Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• [2,3,4-kl]acridines (the core structure of plakinidine C) from enaminones and 3-indolyl-3-hydroxyoxindoles through a cascade ring-opening/recyclization/methyl migration sequence (Scheme 61) [78]. The reactions proceeded well in MeCN in the presence of catalytic I2 (30 mol %) under an O2 atmosphere

• entry to polycyclic scaffolds for further biological screening. Similarly, Shi et al. established CPA-catalyzed highly enantioselective aza-ene reactions of cyclic enaminones with 3-indolyl-3-hydroxyoxindoles, incorporating enaminones and 3-indolyl-3-hydroxyoxindoles into C3-functionlized chiral indoles

An intramolecular C–N cross-coupling of β-enaminones: a simple and efficient way to precursors of some alkaloids of Galipea officinalis

• Hana Doušová,
• Radim Horák,
• Zdeňka Růžičková and
• Petr Šimůnek

Beilstein J. Org. Chem. 2015, 11, 884–892, doi:10.3762/bjoc.11.99

• catalytic hydrogenation of the corresponding quinolones 2 (Scheme 2) with yields not greater than 43%. In the present work, we introduce a quite different approach to the exocyclic enaminones 1 based on an intramolecular C–N cross-coupling of enaminones 3 (Scheme 2). Results and Discussion The synthesis of

• the starting substrates A simple retrosynthesis of enaminones 3 leads to the corresponding β-diketones 4 accessible through Claisen condensation of 3-phenylpropionic ester 5 with the appropriate acetophenone 6 (Scheme 3). The synthesis of ester 5 was accomplished according to Scheme 4. The classic

• ) indicates the presence of an intramolecular hydrogen bond N–H···O. The enaminones 3 therefore possess Z configuration on the C=C bond. The intramolecular C–N cross-coupling β-Enaminones and related polarized ethylenes (generally enamines substituted by EWG on β-carbon atom) belong among the rather neglected

A catalyst-free multicomponent domino sequence for the diastereoselective synthesis of (E)-3-[2-arylcarbonyl-3-(arylamino)allyl]chromen-4-ones

• Pitchaimani Prasanna,
• Pethaiah Gunasekaran,
• Subbu Perumal and
• J. Carlos Menéndez

Beilstein J. Org. Chem. 2014, 10, 459–465, doi:10.3762/bjoc.10.43

• structural fragment, since enaminones are versatile starting materials in organic synthesis and are notably important for the synthesis of nitrogen heterocycles [25][26][27]. In particular, β-enaminoketones are endowed with electrophilic and nucleophilic reaction centers and have a versatile reactivity that

• our starting enaminones, namely 2a (Ar = Ph) and 2c (Ar = 3-NO2C6H4) with aniline under our standard reaction conditions (DMF, 130 °C) affords the corresponding compounds 4 after 3 h in 94% and 90% yields, respectively. As previously mentioned (Table 1), the nature of the solvent was found to be of

Secondary amine-initiated three-component synthesis of 3,4-dihydropyrimidinones and thiones involving alkynes, aldehydes and thiourea/urea

• Jie-Ping Wan,
• Yunfang Lin,
• Kaikai Hu and
• Yunyun Liu

Beilstein J. Org. Chem. 2014, 10, 287–292, doi:10.3762/bjoc.10.25

• ] and enaminones [34]. On the other hand, as frequently utilized building blocks in organic synthesis, alkynes have been known to possess versatile reactivity in the synthesis of small molecules. For example, a previous protocol employing aryl alkynes, aldehydes and urea/thiourea has been found to

A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates

• František Josefík,
• Markéta Svobodová,
• Valerio Bertolasi and
• Petr Šimůnek

Beilstein J. Org. Chem. 2013, 9, 1463–1471, doi:10.3762/bjoc.9.166

• Diffratometrica, Università di Ferrara, Via L. Borsari 46, 441 00, Ferrara, Italy 10.3762/bjoc.9.166 Abstract Easily obtainable cyclic enaminones (piperidin-2-ylidenealkanones) can be transformed into substituted bicyclic pyridazinium tetrafluoroborates upon treatment with corresponding diazonium salts. The

• on this topic see, e.g. [1]), searching for new heterocyclic systems or novel methods for the synthesis of the existing ones represents a very important part of organic chemistry. Enaminones, due to their ability to react with both electrophiles and nucleophiles, are versatile synthons, and not only

• in heterocyclic chemistry (for many reviews see, e.g., [2][3][4][5][6]). During the past several years we have dealt with the reaction of various enaminones with diazonium salts and established a number of methods for the construction of some important or unusual heterocyclic systems [7][8][9][10][11

Synthesis of functionalized spiro[indoline-3,4’-pyridines] and spiro[indoline-3,4’-pyridinones] via one-pot four-component reactions

• Li-Juan Zhang,
• Qun Wu,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2013, 9, 846–851, doi:10.3762/bjoc.9.97

• arylamines and other primary amines. Keywords: 1,4-dihydropyridine; electron-deficient alkyne; four-component reaction; isatin; one-pot reaction; spiro compound; Introduction β-Enaminones and β-enamino esters represent important synthetic building blocks for the development of versatile carbon–carbon bond

Enaminones in a multicomponent synthesis of 4-aryldihydropyridines for potential applications in photoinduced intramolecular electron-transfer systems

• Nouria A. Al-Awadi,
• Maher R. Ibrahim,
• Mohamed H. Elnagdi,
• Elizabeth John and
• Yehia A. Ibrahim

Beilstein J. Org. Chem. 2012, 8, 441–447, doi:10.3762/bjoc.8.50

• Nouria A. Al-Awadi Maher R. Ibrahim Mohamed H. Elnagdi Elizabeth John Yehia A. Ibrahim Chemistry Department, Faculty of Science, Kuwait University, P.O. Box 5969, Safat 13060, Kuwait 10.3762/bjoc.8.50 Abstract An efficient three component reaction with enaminones, primary amines and aldehydes

• -naphthyl) and 4-(phenanthren-9-yl)dihydropyridine derivatives exhibited an interesting photoluminescence behavior, which suggests their potential application as suitable photoinduced intramolecular electron-transfer systems. Keywords: enaminones; 1,4-dihydropyridines; microwaves; multi-component reactions

• /aromatic amines, ethyl propiolate and benzaldehyde [14], or by a cascade reaction of 1-phenylpropynone or ethyl propiolate with primary amines and aldehyde [15]. Enaminones are versatile starting materials for the synthesis of many classes of organic compounds and heterocyclic systems [16][17], and are

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

Analogues of amphibian alkaloids: total synthesis of (5R,8S,8aS)-(−)-8-methyl- 5-pentyloctahydroindolizine (8-epi-indolizidine 209B) and [(1S,4R,9aS)-(−)-4-pentyloctahydro- 2H-quinolizin- 1-yl]methanol

• Joseph P. Michael,
• Claudia Accone,
• Charles B. de Koning and
• Christiaan W. van der Westhuyzen

Beilstein J. Org. Chem. 2008, 4, No. 5, doi:10.1186/1860-5397-4-5

• development of enaminones as versatile intermediates for the synthesis of alkaloids and other nitrogen-containing heterocycles. In this paper we describe the enantioselective synthesis of indolizidine and quinolizidine analogues of bicyclic amphibian alkaloids via pyrrolidinylidene- and piperidinylidene

• -containing enaminones. Results Our previously reported synthesis of racemic 8-epi-indolizidine 209B has been extended to the laevorotatory enantiomer, (−)-9. Attempts to adapt the synthetic route in order to obtain quinolizidine analogues revealed that a key piperidinylidene-containing enaminone intermediate

• quinolizidine 207I, 217A and related compounds have been reported [4][5][6][7][8][9]. As part of a long-standing investigation into the utility of pyrrolidinylidene- and piperidinylidene-containing enaminones (vinylogous urethanes) 5 and 6 as key intermediates in the synthesis of alkaloids and other nitrogen

2-Arylhydrazononitriles as building blocks in heterocyclic synthesis: A novel route to 2-substituted- 1,2,3-triazoles and 1,2,3-triazolo[4,5-b]pyridines

• Saleh M. Al-Mousawi and
• Moustafa Sh. Moustafa

Beilstein J. Org. Chem. 2007, 3, No. 12, doi:10.1186/1860-5397-3-12

• triazolopyridine 8, thus confirming that the aminofunction and the acetyl function are adjacent. Moreover, reacting 6 with dimethylformamide dimethylacetal (DMFDMA) afforded the cis enaminone 9 (J = 8 Hz) despite the fact that secondary enaminones have been established to prefer adopting the trans configuration

• as in 5 and therefore excluding 7 (Scheme 2). Typical of enaminones, compound 9 reacts with naphthoquinone to yield the benzofuran 12 and with hydrazine hydrate to yield pyrazolyl-1,2,3-triazole 13 in good yields. Attempts to convert 4 into oxadiazolylhydrazone 6 by heating in DMF afforded 14 whose