Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• in the formation of a bridged tetracycle after initial Heck coupling followed by carbo-palladation and subsequent β-hydride elimination [69][70][71]. Double bond regioisomers (between C7 & C8 or C13 & C14) were obtained. Oxidation with DDQ yielded the 1,6-unsaturated ketone 72. Selective epoxidation

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

• for proline as a substrate (Table 1, entries 1 and 3). The 1,3-dipolar cycloaddition of unsymmetrical dipolarophiles such as acrylamides can occur via the two pathways A and B leading to the formation of the regioisomers 4 and 4’. In our case, spirooxindol 4 is exclusively formed. All new cycloadducts

• dipolarophiles 5 with non-stabilized azomethine ylides generated from isatins 1 and sarcosine/proline has led to spiropyrrolidines 6a,6b and spiropyrrolizidines 6c–6h in moderate to good yields. In this reaction also two regioisomers can be expected, but in all experiments solely the regioisomer 6 is isolated

Continuous-flow Heck synthesis of 4-methoxybiphenyl and methyl 4-methoxycinnamate in supercritical carbon dioxide expanded solvent solutions

• Phei Li Lau,
• Ray W. K. Allen and
• Peter Styring

Beilstein J. Org. Chem. 2013, 9, 2886–2897, doi:10.3762/bjoc.9.325

• used was either styrene to yield the stilbenes 1 or methyl acrylate to yield the cinnamate ester 2. For each reaction there are three possible regioisomers. The thermodynamically favoured trans- (t) isomer is most common in standard organic solvents although under certain conditions the cis- (c) isomer

Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate

• James A. B. Laurenson,
• John A. Parkinson,
• Jonathan M. Percy,
• Giuseppe Rinaudo and
• Ricard Roig

Beilstein J. Org. Chem. 2013, 9, 2660–2668, doi:10.3762/bjoc.9.301

• overlaps with the published syntheses of 6-deoxy-6-fluorohexoses from methyl sorbate [13]. The main benefits of the crotonic acid route are the absence of regioisomers as the double bond is installed after the asymmetric oxidation and the potential to deliver all of the 6-deoxy-6-fluorohexose isomers, as

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

• , though in low yield. Two regioisomers were isolated, which were assigned as 8a and 8b (Scheme 3A). Diphenylacetylene gave trace amounts of the desired product under the identical conditions. Several diketones were tested to explore the scope of nucleophiles. The 1,3-cyclohexanedione derivative worked

Flexible synthesis of anthracycline aglycone mimics via domino carbopalladation reactions

• Markus Leibeling and
• Daniel B. Werz

Beilstein J. Org. Chem. 2013, 9, 2194–2201, doi:10.3762/bjoc.9.258

• for the aspired synthesis [10][11][12][13]. A classical synthesis was published in 1988 by Hansen where a silyl-substituted diene 3 was used for the [4 + 2]-cycloaddition (Scheme 1) [14]. Starting from bisquinone 4 the annulated ring system 5 is obtained in a 1:1 mixture of cis-endo regioisomers

• . Subsequent aromatization of the C-ring and several additional steps generated the daunomycin aglycon 6 and the corresponding isodaunomycin aglycone (dependent on the regioisomers) in a total of 16 steps. In 2003, Saá published a concise route to anthraquinone derivatives by using an intramolecular dehydro

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

• of regioisomers (C2/C3 1.1:1) [22]. We disclose herein the regioselective 1,4-addition of the CF3 group into simple conjugated acyclic enones including chalcones using S-(trifluoromethyl)diphenylsulfonium salt 3 and a copper system in 11–37% yields (12 examples). Results and Discussion We initiated

• regioisomers and/or byproducts was detected in a crude mixture analyzed by 19F NMR. Under the best conditions shown in entry 10, we re-examined the reaction, but in the presence of TEMPO. The product formation was inhibited by TEMPO and O-trifluoromethylated TEMPO was detected in 2% by 19F NMR analysis (Table

• of CuCF3 species to provide the 1,4-adduct 2 in low to moderate yield. Although the true reactive species including CF3 radical and/or CuCF3 are not clear, the naked CF3 radical should be ruled out since high regioselectivity was observed, otherwise, a 1:1 mixture of regioisomers (C2/C3) should be

Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene

• Peter A. Wade,
• Alma Pipic,
• Matthias Zeller and
• Panagiota Tsetsakos

Beilstein J. Org. Chem. 2013, 9, 2137–2146, doi:10.3762/bjoc.9.251

• substitution patterns. We were also interested in determining the double bond specificity of the Denmark Diels–Alder reaction for unsymmetrical dienes. Previous work on cyclopentadiene and cyclohexadiene has shown that the reaction can be quite specific to give one of two possible regioisomers [11][12]. In the

• case of 1-(2-propenyl)cyclohexene only one of four possible regioisomers was observed [1]. However, it was not clear what the outcome would be for a simple open-chain conjugated diene. Consequently, cycloaddition reactions of 3-methyl-1,3-pentadiene were examined. This diene has both trisubstituted and

• monosubstituted double bonds allowing for cycloaddition to give up to four regioisomers. It is commercially available both as an E,Z-mixture and as the pure E-isomer. The Z-isomer can be obtained from the E,Z-mixture by selective removal of the E-isomer via cycloaddition with maleic anhydride [13]. Results and

Gold(I)-catalyzed hydroarylation reaction of aryl (3-iodoprop-2-yn-1-yl) ethers: synthesis of 3-iodo-2H-chromene derivatives

• Pablo Morán-Poladura,
• Eduardo Rubio and
• José M. González

Beilstein J. Org. Chem. 2013, 9, 2120–2128, doi:10.3762/bjoc.9.249

• arising from the migratory cyclization against that deriving from a straight iodoalkyne arylation reaction. As for the substituents on the amine ring, more electron-donating ones gave rise to the formation of the heterocycle featuring a distribution of regioisomers that indicates less iodine shift. In

Acid, silver, and solvent-free gold-catalyzed hydrophenoxylation of internal alkynes

• Marcia E. Richard,
• Daniel V. Fraccica,
• Kevin J. Garcia,
• Erica J. Miller,
• Rosa M. Ciccarelli,
• Erin C. Holahan,
• Victoria L. Resh,
• Aakash Shah,
• Peter M. Findeis and
• Robert A. Stockland Jr.

Beilstein J. Org. Chem. 2013, 9, 2002–2008, doi:10.3762/bjoc.9.235

• solvent. Microwave heating with 1 or 7 as the catalyst (14.0 μmol, 5%). The yield of the addition product and ratio of regioisomers was determined by 1H NMR spectroscopy using anisole as an internal standard. Hydrophenoxylation of unactivated internal alkynes.a Supporting Information Supporting

Continuous flow photocyclization of stilbenes – scalable synthesis of functionalized phenanthrenes and helicenes

• Quentin Lefebvre,
• Marc Jentsch and
• Magnus Rueping

Beilstein J. Org. Chem. 2013, 9, 1883–1890, doi:10.3762/bjoc.9.221

• also tolerated, but nitro- and amino groups containing stilbenes showed low conversion or decomposition. Meta-substituted substrates gave inseparable regioisomers, and ortho-substitution led to low conversion. In the case of substrate 1e, a separable 1:1 mixture of regioisomers 2e and 2e’ was obtained

• , entry 3), whereas the reaction in acetonitrile resulted in a separable 1:1 mixture of regioisomers 2k and 2k’ (Table 4, entry 4). Finally, we decided to apply our photo-flow methodology in the synthesis of functionalised [5]helicenes and [6]helicenes. We identified 3-acetyl-9,10-dimethoxyphenanthrene

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization

• Guillaume Moreira,
• Laurence Charles,
• Mohamed Major,
• Florence Vacandio,
• Yohann Guillaneuf,
• Catherine Lefay and
• Didier Gigmes

Beilstein J. Org. Chem. 2013, 9, 1589–1600, doi:10.3762/bjoc.9.181

• presence of a mixture of cellobiose mono, di- and tri-acroylated, acrylic acid (resulting from the hydrolysis of acryloyl chloride), and free cellobiose. It is noteworthy that this reaction is not regioselective, so that several regioisomers are formed, which are very difficult to separate and quantify. BB

• reactive, but all regioisomers are possible. (Reversible) redox system of nitroxide. Hydrolysis of DMA in the presence of LiCl. Disproportionation of nitroxide 1 by acid treatment. Experimental redox potential of the oxidation (Eox) and of the reduction (Ered) in DMF and MeOH.a Acknowledgements The

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

• preserved in the transformation. Aliphatic epoxides are opened selectively (>95:5) at the terminal position. Although very high regioselectivity with respect to the alkyne is observed when R1 = Ph and R2 = Me, attempts to differentiate between aliphatic alkyne substituents lead to mixture of regioisomers

Coupling of C-nitro-NH-azoles with arylboronic acids. A route to N-aryl-C-nitroazoles

• Marta K. Kurpet,
• Aleksandra Dąbrowska,
• Małgorzata M. Jarosz,
• Katarzyna Kajewska-Kania,
• Nikodem Kuźnik and
• Jerzy W. Suwiński

Beilstein J. Org. Chem. 2013, 9, 1517–1525, doi:10.3762/bjoc.9.173

• consistent with the analysis of regioisomers of 1-substituted-C-nitropyrazoles presented by Larina and Lopyrev in their review on nitroazoles [35]. Table 1 contains exemplified structures of 3-nitro-, 4-nitro- and 5-nitropyrazole derivatives and shows the differences in chemical shifts of carbon atoms in

Efficient continuous-flow synthesis of novel 1,2,3-triazole-substituted β-aminocyclohexanecarboxylic acid derivatives with gram-scale production

• Sándor B. Ötvös,
• Ádám Georgiádes,
• István M. Mándity,
• Lóránd Kiss and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2013, 9, 1508–1516, doi:10.3762/bjoc.9.172

• of only 75%, whereas the use of additives at rt (conditions B) proved more efficient, with a yield of 97% (Table 1, entry 12). Triazoles 23–26 were obtained selectively as 1,4-disubstituted regioisomers. To understand the differences between the results obtained with the three different

Thiourea-catalyzed Diels–Alder reaction of a naphthoquinone monoketal dienophile

• Carsten S. Kramer and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 1414–1418, doi:10.3762/bjoc.9.158

• ]. Thereby, a mixture of regioisomers was always isolated. Regioisomer 5 was obtained diastereoselectively pure, the other isomer was received in a 3:1 (Table 1, entry 1) or 4:1 (Table 1, entry 2) mixture of 2a and 2b. The rather harsh conditions and the lack of selectivity in the cycloaddition of dienophile

Palladium-catalyzed synthesis of N-arylated carbazoles using anilines and cyclic diaryliodonium salts

• Stefan Riedmüller and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2013, 9, 1202–1209, doi:10.3762/bjoc.9.136

• byproducts from the crude reaction mixture. After a systematic structure determination by one- and two-dimensional NMR techniques as well as mass spectrometry, we elucidated the two byproducts as the two regioisomers 2'-bromo-N-(4-fluorophenyl)biphenyl-2-amine (7a, 12%) and 2'-bromo-N-(4-fluorophenyl

Intramolecular carbonickelation of alkenes

• Rudy Lhermet,
• Muriel Durandetti and
• Jacques Maddaluno

Beilstein J. Org. Chem. 2013, 9, 710–716, doi:10.3762/bjoc.9.81

• mixture of the three regioisomers 14–16 was recovered (Scheme 6). By contrast, under Larock’s conditions [33] [Pd(OAc)2 (5 mol %), Na2CO3, DMF, 80 °C], an even higher yield (90% after 2 days) was returned but consisted of a 1:1:1 mixture of the same three products 14–16. Replacing sodium carbonate by

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

• alkynes produced an inseparable mixture of two regioisomers in some cases [33] or could not give the desired products [34]. Sato et al. reported that a divalent titanium reagent generated by the Ti(OiPr)4/2 iPrMgX system reacted with arylaldimines to provide the corresponding (η2-imine)Ti(OiPr)2 complex

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

• carbamate moiety. Molecular structure of 9f (hydrogen atoms except of H9 and H10 are omitted for clarity). Possible regioisomers obtained in the carbocupration reaction of α-heterosubstituted acetylenes 1. Regioselective carbometallation of N-alkynylsulfonamide 2. Regioselective carbometallation of ynamide

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

• afford 2B or 2C (Scheme 8). Further transmetalation of vinyliron intermediate 2B or 2C with R′MgBr yielded the corresponding vinylmagnesium intermediate 2D. Therefore, selective synthesis of both regioisomers of allylic alcohols can be accomplished by simply choosing transition-metal catalysts (Cu or Fe

Polar reactions of acyclic conjugated bisallenes

• Reiner Stamm and
• Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 36–48, doi:10.3762/bjoc.9.5

• . We therefore took bisallene 5 and subjected it to MMPP treatment (fivefold excess). The reaction took place in acceptable yield (65%) and provided a mixture of two bis oxidation products, 40 and 41, in 5:1 ratio. Although the two regioisomers were separated on the analytical GC, the attempted

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

• of regioisomers in reaction 3. Instead of the 1,4-disubstituted triazoles obtained from copper(I) catalysis, the complex pentamethylcyclopentadienylbis(triphenylphosphine)ruthenium(II) chloride leads to 1,5-disubstituted triazole compounds [19]. 4-(Azidomethyl)benzoic acid functionalized Wang resin 7

Multistep organic synthesis of modular photosystems

• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2012, 8, 897–904, doi:10.3762/bjoc.8.102

• crude dibromo cNDA 32. Microwave-assisted reaction [15] with amines 14 and 15 gave the mixed cNDI 44 together with the symmetric side products. The obtained mixture of 2,6- and 3,7-regioisomers was not separated throughout the entire synthesis of photosystem 1. Nucleophilic aromatic substitution with

• (color coded) are indicated in eV against vacuum (−5.1 eV for Fc/Fc+), including triethanolamine (TEOA), used as mobile hole transporter. Synthesis of initiator 2. Synthesis of propagators 3 and 4. Synthesis of stack exchangers 5 and 6. Compounds 5, 6, 45 and 47 are mixtures of 2,6- and 3,7-regioisomers

• consistent with the experimental results. They will naturally contain defects. Synthesis of photosystem 1, stack exchange. R1 = SH or oxidized derivative, R1 = CH2CHCH2. 5 and 6 are mixtures of 2,6- and 3,7-regioisomers. Schematic overview over SOSIP and stack exchange. Acknowledgements We thank the

Facile isomerization of silyl enol ethers catalyzed by triflic imide and its application to one-pot isomerization–(2 + 2) cycloaddition

• Kazato Inanaga,
• Yu Ogawa,
• Yuuki Nagamoto,
• Akihiro Daigaku,
• Hidetoshi Tokuyama,
• Yoshiji Takemoto and
• Kiyosei Takasu

Beilstein J. Org. Chem. 2012, 8, 658–661, doi:10.3762/bjoc.8.73

• conditions (−10 °C), followed by the addition of methyl acrylate (5) at −78 °C, 6-methylbicyclo[4.2.0]octane 6 and its diastereomer were obtained in 86% and 6%, respectively (Scheme 2a). No formation of their regioisomers was observed. The obtained compound 6 is identical to the product in the reaction of 2a