Synthesis of 3,4-dihydro-1,8-naphthyridin-2(1H)-ones via microwave-activated inverse electron-demand Diels–Alder reactions

• Salah Fadel,
• Youssef Hajbi,
• Mostafa Khouili,
• Said Lazar,
• Franck Suzenet and
• Gérald Guillaumet

Beilstein J. Org. Chem. 2014, 10, 282–286, doi:10.3762/bjoc.10.24

• electron-demand Diels–Alder reaction from 1,2,4-triazines bearing an acylamino group with a terminal alkyne side chain. Alkynes were first subjected to the Sonogashira cross-coupling reaction with aryl halides, the product of which then underwent an intramolecular inverse electron-demand Diels–Alder

Synthesis and biological activity of N-substituted-tetrahydro-γ-carbolines containing peptide residues

• Nadezhda V. Sokolova,
• Valentine G. Nenajdenko,
• Vladimir B. Sokolov,
• Daria V. Vinogradova,
• Elena F. Shevtsova,
• Ludmila G. Dubova and
• Sergey O. Bachurin

Beilstein J. Org. Chem. 2014, 10, 155–162, doi:10.3762/bjoc.10.13

• of mitochondria but possessed some inhibitory effect on the mitochondria permeability transition. The original N-substituted-tetrahydro-γ-carbolines containing an terminal alkyne group demonstrated a high prooxidant activity, whereas their conjugates with peptide fragments slightly inhibited both

• membrane potential, mitochondrial permeability transition and lipid peroxidation. Results and Discussion The starting N-substituted tetrahydro-γ-carbolines 3a–d containing a terminal alkyne group were prepared in good yields by heating compounds 1a–d [12][13] with propargyl acrylate (2) in the presence of

• described the conjugation of N-substituted tetrahydro-γ-carbolines containing a terminal alkyne group 3a–d with various azidopeptides 5 (prepared by Ugi multicomponent reaction) through the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition. The activity of the obtained compounds on rat liver mitochondria

Triphenylene discotic liquid crystal trimers synthesized by Co₂(CO)₈-catalyzed terminal alkyne [2 + 2 + 2] cycloaddition

• Bin Han,
• Ping Hu,
• Bi-Qin Wang,
• Carl Redshaw and
• Ke-Qing Zhao

Beilstein J. Org. Chem. 2013, 9, 2852–2861, doi:10.3762/bjoc.9.321

• trimers using Co2(CO)8-catalyzed terminal alkyne [2 + 2 + 2] cycloaddition reaction is reported. The trimers consist of three triphenylene discotic units linked to a central 1,2,4-trisubstituted benzene ring via flexible spacers. The trimers were synthesized in the yields up to 70% by mixing the monomers

• and stabilization of the discotic columnar mesophase. Conclusion The synthesis and mesomorphism of two new mono-functionalized triphenylene discotic monomers and four discotic trimers is reported. The trimers have been successfully synthesized for the first time by using a Co2(CO)8-catalyzed terminal

• alkyne [2 + 2 + 2] cycloaddition reaction in moderate yields. Three of the four 1,2,4-trisubstituted benzene-cored discotic trimers have shown stable Colho and Colro mesophases and wide mesophase ranges including room temperature. The connecting linker group to the triphenylene and the spacer length to

Total synthesis of the endogenous inflammation resolving lipid resolvin D2 using a common lynchpin

• John Li,
• May May Leong,
• Alastair Stewart and
• Mark A. Rizzacasa

Beilstein J. Org. Chem. 2013, 9, 2762–2766, doi:10.3762/bjoc.9.310

• stereoisomer analogues of RvD2 (1). Removal of the TIPS group with TBAF gave terminal alkyne 12. Alkyne 12 then underwent smooth hydrozirconation utilizing the procedure reported by Negishi [24] were ZrCp2HCl is generated in situ by reduction of ZrCp2Cl2 with DIBALH in THF. Iodinolysis of the zirconium species

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• Huisgen’s azide–alkyne cycloaddition (CuAAC reaction). In fact, the catalytic effect of copper ions had first been mentioned by L’Abbé in 1984 [7], but had henceforth been overlooked until Meldal presented a copper(I)-catalyzed solid-phase synthesis of 1,2,3-triazoles. In this procedure, the terminal alkyne

Ambient gold-catalyzed O-vinylation of cyclic 1,3-diketone: A vinyl ether synthesis

• Yumeng Xi,
• Boliang Dong and
• Xiaodong Shi

Beilstein J. Org. Chem. 2013, 9, 2537–2543, doi:10.3762/bjoc.9.288

• [22]. The internal alkyne (1-phenyl-1-propyne), which was usually much less reactive than the terminal alkyne, was also tested. As expected, no reaction occurred at room temperature under the optimal conditions. To our delight, the desired products 8 were obtained while refluxing at 60 °C for 48 h

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• a nucleophilic intramolecular attack of the carboxy moiety on the activated alkyne. 1,2-Migration of the ester affording a gold–carbene of type A is usually preferred when a terminal alkyne is used [38][39][40]. Based on this concept, several groups have shown that the resulting carbenoid

Gold(I)-catalyzed 6-endo hydroxycyclization of 7-substituted-1,6-enynes

• Ana M. Sanjuán,
• Alberto Martínez,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2013, 9, 2242–2249, doi:10.3762/bjoc.9.263

• and co-workers, as substrates in the identification of new reactivities catalyzed by gold and other transition metal complexes [5][6][7][8][9][10][11][12][13]. Cyclopropyl metal carbenes II are usually formed by exo-dig processes from enynes I bearing a terminal alkyne, which in the absence of

Gold-catalyzed glycosidation for the synthesis of trisaccharides by applying the armed–disarmed strategy

• Abhijeet K. Kayastha and
• Srinivas Hotha

Beilstein J. Org. Chem. 2013, 9, 2147–2155, doi:10.3762/bjoc.9.252

• glycosidation at ambient temperature. Accordingly, a panel of alkynylated glycosyl donors (15a–j) was synthesized and subjected to the glycosidation with three widely available gold salts, namely AuBr3, AuCl3 and HAuCl4, at 25 °C for 12 h in acetonitirile (Table 1). Substitutions at the terminal alkyne carbon

Post-Ugi gold-catalyzed diastereoselective domino cyclization for the synthesis of diversely substituted spiroindolines

• Amit Kumar,
• Dipak D. Vachhani,
• Sachin G. Modha,
• Sunil K. Sharma,
• Virinder S. Parmar and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2013, 9, 2097–2102, doi:10.3762/bjoc.9.246

• only the R-isomer of the Ugi-adduct 5a to simplify the discussion. The cationic gold coordinates with the terminal alkyne which becomes activated for a nucleophilic attack. This can occur from both sides of the indole core. When the attack occurs from the back side of the indole core, spiro

Gold-catalyzed reaction of oxabicyclic alkenes with electron-deficient terminal alkynes to produce acrylate derivatives

• Yin-wei Sun,
• Qin Xu and
• Min Shi

Beilstein J. Org. Chem. 2013, 9, 1969–1976, doi:10.3762/bjoc.9.233

• terminal alkyne 2a, we first used PPh3AuCl as a catalyst, AgSbF6 as an additive, and toluene as a solvent to examine the reaction outcome. Acrylate derivative 3a was formed with (Z)-configuration in 11% yield (Table 1, entry 1). In this reaction, naphthalen-1-ol was also obtained with 44% yield as the

• impaired the reaction outcome (Table 3, entries 1 and 7). Increasing the steric hindrance of the ester group improved the yields of 3 (Table 3, entries 4 and 5). The usage of but-3-yne-2-one (terminal alkyne ketone) 2i as a substrate gave the corresponding 3i with (E)-configuration in 48% yield (Scheme 2

• electron-deficient terminal alkynes. The reaction with terminal alkyne 2i as a substrate. The reaction with naphthalen-1-ol (5) as a substrate. The proposed mechanism for Au(I)-catalyzed reaction. Initial screening of the reaction conditions. Further screening of the reaction conditions. Substrate scope of

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

• rationalized in the next paragraph. In the case of pivalate 3c with a terminal alkyne (entry 2), the use of this bulky acyl group instead of acetyl is to curtail the hydrolytic formation of the corresponding α-ketoaldehyde. In many cases the ratios of 5-OAc and 5-H were high with IPrAuNTf2 as the catalyst; for

The application of a monolithic triphenylphosphine reagent for conducting Ramirez gem-dibromoolefination reactions in flow

• Kimberley A. Roper,
• Malcolm B. Berry and
• Steven V. Ley

Beilstein J. Org. Chem. 2013, 9, 1781–1790, doi:10.3762/bjoc.9.207

• -dibromovinyl)benzene (3) in 84% yield. Triphenylphosphine oxide (4) was also isolated from the reaction as a byproduct. These gem-dibromoolefin products are particularly important intermediates in the one carbon homologation of an aldehyde into the corresponding terminal alkyne, known as the Corey–Fuchs

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• ethylenediamine complex of lithium acetylide in a 1:1 THF/DMSO solvent mixture at 0 °C allowed the terminal alkyne to be accessed in 84% yield without rearrangement to the internal alkyne. Silyl protection afforded alkyne 50, which was prone to decomposition upon extended storage, even at −20 °C. Hydrozirconation

Preparation of optically active bicyclodihydrosiloles by a radical cascade reaction

• Koichiro Miyazaki,
• Yu Yamane,
• Ryuichiro Yo,
• Hidemitsu Uno and
• Akio Kamimura

Beilstein J. Org. Chem. 2013, 9, 1326–1332, doi:10.3762/bjoc.9.149

• -carbonyl radical that underwent radical cyclization to a terminal alkyne unit. The resulting vinyl radical attacked the silicon atom in an SHi manner to give dihydrosilole. The reaction preferentially formed trans isomers of bicyclosiloles with an approximately 7:3 to 9:1 selectivity. Keywords

Titanium-mediated reductive cross-coupling reactions of imines with terminal alkynes: An efficient route for the synthesis of stereodefined allylic amines

• Kebin Mao,
• Guoqin Fan,
• Yuanhong Liu,
• Shi Li,
• Xu You and
• Dan Liu

Beilstein J. Org. Chem. 2013, 9, 621–627, doi:10.3762/bjoc.9.69

• undergoes an unexpected 1,3-amino migration on silica gel during the column chromatography. Keywords: allylic amine; azatitanacyclopentene; reductive cross-coupling; regioselectivity; terminal alkyne; titanium-imine complex; Introduction Allylic amines are fundamental three-carbon building blocks in

• that, in turn, reacted with alkynes to give allylic amines after hydrolysis of the resulting azatitanacyclopentenes [35]. In this report, a terminal alkyne showed excellent regioselectivity and much better reactivity than internal alkynes. But only one successful example using a terminal alkyne

• imine with terminal alkyne. Synthesis of allylic amines 5q and 6q. Synthesis of allylic amine 9 by iodonolysis of azatitanacyclopentene 4g. Synthesis of various allylic amines by titanium-mediated coupling reactions of imine 2a with different terminal alkynes. Synthesis of various allylic amines by

End-labeled amino terminated monotelechelic glycopolymers generated by ROMP and Cu(I)-catalyzed azide–alkyne cycloaddition

• Ronald Okoth and
• Amit Basu

Beilstein J. Org. Chem. 2013, 9, 608–612, doi:10.3762/bjoc.9.66

• terminal alkyne [20][21]. For our purposes the later method was attractive as we could follow the reaction by monitoring the disappearance of the azide asymmetric stretch at 2100 cm−1 by IR spectroscopy. As shown in Scheme 1, reaction of the ROMP polymer 6 with excess amino–azide linker 8 [22] (2

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• and aryl(alkyl)acetylenes. Synthesis of estrogen receptor antagonist. Cobalt-catalyzed allylzincation of aryl-substituted alkynes. Silver-catalyzed alkylmagnesiation of terminal alkyne. Proposed mechanism of silver-catalyzed alkylmagnesiation. Zirconium-catalyzed ethylzincation of terminal alkenes

Radical zinc-atom-transfer-based carbozincation of haloalkynes with dialkylzincs

• Fabrice Chemla,
• Florian Dulong,
• Franck Ferreira and
• Alejandro Pérez-Luna

Beilstein J. Org. Chem. 2013, 9, 236–245, doi:10.3762/bjoc.9.28

• prepared by iodinating (AgNO3/NIS) the terminal alkyne of enoate 3c prepared from propargyl alcohol (1c) and acrylate 2. According to our previously optimized conditions for the 1,4-addition/carbozincation reaction of dialkylzincs with β-(propargyloxy)enoates [37][38], bromoalkyne 3a was treated with Et2Zn

Peptoids and polyamines going sweet: Modular synthesis of glycosylated peptoids and polyamines using click chemistry

• Daniel Fürniss,
• Timo Mack,
• Frank Hahn,
• Sidonie B. L. Vollrath,
• Katarzyna Koroniak,
• Ute Schepers and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 56–63, doi:10.3762/bjoc.9.7

• -alkylation with 5-chloropent-1-yne to insert the terminal alkyne moiety. To accomplish that, we used 10.0 equiv of alkyne and 15.0 equiv of K2CO3 in DMF; the reaction led to resin 9 with virtually quantitative yield, as shown in Scheme 1. For the CuAAC with the azides moieties 4, 6 and 7, respectively, we

On the proposed structures and stereocontrolled synthesis of the cephalosporolides

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2012, 8, 1287–1292, doi:10.3762/bjoc.8.146

• this spiroketal core. Our synthesis of the reported structure of cephalosporolide H (1) and its spiroketal isomer (1b) are outlined in Scheme 2. The synthesis starts from D-pantolactone (4), which was converted into terminal alkyne 5 [32]. Alkyne 5 was coupled with (R)-1,2-epoxynonane to obtain

• , and it is worth noting that NOE and NOESY experiments conducted on both isomers were inconclusive in attempts to differentiate them: similar NOESY cross-peaks were observed from both isomers. We prepared the two remaining core diastereomers by similar routes (Scheme 3), starting by coupling terminal

• alkyne 5 with (S)-1,2 epoxynonane. Gold-catalyzed cycloisomerization (with desilylation) provided spiroketal diols 10a and 10b in a 32:68 ratio and in 89% total yield. Major spiroketal 10b could be converted to 10a in 15:1 dr by zinc-catalyzed isomerization. Both isomers (10a and 10b) were independently

Parallel solid-phase synthesis of diaryltriazoles

• Matthias Wrobel,
• Jeffrey Aubé and
• Burkhard König

Beilstein J. Org. Chem. 2012, 8, 1027–1036, doi:10.3762/bjoc.8.115

• L-ascorbic acid (0.5 equiv) as reducing agent and copper(II) sulfate pentahydrate (10 mol %). After the terminal alkyne (4 equiv) was added, the reaction mixture was stirred for 22 h at room temperature. The resin was washed with dimethylformamide, methanol and dichloromethane (each solvent 2 mL/100

Parallel and four-step synthesis of natural-product-inspired scaffolds through modular assembly and divergent cyclization

• Hiroki Oguri,
• Haruki Mizoguchi,
• Hideaki Oikawa,
• Aki Ishiyama,
• Masato Iwatsuki,
• Kazuhiko Otoguro and
• Satoshi Ōmura

Beilstein J. Org. Chem. 2012, 8, 930–940, doi:10.3762/bjoc.8.105

• module 3, we then synthesized precursors 45 and 46 with a terminal alkyne and a furan ring, respectively, by using amine building blocks 43 and 44 according to the reported procedure [22]. The Rh(II)-catalyzed tandem reactions of 45 and 46 again proceeded at module 3 to produce cyclized products 47 and

An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• . The cycloaddition precursors were then subjected to the optimized microwave-promoted cycloadditions to give the final cycloadducts 14 (Scheme 6 and Table 4). Tertiary propargyl amides 13a, 13d, and 13e with terminal alkyne dienophiles all showed comparable reactivity (Table 4, entry 1, 4, and 5

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

• still-operative palladium complex. To do so, a terminal alkyne and caesium carbonate were added to the reaction mixture containing the newly formed 4-iodopyrrole, and the reaction temperature was increased to 70 °C (Scheme 17) [17]. Grigg and coworkers reported a three-component cascade process for the

• -step reaction with, first, a Sonogashira coupling of o-haloanilines with terminal alkynes, followed by a cyclization reaction of the resulting 2-alkynyaniline derivatives [26][27]. A strategy for the preparation of indoles through a three-component reaction consisted of generating the terminal alkyne