)3]Cl2 was used as photoredox catalyst. The groups of Zhang and Yu reported two additional photoredox-catalyzed methods for the sulfonylation of olefins. In their first paper they applied enamides as olefins, which were sulfonylated to the

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• reaction, in classical solvents or in an ionic liquid media, to yield the corresponding CF3 alkenes (Scheme 28) [35][36]. As for Yu, Zhang and co-workers, they described the trifluoromethylation of two enamides under photocatalytic conditions, using similar conditions as those they proposed for the

• trifluoromethylation of (hetero)arenes under photoredox catalysis. Direct C–H trifluoromethylation of five- and six-membered ring (hetero)arenes using heterogeneous catalysis. Trifluoromethylation of terminal olefins. Trifluoromethylation of enamides. (E)-Selective trifluoromethylation of β-nitroalkenes under

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• that use SelectfluorTM (8) as a simple and highly reactive electrophilic F-transfer reagent. Besides fluoro-cyclizations of olefines [56], also the asymmetric α-fluorination of prochiral carbonyl compounds or analogues like enamides 7 has been carried out with remarkable enantioselectivities by using

Synergistic chiral iminium and palladium catalysis: Highly regio- and enantioselective [3 + 2] annulation reaction of 2-vinylcyclopropanes with enals

• Haipan Zhu,
• Peile Du,
• Jianjun Li,
• Ziyang Liao,
• Guohua Liu,
• Hao Li and
• Wei Wang

Beilstein J. Org. Chem. 2016, 12, 1340–1347, doi:10.3762/bjoc.12.127

• the reaction with highly active dipolarophiles, such as electrophilic C=O [35], e.g., aldehydes [36][37][38], ketones [38][39], and imines [40], and nucleophilic enol ethers [38][41], enamides [42], and indoles [43]. Nonetheless, the reactions with the α,β-unsaturated aldehydes and ketones face

Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides – scope and limitations

• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1170–1177, doi:10.3762/bjoc.12.112

• formed. Instead, we isolated the trisubstituted oxazole derivative 6 in 55% yield. The scope of this reaction has not been studied by us, however it is known in the literature that enamides can undergo related oxidative cyclizations to oxazoles in the presence of the reagent cocktail employed or under

Studies on the synthesis of peptides containing dehydrovaline and dehydroisoleucine based on copper-mediated enamide formation

• Franziska Gille and
• Andreas Kirschning

Beilstein J. Org. Chem. 2016, 12, 564–570, doi:10.3762/bjoc.12.55

• conjugated alkene. Principally, enamides can also be prepared by the copper-mediated C–N coupling between a vinyl halide 6 and an amide 5 as reported by Ogawa and co-workers in 1991 [6]. Later, the group of Porco showed that copper(I) thiophencarboxylate is a suitable catalyst to promote this reaction in the

Hydrogenation of unactivated enamines to tertiary amines: rhodium complexes of fluorinated phosphines give marked improvements in catalytic activity

• Sergey Tin,
• Tamara Fanjul and
• Matthew L. Clarke

Beilstein J. Org. Chem. 2015, 11, 622–627, doi:10.3762/bjoc.11.70

• method to produce tertiary amines is by the hydrogenation of enamines. While the hydrogenations of enamides, bearing coordinating acyl substituents is probably the most developed and studied of all hydrogenation processes, studies on the hydrogenation of unactivated enamines are scarce and several

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

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

• and Diels–Alder cascade. Concomitant electrophilic aromatic substitution and dehydration resulted in isoquinoloquinoline derivatives [22]. Similarly, isoindoloquinolines were also synthesized via classical Povarov chemistry between furyl aldimines and tert-enamides followed by a N-acryloylation, Diels

• (series 1 and 2) from 1-oxo-2-aryl-1H-isoindolium ions (A) and appropriate tert-enamides (Scheme 1). Although this is the first report of the use of tert-enamides as a dienophile for the hetero-Diels–Alder reaction with N-acyliminium cations, formation of isoindoloquinolines (series 1 and 2) was rather

• expected based on literature reports [11][12][13][14][15][16][17]. The unpredicted formation of E-2-(2-substituted-aryl)-3-(2-(2-oxopyrrolidin-1-yl)vinyl)isoindolin-1-ones (series 3, Figure 1) from N-(2-substituted-aryl)-1-oxo-1H-isoindolium ions (A) and tert-enamides under identical conditions forms the

The Flögel-three-component reaction with dicarboxylic acids – an approach to bis(β-alkoxy-β-ketoenamides) for the synthesis of complex pyridine and pyrimidine derivatives

• Mrinal K. Bera,
• Moisés Domínguez,
• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 394–404, doi:10.3762/bjoc.10.37

• these enamides to 4-hydroxypyridine derivatives or to functionalized pyrimidines efficiently provided symmetrically and unsymmetrically substituted fairly complex (hetero)aromatic compounds containing up to six conjugated aryl and hetaryl groups. In addition, subsequent functionalizations of the

• E- and Z-configured enamide moieties [51][52], finally leading to identical products. After these successful multicomponent reactions we investigated the intramolecular condensations of the bis(β-ketoenamides) 13–15 to pyridine and pyrimidine derivatives. Enamides 13 and 14 were treated with

Regio- and stereoselective carbometallation reactions of N-alkynylamides and sulfonamides

• Yury Minko,
• Morgane Pasco,
• Helena Chechik and
• Ilan Marek

Beilstein J. Org. Chem. 2013, 9, 526–532, doi:10.3762/bjoc.9.57

• : carbometallation; enamides; organocopper; regiochemistry; ynamides; Introduction Due to a strong differentiation of electron density on the two sp-hybridized carbon atoms, N-alkynylamides (ynamides) have become attractive substrates involved in many synthetically useful transformations [1][2][3][4]. The

• ynamides to be of easy access to the whole synthetic community [8][9][10][11][12][13][14]. Similarly, enamides are another important class of substrates involved in numerous applications in organic synthesis [5][15]. As one of the most straightforward and well-developed methods to generate polysubstituted

• a α/β ratio of 18:82. When N-alkynylamide 4 was treated under our copper-catalyzed carbomagnesiation conditions (conditions B), enamides 6 were similarly obtained as a pure α-isomer. Although this transformation requires higher temperature, yields are usually better than in reactions with the

Facile synthesis of functionalized tetrahydroquinolines via domino Povarov reactions of arylamines, methyl propiolate and aromatic aldehydes

• Jing Sun,
• Hong Gao,
• Qun Wu and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2012, 8, 1839–1843, doi:10.3762/bjoc.8.211

• dienophiles, vinyl enol ethers, vinyl enamides, vinyl sulfides, cyclopentadienes, indenes, alkynes and enamines have been mostly used in this method [12][13][14][15][16][17][18][19][20][21][22]. β-Enamino esters [23][24][25][26], which may be readily generated in situ by the addition of a primary amine to

• ]. However, a survey of literature reveals that a Povarov reaction with in situ generated β-enamino ester as dienophile has not been reported until now. Recently, Zhu and Masson successfully developed three-component Povarov reactions using enamides as dienophiles leading to a highly efficient synthesis of

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• Figure 2 [60]. General base catalysis appeared also to be essential for iminium activated reactions of α,β-unsaturated aldehydes with enamides 17. By studying the kinetics of the reactions of enamides 17 with benzhydrylium ions 18 (Figure 11) we determined the reactivity parameters N and sN for these π

• -nucleophiles, which are listed in Figure 12 [61]. Figure 12 shows that the nucleophilicities N of the enamides 17 are comparable to those of silylated enol ethers, in between those of allylsilanes and enamines. Accordingly, we expected them to react readily with the iminium ions 3 at room temperature. However

• , when the iminium triflates or hexafluorophosphates 3a and 3b (~ 5 × 10–5 M) were combined with 25 equivalents of the enamides 17b and 17g in CH2Cl2 or CH3CN, no consumption of the iminium ions was observed [61]. These reactions took place in the presence of 2,6-lutidine, however, indicating the need of

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• obtained in all cases. A similar Markovnikov hydroamination [59] could also be achieved via an intermolecular hydroamination of allenamides 123 with arylamines under mild AuPPh3OTf catalysis conditions to furnish allylamino (E)-enamides stereoselectively (Scheme 22). Hesp and co-workers have identified a

• and mild synthesis of enamides (193–196) by a gold-catalyzed nucleophilic addition to allenamides 191 (Scheme 36) [87]. For example, treatment of allenamide and 1-methylindole with 5.0 mol % of PPh3AuNTf2 in CH2Cl2 at room temperature gave the corresponding enamide in 83% yield. Gold-catalyzed direct

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• mechanism involves the reaction of the olefin with the ipso position of the aromatic ring affording a spiro biradical intermediate. Recombination of these radicals proceeds further until formation of the final compound. Some years later, Kohmoto showed that similar enamides linked to a naphthyl moiety

An efficient and practical entry to 2-amido-dienes and 3-amido-trienes from allenamides through stereoselective 1,3-hydrogen shifts

• Ryuji Hayashi,
• John B. Feltenberger,
• Andrew G. Lohse,
• Mary C. Walton and
• Richard P. Hsung

Beilstein J. Org. Chem. 2011, 7, 410–420, doi:10.3762/bjoc.7.53

• ][41][42][43], for earlier studies on allenamides see [44][45][46]) can open the door to construct synthetically useful amido-dienes (for a review on the synthesis of enamides see [47], for reviews on the chemistry of dienamides see [48][49][50], for reviews on the chemistry of 2-amino or 2-amido

Recent advances in carbocupration of α-heterosubstituted alkynes

• Ahmad Basheer and
• Ilan Marek

Beilstein J. Org. Chem. 2010, 6, No. 77, doi:10.3762/bjoc.6.77

• change the stereochemical outcome of the reaction. Representative examples are given in this mini-review. Keywords: alkynes; carbocupration; enamides; regioselectivity; stereoselectivity; syn-addition; vinylcopper; ynamides; ynol ether; Review The addition of a carbon-metal bond of an organometallic

A divergent asymmetric approach to aza-spiropyran derivative and (1S,8aR)-1-hydroxyindolizidine

• Jian-Feng Zheng,
• Wen Chen,
• Su-Yu Huang,
• Jian-Liang Ye and
• Pei-Qiang Huang

Beilstein J. Org. Chem. 2007, 3, No. 41, doi:10.1186/1860-5397-3-41

• to N,O-dibenzyl malimide (4) leads to N,O-acetals 5 in high regioselectivity (Scheme 2), and the subsequent reductive dehydroxylation gives 6 in high trans-diastereoselectivity.[35] On the other hand, treatment of N,O-acteals 5 with an acid furnished enamides E, which can be transformed

• -hydroxyindolizidine skeleton (ent-3) can be constructed in a concise and selective manner. It is worthy of mention that in addition to the reductive dehydroxylation leading to 2-pyrrolidinones 6, and the acid-promoted dehydration leading to (E)-enamides E (and then F, G), acid treatment of the N,O-acetal 5a could