New syntheses of (±)-tashiromine and (±)-epitashiromine via enaminone intermediates

• Darren L. Riley,
• Joseph P. Michael and
• Charles B. de Koning

Beilstein J. Org. Chem. 2016, 12, 2609–2613, doi:10.3762/bjoc.12.256

• /C-8 bond. In this article we describe further extensions to our route to substituted indolizidines, and an application to the synthesis of racemic tashiromine (1) and epitashiromine (2). Results and Discussion One of the most versatile methods for preparing the enaminones of interest is the

• indolizidine skeleton. To this end we chose to investigate the reaction of 3-(2-thioxo-1-pyrrolidinyl)propyl acetate (3), which we had previously used as a precursor to enaminones and indolizidines [28], with three different reaction partners, namely, α-bromoacetone, ethyl α-bromoacetate and α

• -halocarbonyl compounds afforded enaminones 7a and 7b in good yields (90–95%), but the reaction with α-bromoacetonitrile gave enaminonitrile 7c in only 44% yield. The deacetylation of 7a–c with potassium carbonate in methanol afforded the corresponding alcohols 8a–c in good yields (82–89%; Table 1). The data

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