Regioselective palladium-catalyzed ring-opening reactions of C1-substituted oxabicyclo[2,2,1]hepta-2,5-diene-2,3-dicarboxylates

• Michael Edmunds,
• Mohammed Abdul Raheem,
• Rebecca Boutin,
• Katrina Tait and
• William Tam

Beilstein J. Org. Chem. 2016, 12, 239–244, doi:10.3762/bjoc.12.25

• the steric bulk on the bridgehead carbon decreased the yield. These reactions were found to be highly regioselective, giving only one of the two possible regioisomers in all cases. A diverse collection of novel, highly substituted biphenyl derivatives were obtained. Keywords: aryl iodides

• regioselectivity of the reaction. Two regioisomers are possible for this reaction based on whether the aryl group is added to carbon a or carbon b of 2 (Scheme 3). Our group recently investigated the effect of C1 substitution, with ethyl and methoxycarbonyl substituents, on the palladium-catalyzed ring-opening

• regioisomers, depending on whether the aryl group adds to Ca or Cb. In all cases, only one regioisomer was seen as a result of the addition of the aryl group to Ca. Cleavage of the β-oxygen gives the ring-opened intermediate 9. The palladium species is reduced, producing the final intermediate 10 and

Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen

• Hans Sterckx,
• Johan De Houwer,
• Carl Mensch,
• Wouter Herrebout,
• Kourosch Abbaspour Tehrani and
• Bert U. W. Maes

Beilstein J. Org. Chem. 2016, 12, 144–153, doi:10.3762/bjoc.12.16

• , entries 10 and 11). When investigating regioisomeric substrates featuring chloro substituents in all possible positions of the pyridine ring only the 4-Cl (pKa ≈ 3.8, Table 2, entries 15 and 16) substrate reaches full conversion under the standard conditions. The 3-Cl and 5-Cl regioisomers have a similar

Supramolecular structures based on regioisomers of cinnamyl-α-cyclodextrins – new media for capillary separation techniques

• Gabor Benkovics,
• Ondrej Hodek,
• Martina Havlikova,
• Zuzana Bosakova,
• Pavel Coufal,
• Milo Malanga,
• Eva Fenyvesi,
• Andras Darcsi,
• Szabolcs Beni and
• Jindrich Jindrich

Beilstein J. Org. Chem. 2016, 12, 97–109, doi:10.3762/bjoc.12.11

• This work focuses on the preparation and application of supramolecular structures based on mono-cinnamyl-α-cyclodextrins (Cin-α-CD). Pure regioisomers of Cin-α-CD having the cinnamyl moiety at the 2-O- or at the 3-O-position, respectively, were prepared, characterized and applied in capillary

• the regioisomers. The ability of the monomers to self-assemble was proved by various methods including NMR spectroscopy and dynamic light scattering (DLS). The light scattering experiments showed that the monomer units have distinguishable ability to form supramolecular structures in different

• solvents and the size distribution of the aggregates in water can be easily modulated using different external stimuli, such as temperature or competitive guest molecules. The obtained results indicated that the two regioisomers of Cin-α-CD formed different supramolecular assemblies highlighting the fact

Assembly of synthetic Aβ miniamyloids on polyol templates

• Sebastian Nils Fischer and
• Armin Geyer

Beilstein J. Org. Chem. 2015, 11, 2646–2653, doi:10.3762/bjoc.11.284

• correlation. Nuclear magnetic resonance spectroscopy is the analytical method of choice not only to characterize the conversion of template and peptide or to differentiate regioisomers, but also because it can detect noncovalent interactions between peptide strands by NOE contacts or other techniques. The

Synthesis of bi- and bis-1,2,3-triazoles by copper-catalyzed Huisgen cycloaddition: A family of valuable products by click chemistry

• Zhan-Jiang Zheng,
• Ding Wang,
• Zheng Xu and
• Li-Wen Xu

Beilstein J. Org. Chem. 2015, 11, 2557–2576, doi:10.3762/bjoc.11.276

• to biological activity [5][6][7][8]. Originally, this transformation was typically carried out at high temperature and resulted in a mixture of the 1,4 and 1,5 regioisomers (Scheme 1). Fortunately, representing a milestone in this field, the application of Cu(І) as the catalyst was reported by

Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

• David Porter,
• Belinda M.-L. Poon and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 2549–2556, doi:10.3762/bjoc.11.275

• regioisomers in the hetero-Diels–Alder reaction with nitroso compounds, yet Cenini et al. only detected one isomer. From this observation they concluded that their Ru-catalysed amination reaction and the Diels–Alder reactions were occurring ‘on metal’ without generation of a free nitroso species [57]. In

Synthesis of D-fructose-derived spirocyclic 2-substituted-2-oxazoline ribosides

• Madhuri Vangala and
• Ganesh P. Shinde

Beilstein J. Org. Chem. 2015, 11, 2289–2296, doi:10.3762/bjoc.11.249

• carbohydrate chemistry, they are versatile intermediates in the synthesis of N-linked glycoproteins [20][21][22]. In the context of carbohydrate chemistry, there are two possible regioisomers for glycooxazolines. Firstly, the C1 O-linked 1,2-glycooxazolines (Figure 1, 5) are formed by intramolecular

Efficient synthesis of π-conjugated molecules incorporating fluorinated phenylene units through palladium-catalyzed iterative C(sp²)–H bond arylations

• Fatiha Abdelmalek,
• Fazia Derridj,
• Safia Djebbar,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2015, 11, 2012–2020, doi:10.3762/bjoc.11.218

• example, using 4-bromobenzonitrile or ethyl 4-bromobenzoate, the coupling products 7 and 8 were isolated in 70% and 64% yields, respectively. However, other regioisomers were detected in the crude mixtures in trace amounts (e.g., 11–16%), which resulted from the activation of the furyl C–H bond. In

• contrast to these examples, when the reaction was performed with a heteroaryl bromide such as 3-bromopyridine, the two regioisomers 9a and 9b were obtained in 45:55 ratio. On the other hand, it is well known that the C–H bond at the C-3 position of the benzofuran is very reactive in palladium-catalyzed

• fluorine atom might be arylated under this reaction conditions. Using 4-bromobenzaldehyde as coupling partner, a mixture of two regioisomers in 82:18 ratio was obtained, and the C5 arylation product 25 (major regioisomer) was isolated after flash chromatography in 53% yield as pure product. It is important

Stereochemistry of ring-opening/cross metathesis reactions of exo- and endo-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitriles with allyl alcohol and allyl acetate

• Piotr Wałejko,
• Michał Dąbrowski,
• Lech Szczepaniak,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 1893–1901, doi:10.3762/bjoc.11.204

• total ratio of 1-2 vs 1-3 products in most experiments was the same (ca. 1:2), except entries 10, 11, 12, and 14, where the portion of the 1-3 regioisomers was higher (in entry 11 even 1:4). According to Arjona et al. [20] the observed regioselectivity comes from the steric hindrance of the –CN group

Qualitative evaluation of regioselectivity in the formation of di- and tri-6-O-tritylates of α-cyclodextrin

• Keisuke Yoshikiyo,
• Yoshihisa Matsui and
• Tatsuyuki Yamamoto

Beilstein J. Org. Chem. 2015, 11, 1530–1540, doi:10.3762/bjoc.11.168

• of α-CD involves three regioisomers, that are, 6A,6B-, 6A,6C-, and 6A,6D-di-O-tritylates (AB-, AC-, and AD-isomers, respectively), as shown in Scheme 1. These regioisomers were well separated and characterized [13]. The tri-6-O-tritylate of α-CD involves four regioisomers, that are 6A,6B,6C-, 6A,6B

• ,6D-, 6A,6B,6E-, and 6A,6C,6E-tri-O-tritylates (ABC-, ABD-, ABE-, and ACE-isomers, respectively, Scheme 1). Among them, only a symmetrical molecule of the ACE-isomer was separated and characterized [9]. The tetratritylate of α-CD involves three regioisomers, among which 6A,6B,6D,6E-tetra-O-tritylate

• direction of literature [9], and separated by means of reversed-phase column chromatography. Three regioisomers of di-6-O-trityl-α-CD obtained gave well-separated peaks in UFLC (ultra-fast liquid chromatography) experiment (Figure 1), details of which will be described in the Experimental part. Four

Intermolecular addition reactions of N-alkyl-N-chlorosulfonamides to unsaturated compounds

• Gerold Heuger and
• Richard Göttlich

Beilstein J. Org. Chem. 2015, 11, 1226–1234, doi:10.3762/bjoc.11.136

• HCl after the radical addition due to the high reaction temperature, the formation of regioisomers of 12 and especially the formation of 13 can be explained by a halonium-ion transfer to the alkene. This could produce an chloro-substituted alkene 14, which in a second step would undergo radical

New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes

• Rym Hassani,
• Mahjoub Jabli,
• Yakdhane Kacem,
• Jérôme Marrot,
• Damien Prim and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2015, 11, 1175–1186, doi:10.3762/bjoc.11.132

• to separate the later regioisomers by column chromatography or preparative TLC on silica gel were unsuccessful. According to the literature, the PPh3 adducts of cyclopalladated oxazolines have the trans (N,P) geometry [30][31]. In addition, the palladacycles with oxazoline ligands exists in endo and

• exo regioisomers. Results obtained in the present study show that naphthyl-oxazoline has a tendency to form exclusively endo-cyclic complexes with the C=N bond within a palladacycle. Furthermore, NMR data analyses demonstrate that the five-membered palladacycle 5a was preferentially formed upon the

Synthesis of novel N-cyclopentenyl-lactams using the Aubé reaction

• Madhuri V. Shinde,
• Rohini S. Ople,
• Ekta Sangtani,
• Rajesh Gonnade and
• D. Srinivasa Reddy

Beilstein J. Org. Chem. 2015, 11, 1060–1067, doi:10.3762/bjoc.11.119

• substituted cyclic ketones to give corresponding lactam products in only moderate yields. Unfortunately, in most cases, the desired lactams could not be isolated in pure form and were contaminated with cleaved secondary amides, diastereomers, regioisomers, etc. Finally, the reaction of the constrained

Synthesis of carbohydrate-scaffolded thymine glycoconjugates to organize multivalency

• Anna K. Ciuk and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2015, 11, 668–674, doi:10.3762/bjoc.11.75

• products (cf. Supporting Information File 1). Both regioisomers can consist of four different stereoisomers, two cis and two trans isomers according to the relative steric orientation of the thymine methyl groups. It can be assumed that the irradiation of 7 in diluted solution favors the syn

Metal-free one-pot synthesis of 2-substituted and 2,3-disubstituted morpholines from aziridines

• Hongnan Sun,
• Binbin Huang,
• Run Lin,
• Chao Yang and
• Wujiong Xia

Beilstein J. Org. Chem. 2015, 11, 524–529, doi:10.3762/bjoc.11.59

• -disubstituted aziridines (acyclic and/or cyclic ones), separable mixtures of regioisomers 3l,m and 4l,m were obtained arising from isomeric ring opening (Table 2, entries 12 and 13). We speculated that the observed regioselectivity might depend on the combined action of electronic effects and the position of

Eosin Y-catalyzed visible-light-mediated aerobic oxidative cyclization of N,N-dimethylanilines with maleimides

• Zhongwei Liang,
• Song Xu,
• Wenyan Tian and
• Ronghua Zhang

Beilstein J. Org. Chem. 2015, 11, 425–430, doi:10.3762/bjoc.11.48

• formation of a mixture of regioisomers 3q1 and 3q2 with 81% combined yield. The major product was the sterically more hindered 3q1 [43][44][45]. On the basis of our observations and literature reported [19][36][38][43][44], a proposed mechanism for the formation of the corresponding tetrahydroquinolines 3

C-5’-Triazolyl-2’-oxa-3’-aza-4’a-carbanucleosides: Synthesis and biological evaluation

• Roberto Romeo,
• Caterina Carnovale,
• Salvatore V. Giofrè,
• Maria A. Chiacchio,
• Adriana Garozzo,
• Emanuele Amata,
• Giovanni Romeo and
• Ugo Chiacchio

Beilstein J. Org. Chem. 2015, 11, 328–334, doi:10.3762/bjoc.11.38

• –alkyne cycloadditions, no traces of 1,5-regioisomers were observed [47][48]. The structure of the obtained compounds was assessed according to 1H NMR, 13C NMR and MS data. In particular, the 1H NMR spectra of 5-methyl-1-[(3RS,5SR)-2-methyl-3-(1H-1,2,3-triazol-1-ylmethyl)isoxazolidin-5-yl]pyrimidine-2,4

Switching the reaction pathways of electrochemically generated β-haloalkoxysulfonium ions – synthesis of halohydrins and epoxides

• Akihiro Shimizu,
• Ryutaro Hayashi,
• Yosuke Ashikari,
• Toshiki Nokami and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2015, 11, 242–248, doi:10.3762/bjoc.11.27

• + or I+ and DMSO to unsymmetrically substituted olefins 2c and 2d regioselectively gave bromohydrins as single regioisomers (Table 2, entries 5–10). The regioselectivity of the products can be explained by the stability of carbocations (benzyl > secondary > primary). In the case of terminal alkene 2c

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

•  24 [72]. In this example, 1,2-benzoquinone derivatives are generated in the presence of ketene N,O-acetals 70. Out of four possible regioisomers, 71a and 71b are exclusively formed (in ratios 71a/71b between 1:1 and 1:2). In a follow-up study, unreacted α-arylated ketene N,O-acetal intermediates (63

Regio- and stereoselective synthesis of new diaminocyclopentanols

• Evgeni A. Larin,
• Valeri S. Kochubei and
• Yuri M. Atroshchenko

Beilstein J. Org. Chem. 2014, 10, 2513–2520, doi:10.3762/bjoc.10.262

• aminocyclopentanols 8c and 8d (Supporting Information File 1). In every experiment, 1,2-trans-2,3-cis-aminocyclopentanols, arising from opening of epoxide 3a at C1, were the only regioisomers isolated. The stereo- and regiochemistry of 8a and 8d were assigned by 2D NMR (HSQC-DEPT, 1H,1H COSY and NOESY experiments

• displayed poor regioselectivity. In fact, a mixture of the separable regioisomers 9a–d and 10a–d were obtained, where the major products 9a–d were formed due to the attack of the nucleophile at the C1-oxirane carbon atom. In case of aliphatic cyclic amines (morpholine (7a) and N-acetylpiperazine (7c)), the

• nucleophilicity. Moreover, there was not much effect on the outcome of the reactions conducted either under solvent-free conditions or using DMSO as a solvent. The regioisomers 9a–d and 10a–d were isolated through column chromatographic separation and fully characterized in order to avoid ambiguity. The

Facile synthesis of 1H-imidazo[1,2-b]pyrazoles via a sequential one-pot synthetic approach

• András Demjén,
• Márió Gyuris,
• János Wölfling,
• László G. Puskás and
• Iván Kanizsai

Beilstein J. Org. Chem. 2014, 10, 2338–2344, doi:10.3762/bjoc.10.243

• have predominantly been described as 5H-imidazo[1,2-b]pyrazoles with an endo double bond (and not as 1H-imidazo[1,2-b]pyrazoles), but without 2D NMR-based support. However, the GBB-3CR of functionalized pyrazoles might lead to the formation of two regioisomers [24] and four different tautomeric forms

End group functionalization of poly(ethylene glycol) with phenolphthalein: towards star-shaped polymers based on supramolecular interactions

• Carolin Fleischmann,
• Hendrik Wöhlk and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 2263–2269, doi:10.3762/bjoc.10.235

• ) was then reacted with PP-N3 in a 1,3-diploar cycloaddition, which gave the desired phenolphthalein-functionalized mPEG-PP (see Scheme 2). Since the reaction was carried out in absence of copper(I) salts, a mixture of the 1,4- and 1,5-substituted triazole regioisomers was obtained. The host component

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• cyclopentenes as single regioisomers with high enantioselectivities. Interestingly, single amino acid-based phosphines were better than di-, tri-, and tetrapeptide-based catalysts. Of particular note, when they treated γ-substituted racemic allenoates with acyclic enones, unique dynamic kinetic asymmetric

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• secondary amines. In some cases, protection of the hydroxy groups in 94a was also necessary. The reactions between 3',5'-di-O-acetyl-5-iodo-2'-deoxyuridine (94b), long-chain 1,ω-dienes (e.g., deca-1,9-diene or tetradeca-1,13-diene) and morpholine afforded products as mixtures of regioisomers resulting from

Synthesis, characterization and DNA interaction studies of new triptycene derivatives

• Sourav Chakraborty,
• Snehasish Mondal,
• Rina Kumari,
• Sourav Bhowmick,
• Prolay Das and
• Neeladri Das

Beilstein J. Org. Chem. 2014, 10, 1290–1298, doi:10.3762/bjoc.10.130

• . Subsequently, derivatization of ethynyl-substituted triptycenes was studied to yield the respective propiolic acid and ethynylphosphine derivatives. Characterization of the newly functionalized triptycene derivatives and their regioisomers were carried out using FTIR and multinuclear NMR spectroscopy, mass

• interactions depends on the functionality of the substituents. However, there is no marked difference in the extent of interaction with DNA between a given pair of regioisomers. Results and Discussion Synthesis and characterization of ethynyl- and azide-substituted triptycenes. Using appropriate