Two-directional synthesis as a tool for diversity-oriented synthesis: Synthesis of alkaloid scaffolds

• Kieron M. G. O’Connell,
• Monica Díaz-Gavilán,
• Warren R. J. D. Galloway and
• David R. Spring

Beilstein J. Org. Chem. 2012, 8, 850–860, doi:10.3762/bjoc.8.95

• refer to the isolated yields of single compounds. (a) AlCl3 catalysed formation of tricyclic alkaloid 10 along with an X-ray crystal structure of 10; (b) base-mediated Dieckmann cyclisation of trans-8 employed by Stockman and co-workers in the synthesis of hippodamine [25]. (a) Optimal conditions to

Synthetic glycopeptides and glycoproteins with applications in biological research

• Ulrika Westerlind

Beilstein J. Org. Chem. 2012, 8, 804–818, doi:10.3762/bjoc.8.90

• monovalent derivative with the multivalent inhibitor [121]. The X-ray crystal structure of the cholera-toxin–GM1-ganglioside complex has shown that most of the protein contacts are given to the terminal galactose unit [122]. With this knowledge in hand, dendrimers based on readily available galactose

Stereoselective, nitro-Mannich/lactamisation cascades for the direct synthesis of heavily decorated 5-nitropiperidin-2-ones and related heterocycles

• Pavol Jakubec,
• Dane M. Cockfield,
• Madeleine Helliwell,
• James Raftery and
• Darren J. Dixon

Beilstein J. Org. Chem. 2012, 8, 567–578, doi:10.3762/bjoc.8.64

• ). Supporting Information File 153: X-ray crystal structure of compound 2m’. Supporting Information File 154: X-ray crystal structures of compounds 1g, 2, 2a’’, 6e and 11c. Acknowledgements We gratefully acknowledge Merck, Sharp and Dohme (Hoddesdon, U.K.) for a studentship (to D.M.C.); the EPSRC for a

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

• X-ray crystal structure of 4b, 6d,f and 7a (Figure 1) [18]. Compounds 6 and 7 are similar to the recently reported dihydropyridine dicarboxylate derivatives and are expected to act as photoinduced intramolecular electron-transfer systems [7][8]. Table 2 shows the UV–vis absorption–emission maxima of

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• by NMR comparison with the corresponding alanine-derived ring system, for which a structural proof was furnished by X-ray crystal-structure determination [18]. Due to the symmetry of the dimers, the NMR spectra display signals for only half of the total number of carbon and hydrogen nuclei

Synthesis of mesomeric betaine compounds with imidazolium-enolate structure

• Nina Gonsior,
• Fabian Mohr and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 390–397, doi:10.3762/bjoc.8.42

• C13H12Br2N2O3: C, 38.64; H, 2.99; N, 6.93; found: C, 38.65; H, 2.86; N, 6.59. X-ray crystal-structure analysis of 3 Single crystals of 3 were obtained by very slow evaporation of methylene chloride. They were mounted in inert oil and transferred to the cold gas stream of the diffractometer. Diffraction data

Aldol elaboration of 4,5,6,7-tetrahydroisoxazolo[4,3-c]pyridin-4-ones, masked precursors to acylpyridones

• Raymond C. F. Jones,
• Abdul K. Choudhury,
• James N. Iley,
• Mark E. Light,
• Georgia Loizou and
• Terence A. Pillainayagam

Beilstein J. Org. Chem. 2012, 8, 308–312, doi:10.3762/bjoc.8.33

• methods to reveal the cyclic tricarbonyl moiety in such compounds have been reported by us previously [9][10][11][12][13][14][15][16]. The 3-acyl-4-hydroxypyridin-2-one motif, example natural products and the isoxazolopyridone scaffolds. X-ray crystal structure of 3-(2-phenylethenyl)-4,5,6,7

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• ), illustrated in Figure 3, along with 3a [16]. To finally prove that the main product from thermal dehydration was indeed a trimer, Vicens reported the X-ray crystal structure of 3a in 1992 (Figure 4) demonstrating it to be exclusively in the bowl-shaped cone conformation [17]. In 1994, Hampton et al. used an

• when K2CO3 was used, the authors suggested that Na+ may play a templating role in addition to that of a deprotonating agent. The X-ray crystal structure of the product (Figure 9) shows that the carbonyl oxygen atoms point away from the cavity to create a large hydrophobic cavity. Extraction studies

• been ongoing since 1999 when Thuéry reported a complex of uranyl (UO22+) and 3a [62]. The X-ray crystal structure showed that the cation was threaded through a single macrocycle in what was, at the time, an unprecedented pseudotrigonal geometry, which included a weak interaction between the nitrogen of

Regioselectivity in the multicomponent reaction of 5-aminopyrazoles, cyclic 1,3-diketones and dimethylformamide dimethylacetal under controlled microwave heating

• Kamal Usef Sadek,
• Ramadan Ahmed Mekheimer,
• Tahany Mahmoud Mohamed,
• Moustafa Sherief Moustafa and
• Mohamed Hilmy Elnagdi

Beilstein J. Org. Chem. 2012, 8, 18–24, doi:10.3762/bjoc.8.3

• subsequently reacted with 5-aminopyrazole 1 at the exocyclic amino function, followed by cyclization through water loss to give 6 (route A). Formation of isomeric product 4, which would be formed by route B, was ruled out based on spectral and X-ray diffraction data. From the data of the X-ray crystal

• structure it can be concluded that the bridged head nitrogen has bond angles closer to those of sp3 nitrogen. One may thus conclude that the lone pair on this nitrogen atom does not contribute much to the actual state of the molecule and that charge-separated ions also do not contribute significantly

Structural conditions required for the bridge lithiation and substitution of a basic calix[4]arene

• Conrad Fischer,
• Wilhelm Seichter and
• Edwin Weber

Beilstein J. Org. Chem. 2011, 7, 1602–1608, doi:10.3762/bjoc.7.188

• new monobridge-substituted calix[4]arenes were characterized with respect to their conformational behaviour in solution and the X-ray crystal structure of one key intermediate is taken into consideration. Keywords: calixarene; lithiation; methylene bridge; supramolecular chemistry; X-ray structure

Asymmetric synthesis of quaternary aryl amino acid derivatives via a three-component aryne coupling reaction

• Elizabeth P. Jones,
• Peter Jones,
• Andrew J. P. White and
• Anthony G. M. Barrett

Beilstein J. Org. Chem. 2011, 7, 1570–1576, doi:10.3762/bjoc.7.185

• underwent hydrolysis to the corresponding valine dipeptides. NOESY correlation observed for 6a. X-ray crystal structure of 6b. Transition state analysis to explain the lack of diastereoselectivity at C-2. 3-Component coupling reactions of arynes. E+ = electrophile. Aryne mediated α-arylation of amino acids

Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

• Lukas Hintermann,
• Mauro Perseghini and
• Antonio Togni

Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166

• by external F–TEDA reagent at the central carbon of the enolate, diastereoselectively, from the face opposite to a shielding TADDOLate aryl group (Scheme 7, B→C). In order to arrive at a simple structural model of B, we used the coordinates from the X-ray crystal structure of the 1-naphthyl-TADDOL

Directed ortho,ortho'-dimetalation of hydrobenzoin: Rapid access to hydrobenzoin derivatives useful for asymmetric synthesis

• Inhee Cho,
• Labros Meimetis,
• Lee Belding,
• Michael J. Katz,
• Travis Dudding and
• Robert Britton

Beilstein J. Org. Chem. 2011, 7, 1315–1322, doi:10.3762/bjoc.7.154

• 1H NMR spectroscopy. The remainder of the material is recovered (R,R)-hydrobenzoin (3). Directed ortho,ortho'-dimetalation of (R,R)-hydrobenzoin (3). Formation of the tetralithio intermediate 8 and the X-ray crystal structure of the bis(siloxane) 19. Reaction of the tetralithio intermediate 8 with

• various electrophiles. Reactions of the diiodohydrobenzoin 12 and X-ray crystal structure of the dihydrosilepin 31. Cross coupling reactions of the bis(benzoxaborol) 20 and a short formal synthesis of (R,R)-Vivol (4). Optimization of the synthesis of the diiodohydrobenzoin 12. Supporting Information

Lithium phosphonate umpolung catalysts: Do fluoro substituents increase the catalytic activity?

• Anca Gliga,
• Bernd Goldfuss and
• Jörg M. Neudörfl

Beilstein J. Org. Chem. 2011, 7, 1189–1197, doi:10.3762/bjoc.7.138

• -ray crystal structure of 6. (M)-(S,S) and (P)-(R,R) pair of enantiomers; intermolecular O1–O2 distance 2.81 Å; intramolecular O1–O2 distance 2.83 Å. Ellipsoids correspond to 50% probability levels. Hydrogen atoms are omitted for clarity. X-ray crystal structure of 7. (M)-(S,S) and (P)-(R,R) pair of

• enantiomers; intermolecular O1–O2 distance 2.80 Å; intramolecular O1–O2 distance 2.81 Å. Ellipsoids correspond to 50% probability levels. Hydrogen atoms are omitted for clarity. 31P NMR of phosphonate 14 (a) and 15 (b). X-ray crystal structure of 15. (M)-(R,S) diastereomer; ellipsoids correspond to 50

• phosphonates. This can be explained by a weaker nucleophilic character of the phosphorus nucleophile, as a consequence of the increased s-character. Comparisons of phosphonates with different ring sizes show that the nine ring phosphonates result in higher yields than do the six and seven ring phosphonates. X

Scalable synthesis of (1-cyclopropyl)cyclopropylamine hydrochloride

• Sergei I. Kozhushkov,
• Alexander F. Khlebnikov,
• Rafael R. Kostikov,
• Dmitrii S. Yufit and
• Armin de Meijere

Beilstein J. Org. Chem. 2011, 7, 1003–1006, doi:10.3762/bjoc.7.113

• , otherwise the yield of 3 dropped dramatically, and the desired product was accompanied by 1,3-di(bicyclopropyl)urea (5) in up to 50% yield (Scheme 1). The structure of the latter was confirmed by an X-ray crystal structure analysis (Figure 1) [26]. The carbamate 3 was deprotected by treatment with hydrogen

• recrystallization of the residue from hexane/CHCl3; mp 159–161 °C. The structure of 5 was confirmed by X-ray crystal structure analysis [26]. 5: 1H NMR (300 MHz, CDCl3) δ 5.21 (br s, 2H, NH), 1.28–1.16 (m, 2H, 2 CH cPr-H), 0.73–0.61 (m AA'BB', 8H, 4 CH2, cPr-H), 0.44–0.41 and 0.17–0.13 (m AA'BB', 8H, 4 CH2, cPr-H

Gold-catalyzed propargylic substitutions: Scope and synthetic developments

• Olivier Debleds,
• Eric Gayon,
• Emmanuel Vrancken and
• Jean-Marc Campagne

Beilstein J. Org. Chem. 2011, 7, 866–877, doi:10.3762/bjoc.7.99

• equivalent of hydroxylamine was obtained. By using 2.1 equivalents of the Cbz- or PhSO2-protected hydroxylamines, compounds 24a–c were isolated in 67–79% yields as single diastereomers. Determination of the structures of 24 was a challenging task and could only be determined by an X-ray crystal structure

High chemoselectivity in the phenol synthesis

• Matthias Rudolph,
• Melissa Q. McCreery,
• Wolfgang Frey and
• A. Stephen K. Hashmi

Beilstein J. Org. Chem. 2011, 7, 794–801, doi:10.3762/bjoc.7.90

• phenol 10 was formed exclusively (Scheme 6). The structure was unambiguously confirmed by X-ray crystal structure analysis (Figure 1). It shows an interesting hydrogen bond-like interaction of the phenolic hydroxy group and the alkene unit. After changing the solvent from acetonitrile to CDCl3, and the

• diastereoisomers of 28 was identified as the anti-product 28a by an X-ray crystal structure analysis (Figure 2). The conversion of 16 with 5 mol % AuCl3 proceeded fast and gave exclusively phenol 18. No other products could be detected (Scheme 9). The two gold(III) complexes 34 [43] and 35 [37] as well as the

Stereogenic boron in 2-amino-1,1-diphenylethanol-based boronate–imine and amine complexes

• Sebastian Schlecht,
• Walter Frank and
• Manfred Braun

Beilstein J. Org. Chem. 2011, 7, 615–621, doi:10.3762/bjoc.7.72

• disadvantageous effect on complexation. It is remarkable that considerably higher yields were obtained when regioisomeric complexes 4 were prepared via the same protocol. The formation of boronate complex 8 was indicated by its 11B NMR shift value of 6.6 ppm [21] and confirmed by X-ray crystal structure analysis

Synthesis of chiral mono(N-heterocyclic carbene) palladium and gold complexes with a 1,1'-biphenyl scaffold and their applications in catalysis

• Lian-jun Liu,
• Feijun Wang,
• Wenfeng Wang,
• Mei-xin Zhao and
• Min Shi

Beilstein J. Org. Chem. 2011, 7, 555–564, doi:10.3762/bjoc.7.64

• '-biphenyl backbone have been prepared from chiral 6,6'-dimethoxybiphenyl-2,2'-diamine. The complexes were characterized by X-ray crystal structure diffraction. The Pd(II) complex showed good catalytic activities in the Suzuki–Miyaura and Heck–Mizoroki coupling reactions, and the (S)-Au(I) complexes also

• solution of DCM/pentane (1:3) was suitable for X-ray crystal structure analysis. (S)-6a: white solid; mp: 184.3–129.6 °C; [α]D20 +5.0 (c 0.25, CHCl3); IR (DCM) ν 3407, 2929, 2835, 1697, 1591, 1468, 1438, 1286, 1083, 1002, 852, 779, 747, 657 cm−1; 1H NMR (400 MHz, CDCl3, TMS): δ 2.19 (s, CH3, 3H), 3.21 (s

• reduced pressure and the residue purified by a silica gel flash column chromatography (eluent: petroleum ether/ethyl acetate, 2:1–0:1) to give 7 as a mixture of two isomers (117.0 mg, 70%). A single crystal grown from racemic complex 7 in a saturated solution of DCM:pentane (1/3) was suitable for X-ray

Anion–π interactions influence pK_a values

• Christopher J. Cadman and
• Anna K. Croft

Beilstein J. Org. Chem. 2011, 7, 320–328, doi:10.3762/bjoc.7.42

• )-1-naphthol derivative 4 was also crystallised and an X-ray crystal structure obtained, confirming the structure (Figure 2). Details are supplied in the Supporting Information Files 4–6. The acid dissociation constants (Ka'), and hence the pKa' values of each of the five derivatives 1–5, were

• corroborated in the solid state by the X-ray crystal structure of compound 4, which shows the structure as having the substituted aromatic ring roughly perpendicular to the naphthalene rings. These factors render the structures 1–5 suitable for the current study. Compounds 1–5 were titrated with TBAH to

Formation of macrocyclic lactones in the Paternò–Büchi dimerization reaction

• Junya Arimura,
• Tsutomu Mizuta,
• Yoshikazu Hiraga and
• Manabu Abe

Beilstein J. Org. Chem. 2011, 7, 265–269, doi:10.3762/bjoc.7.35

• 359.07391. X-ray crystal structure of the macrocyclic lactone 2a. 1H NMR spectra (500 MHz) for (a) the photolysate of 1a after 4 h irradiation in degassed and dried C6D6 solution, (b) for isolated macrocyclic lactone 2a, and (c) for furan-2-carbaldehyde (3). Reaction of furan with triplet excited carbonyls

Reciprocal polyhedra and the Euler relationship: cage hydrocarbons, C_nH_n and closo-boranes [B_xH_x]²⁻

• Michael J. McGlinchey and
• Henning Hopf

Beilstein J. Org. Chem. 2011, 7, 222–233, doi:10.3762/bjoc.7.30

• the centers of adjacent faces of the octahedron are connected, they yield a cube and vice versa; this is beautifully illustrated by the X-ray crystal structure of the [Mo6Cl8]4+ cluster in which an octahedron of molybdenum atoms is encapsulated within a cube of chlorines (Figure 2). The icosahedron

Olefin metathesis in nano-sized systems

• Didier Astruc,
• Abdou K. Diallo,
• Sylvain Gatard,
• Liyuan Liang,
• Cátia Ornelas,
• Victor Martinez,
• Denise Méry and
• Jaime Ruiz

Beilstein J. Org. Chem. 2011, 7, 94–103, doi:10.3762/bjoc.7.13

• steric congestion is also responsible for the decrease of the catalytic activity of Ru and Pd high-generation dendritic catalysts, even when these metallodendritic catalysts are soluble. The X-ray crystal structure of the model mononuclear complex in which the dendritic branch was replaced by a benzyl

Highly substituted benzannulated cyclooctanol derivatives by samarium diiodide-induced cyclizations

• Jakub Saadi,
• Irene Brüdgam and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, 1229–1245, doi:10.3762/bjoc.6.141

• unambiguously assigned by X-ray crystal structure (Figure 3) [51]. Assuming that the lactone bridge is formed only when carboxyl and hydroxyl groups are at the same face of the eight-membered ring, the configuration of 17a with the inverted phenyl-substituted stereocenter was assigned as the only alternative to

• relative configuration of compound 40, featuring a tetracyclic lactone-bridged core, were unambiguously determined by an X-ray crystal structure (Figure 5) [59]. The constitution of compound 39 was assigned as a cycloheptanol derivative based on the similarities of its 13C NMR data with those of 40 rather

Redox-active tetrathiafulvalene and dithiolene compounds derived from allylic 1,4-diol rearrangement products of disubstituted 1,3-dithiole derivatives

• Filipe Vilela,
• Peter J. Skabara,
• Christopher R. Mason,
• Thomas D. J. Westgate,
• Asun Luquin,
• Simon J. Coles and
• Michael B. Hursthouse

Beilstein J. Org. Chem. 2010, 6, 1002–1014, doi:10.3762/bjoc.6.113

• corresponding dihydrofuran. One possible explanation for this can be derived from the X-ray crystal structure of the dihydrofuran derivative [4]. The intramolecular close contacts between O(2)···S(2) and O(3)···S(3) arise from a three-centre four-electron interaction [15], which decreases the electron releasing