The preferred conformation of erythro- and threo-1,2-difluorocyclododecanes

• Yi Wang,
• Peer Kirsch,
• Tomas Lebl,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2012, 8, 1271–1278, doi:10.3762/bjoc.8.143

• revealed that the CF2 groups always occupied corner positions. This was deduced by a combination of 19F NMR, X-ray structure analysis and theory studies. Two reasons emerged for this. Firstly, if a C–F bond did project into the ring (endo), then the increased size of the fluorine atom relative to hydrogen

• location. Also the structure of conformer VII is almost identical to that obtained experimentally by X-ray structure analysis (Figure 4). It is not immediately obvious why threo 5b conformer VII is favoured (lower in energy) over conformer VI, although the energy difference is small (~0.7 kcal·mol−1). It

• ) isomers of 1,2-difluorocyclododecane were synthesised, and their preferred conformers were explored experimentally by 19F NMR, and X-ray structure analysis. A computational study was also carried out to establish favoured conformations and their relative ground-state energies. A particular focus of the

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• [100] and its application in liquid-crystal media and devices was again summarized in a Merck patent in 2004 [101]. In 2004 and 2005, Carella, Centore, and co-workers utilized 2-amino-4,5-dicyanoimidazole 83 (for X-ray structure analysis, see [102]) in the synthesis of chromophores 84–86 featuring

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

• Helen Jansen,
• J. Chris Slootweg and
• Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

• [10], has a boat-shaped conformation as determined by electron diffraction [11] and microwave studies of the parent [12] and by an X-ray structure analysis of the derivative thujic acid [13][14]. These methods gave inconsistent α and β tilt angles (see Scheme 2 for a description of the bow (α) and

• -benzophosphepine, 32) [7][102][103][104][105][106][107]. The single-crystal X-ray structure analysis of phenyl-substituted phosphepine 33 (Scheme 7) also showed a flattened-boat conformation (α = 40.5°, β = 28.2°) [5] compared to the metal-free parent structure (α = 48.3°, β = 27.8°), computed at the B3PW91/6-311

Photochemical and thermal intramolecular 1,3-dipolar cycloaddition reactions of new o-stilbene-methylene-3-sydnones and their synthesis

• Kristina Butković,
• Željko Marinić,
• Krešimir Molčanov,
• Biserka Kojić-Prodić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2011, 7, 1663–1670, doi:10.3762/bjoc.7.196

• which the expulsion of nitrogen is possible. The structure 14 (Scheme 6) was determined by additional NMR techniques, NOE and HMBC interactions, and by single crystal X-ray structure analysis (Figure 4) of the crystal formed in an NMR tube by slow evaporation of the solvent. Also, when compound 3b (cis

Single enantiomer synthesis of α-(trifluoromethyl)-β-lactam

• Václav Jurčík,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2011, 7, 759–766, doi:10.3762/bjoc.7.86

• . This novel β-lactam is a crystalline solid, and a suitable crystal was subjected to X-ray structure analysis. The structure of 1 is shown in Figure 2a. Accordingly, (S)-α-(p-methoxyphenyl)ethylamine (3b) emerged as the more satisfactory amine over 3a for the preparation of 1, due to the straightforward

• end, X-ray crystallography of the major diastereoisomers of 5a and 5b was attempted after chromatographic separation. Despite considerable effort however we could not obtain crystals of single isomers of 5a or 5b suitable for X-ray structure analysis. Thus, a preparation of 5c was carried out as

• solved by X-ray structure analysis. Comparison of the 1H NMR data of Hb and Hc of the diastereoisomers of 5a–c. Comparison of the 19F NMR chemical shifts of the diastereoisomers of 5a–c. Acknowledgements We thank the European Research Council for an Advanced Investigator Grant.

Synthesis of 5-(2-methoxy-1-naphthyl)- and 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene as 2,2'-disubstituted 1,1'-binaphthyls via benzannulated enyne–allenes

• Yu-Hsuan Wang,
• Joshua F. Bailey,
• Jeffrey L. Petersen and
• Kung K. Wang

Beilstein J. Org. Chem. 2011, 7, 496–502, doi:10.3762/bjoc.7.58

• chloride produced a crystal for X-ray structure analysis. Although the weakly diffracting crystal limited the amount of observed data, the analysis of these data supports the structural assignment of 20b. 5-[2-(Methoxymethyl)-1-naphthyl]-10-(1,1-dimethylethyl)-11H-benzo[b]fluorene (20c). The same procedure

SbCl₃-catalyzed one-pot synthesis of 4,4′-diaminotriarylmethanes under solvent-free conditions: Synthesis, characterization, and DFT studies

• Ghasem Rezanejade Bardajee

Beilstein J. Org. Chem. 2011, 7, 135–144, doi:10.3762/bjoc.7.19

• similar compounds where the bond lengths are 137.8 and 140.0 pm [49]. Although there are some differences between our results and those from X-ray structure analysis of similar compounds, the optimized structural parameters are very close to the X-ray values and are good enough for further vibrational

Synthesis of spiroannulated and 3-arylated 1,2,4-trioxanes from mesitylol and methyl 4-hydroxytiglate by photooxygenation and peroxyacetalization

• Axel G. Griesbeck,
• Lars-Oliver Höinck and
• Jörg M. Neudörfl

Beilstein J. Org. Chem. 2010, 6, No. 61, doi:10.3762/bjoc.6.61

• from the reaction of monofunctional ketones with ß-hydroperoxy alcohols 4 and 7 are collected in Table 1. All trioxanes 5a–e derived from 4 were crystalline and could be analyzed by X-ray structure analysis (Figure 2). The bond lengths of the crucial O-O bond were similar in all cases with the

Preparation of pyridine-3,4-diols, their crystal packing and their use as precursors for palladium-catalyzed cross-coupling reactions

• Tilman Lechel,
• Irene Brüdgam and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 42, doi:10.3762/bjoc.6.42

• pyridine-3,4-diol derivatives. The coexistence of pyridindiol and pyridinone tautomers in the solid state was discovered by an X-ray structure analysis. It was shown that pyridine-3,4-diols could easily be converted into bis(perfluoroalkanesulfonates) which represent substrates for the construction of

Prins fluorination cyclisations: Preparation of 4-fluoro-pyran and -piperidine heterocycles

• Guillaume G. Launay,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2010, 6, No. 41, doi:10.3762/bjoc.6.41

• configuration of the major diastereoisomer, an X-ray structure analysis was carried out on the major diastereoisomer produced in the low temperature reaction between alcohol 3 and 4-nitrobenzaldehyde. The X-ray confirmed that the major diastereoisomer is syn-5a as shown in Figure 1. In order to elaborate one of

Novel loop-like aromatic compounds: a further step on the road to nanobelts and nanotubes

• Venkataramana Rajuri,
• Dariush Ajami,
• Gaston R. Schaller,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2010, 6, No. 30, doi:10.3762/bjoc.6.30

• unambiguously identified from NMR spectral data and crystal structure determination (Figure 3). The X-ray structure analysis of compound 5 confirms that of the two conceivable isomers with C2 5a and CS symmetry 5b, the latter was formed as the main product. On applying the Diels–Alder reaction to compounds 1

Three step synthesis of single diastereoisomers of the vicinal trifluoro motif

• Vincent A. Brunet,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2009, 5, No. 61, doi:10.3762/bjoc.5.61

• case of 4, epoxide 6b was obtained in 80% yield and in 97:3 dr. For 5, the resulting epoxide 7b was generated as the only observable diastereoisomer. Epoxide (2R,3R,4R)-7b was recrystallised from diethyl ether to afford a suitable crystal for X-ray structure analysis which confirmed its relative and

• and relative stereochemistry of the crystalline threo-isomer (2R,3S,4S)-7a was confirmed by X-ray structure analysis as shown in Figure 2. With a strategy to access both stereoisomeric series of the allylic alcohol epoxides A in place, the fluorination reactions were then explored. The fluorination of

• (Scheme 5). Instead the fluorinated tetrahydrofuran 14 was isolated as a crystalline product in 33% yield and its structure and stereochemistry were established by X-ray structure analysis (Scheme 5). This deviant reaction was surprising not only because there was no trace of the analogous cyclisation

Synthesis of phosphonate and phostone analogues of ribose-1-phosphates

• Pitak Nasomjai,
• David O'Hagan and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2009, 5, No. 37, doi:10.3762/bjoc.5.37

• of 23a and 23b with TMSBr and then TFA yielded the free phosphonic acids which were neutralised with cyclohexylamine [12] to generate the non-hygroscopic salts 8a, b and 9a, b which could be recrystallised from MeOH/acetone. X-Ray structure analysis of a suitable crystal of the fluoromethyl

Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties

• Harald Schmaderer,
• Mouchumi Bhuyan and
• Burkhard König

Beilstein J. Org. Chem. 2009, 5, No. 26, doi:10.3762/bjoc.5.26

• catalytic efficacy, flavin derivatives bearing a guanidinium ion as oxoanion binding site were prepared. Chromophore and substrate binding site are linked by a rigid Kemp’s acid structure. The molecular structure of the new flavins was confirmed by an X-ray structure analysis and their photocatalytic

• linked to the chromophore via a rigid Kemp’s acid spacer. The connectivity and expected relative geometry of 1 and of the carboxylic acids 6 and 9 was confirmed by X-ray structure analysis. Guanidinium cations are known to bind oxoanions, such as phosphates, via hydrogen bonds. Therefore a benefit to the

Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)

• Henning Hopf,
• Christian Beck,
• Jean-Pierre Desvergne,
• Henri Bouas-Laurent,
• Peter G. Jones and
• Ludger Ernst

Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20

• ). 9-(anthrylmethyl)triphenylphosphonium bromide was easily obtained from triphenylphosphine and 9-bromomethylanthracene. 2 X-ray structure analysis Single crystals suitable for X-ray structure determination were grown by slow evaporation of a solution of 2 (150 mg) in dichloromethane (10 mL) by

• expense of the starting material (see Supporting Information p S3). No melting point could be determined because the powder decomposes back to 2 on heating. The mass spectrum was found to be that of 2 (see Experimental). Single crystals suitable for X-ray structure analysis could not be obtained. Evidence

A facile synthesis and fungicidal activities of 2-(alkylamino)-5,6-dimethylthieno[2,3-d]pyrimidin- 4(3H)-ones

• Yang-Gen Hu,
• Ai-Hua Zheng,
• Xu-Zhi Ruan and
• Ming-Wu Ding

Beilstein J. Org. Chem. 2008, 4, No. 49, doi:10.3762/bjoc.4.49

• broad absorption and NCH2 at 3.38–3.31 ppm as a multiple absorption, which strongly suggests the existence of a NHCH2CH2CH2CH3 group in 8b. Furthermore a single crystal of 8c was obtained from a methylene dichloride solution of 8c and X-ray structure analysis verified again the proposed structure [15

Understanding the mechanism of Pd-catalyzed allylic substitution of the cyclic difluorinated carbonates

• Jun Xu,
• Xiao-Long Qiu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2008, 4, No. 18, doi:10.3762/bjoc.4.18

• the monopalladium complex 11, which was too unstable to be isolated (Scheme 4). Neither did substitution of PPh3 by dppe deliver our desired complex 12 but gave instead the palladium complex 13, whose structure was confirmed by X-ray structure analysis. In our opinion, the reason we failed to isolate

Aroylketene dithioacetal chemistry: facile synthesis of 4-aroyl- 3-methylsulfanyl- 2-tosylpyrroles from aroylketene dithioacetals and TosMIC

• H. Surya Prakash Rao and
• S. Sivakumar

Beilstein J. Org. Chem. 2007, 3, No. 31, doi:10.1186/1860-5397-3-31

• were separated from minor amount of the imidazole 4 contaminant by column chromatography. The structure of 3b was confirmed on the basis of the single crystal X-ray structure analysis (deposited with Cambridge Crystallographic Data Center (CCDC); deposition No. 628766). The structure of AKDTAs 1b-g

The vicinal difluoro motif: The synthesis and conformation of erythro- and threo- diastereoisomers of 1,2-difluorodiphenylethanes, 2,3-difluorosuccinic acids and their derivatives

• David O'Hagan,
• Henry S. Rzepa,
• Martin Schüler and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2006, 2, No. 19, doi:10.1186/1860-5397-2-19

• more challenging. Partial separation of threo-13 was achieved by means of preparative thin layer chromatography. The enriched diasteroisomeric mixture could be crystallised to purity and crystals suitable for X-ray structure analysis were obtained (Figure 1). In the solid state erythro-13 adopts a

• and a suitable crystal was used for X-ray structure analysis. The resultant structure is shown in Figure 2. The most obvious feature of this structure is the perhaps unexpected gauche relationship between the phenyl rings which places the fluorine atoms also gauche to each other. This superficially

The first salen- type ligands derived from 3',5'-diamino- 3',5'-dideoxythymidine and -dideoxyxylothymidine and their corresponding copper(II) complexes

• Daniel Koth,
• Michael Gottschaldt,
• Helmar Görls and
• Karolin Pohle

Beilstein J. Org. Chem. 2006, 2, No. 17, doi:10.1186/1860-5397-2-17

• ',5'-bis(3,5-di-tert-butylsalicylaldiminato)-3',5'-dideoxyxylothymidine-copper(II) could be determined by single crystal X-ray structure analysis. The copper centre in this complex has distorted tetrahedral coordination geometry. Conclusion For the synthesis of 3',5'-diamino-3',5'-dideoxy thymidines

• formed uncharged stable copper(II) complexes with double deprotonated ligands as MS experiments had shown. Recrystallization of complex 13 using DMF resulted in crystals suitable for single crystal X-ray structure analysis [15] (For details see also: Figure 1 and Supporting Information File 1). The

Stereoselective α-fluoroamide and α-fluoro- γ-lactone synthesis by an asymmetric zwitterionic aza-Claisen rearrangement

• Kenny Tenza,
• Julian S. Northen,
• David O'Hagan and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2005, 1, No. 13, doi:10.1186/1860-5397-1-13

• zwitterionic aza-Claisen products, amide 25 was converted to a crystalline derivative for X-ray structure analysis. Treatment of 25 with LiAlH4 generated amine 27 which upon HCl-etherate treatment afforded the hydrochloride salt 28 (Scheme 7). The X-ray structure (Figure 1) established the absolute

• with (S)-N-allyl-2(methoxymethyl)pyrrolidine 23. Product α-fluoroamides were prepared with very high diastereoselectivities (99%de) and the absolute stereochemistry of these products was determined by derivatisation and X-ray structure analysis. It is notable that with this auxilary the fluorine