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

• the sterically shielded 2,7-di-tert-butylthiepine (17) (Figure 2), a relatively simple and thermally stable thiepine was obtained, allowing experimental studies of its chemical and physical properties [75]. A single-crystal X-ray analysis showed 17 to be less curved (α = 49.6° and β = 28.0°) [70] than

Bromine–lithium exchange: An efficient tool in the modular construction of biaryl ligands

• Laurence Bonnafoux,
• Frédéric R. Leroux and
• Françoise Colobert

Beilstein J. Org. Chem. 2011, 7, 1278–1287, doi:10.3762/bjoc.7.148

• °C, followed by trapping with ClPCy2, the corresponding monophosphine 7 was obtained in a good yield of 63%. The second Br–Li exchange was performed in toluene at 0 °C, affording ligand 6c in a moderate yield of 44% after trapping with ClPCy2 (Scheme 5). Single crystal X-ray analysis of 6c was

• for a PhD grant for L.B. We also thank Dr. Lydia Brelot, Université de Strasbourg, for single crystal X-ray analysis.

Use of mixed Li/K metal TMP amide (LiNK chemistry) for the synthesis of [2.2]metacyclophanes

• Marco Blangetti,
• Patricia Fleming and
• Donal F. O'Shea

Beilstein J. Org. Chem. 2011, 7, 1249–1254, doi:10.3762/bjoc.7.145

• at the C(4) position after metacyclophane synthesis [27][28]. The resolution of 8f by salt formation with (+)-1-phenylethylamine [27] has previously been accomplished. The stepwise anti conformation of the metacyclophane 8c was confirmed by single crystal X-ray analysis. Cyclophane 8c crystallised by

Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

• Henning Hopf,
• Vitaly Raev and
• Peter G. Jones

Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78

• -crystal X-ray analysis (Figure 4 and Figure 5); no other products could be detected. As for molecules 13 and 15, but to a slightly lesser extent, the newly formed bridges C17–22 in 23 and 24 are significantly longer than a standard single bond at 1.612(2) and 1.614(2) Å, respectively. On the other side of

• X-ray analysis (Figure 2). Molecules of 13 and 15 show common structural features. Despite the introduction of the new bridge C17–C24, the form of the original [2.2]paracyclophane is maintained to a considerable extent, with a flattened boat conformation of both six-membered rings (C4,5,7,8 and

• ethanol led to a mixture of 14 and the cyclooctadiene derivative 15, which was separable by column chromatography. The divinylcyclobutane derivative 14 was completely converted into the cyclooctadiene derivative 15 within half an hour in boiling ethanol. The structure of 15 was confirmed by single-crystal

Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan

• Benjamin Cao,
• Jonathan M. White and
• Spencer J. Williams

Beilstein J. Org. Chem. 2011, 7, 369–377, doi:10.3762/bjoc.7.47

• and H2 [40]. Unambiguous stereochemical assignment of (7S)-18 was achieved by single crystal X-ray analysis as shown in Figure 3, and is consistent with stereoselective delivery of hydride to the exo-face of the intermediate dioxolenium ion. Acetolysis of the benzylidene acetal 18 using 2% H2SO4/Ac2O

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

• Benan Kilbas and
• Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

• sensitized photooxygenation of the cycloheptatriene derivative 5a5b at room temperature resulted exclusively in the formation of the norcarene endoperoxide 6 [14][17]. The exact configuration of the endoperoxide 6 was determined by the single crystal X-ray analysis of the bisepoxide formed by the thermolysis

Oxalyl retro-peptide gelators. Synthesis, gelation properties and stereochemical effects

• Janja Makarević,
• Milan Jokić,
• Leo Frkanec,
• Vesna Čaplar,
• Nataša Šijaković Vujičić and
• Mladen Žinić

Beilstein J. Org. Chem. 2010, 6, 945–959, doi:10.3762/bjoc.6.106

• arrangements of i-Bu groups occur (Figure 10b, Newman projections of two stereogenic centers only). Our earlier results based on single crystal X-ray analysis of bis(amino acid)oxalamides showed that their most stable conformations are characterized by vicinal positioning of the methine proton at the

Synthesis of oxa-bridged derivatives from Diels–Alder bis-adducts of butadiene and 1,2,3,4-tetrahalo-5,5-dimethoxycyclopentadiene

• Faiz Ahmed Khan and
• Karuppasamy Parasuraman

Beilstein J. Org. Chem. 2010, 6, No. 64, doi:10.3762/bjoc.6.64

• reaction was carried out in presence of the phase transfer catalyst TBHSO4 the bis-oxa-bridged compounds 8 and 10 were obtained (after esterification with diazomethane) in 31 and 37%, respectively (Scheme 3). The relative stereochemistry in 8 was unambiguously established by the single crystal X-ray

• analysis (Figure 1) [20]. Working backwards, the structures of the adduct 5, the bis-diketone 7 were confirmed unequivocally. We next turned our attention to the bromo analogue 1b in order to see if the overall yield of the bis-oxa-bridged derivatives 8 and 10 could be improved. We were also interested to

The efficient synthesis of dibenzo[d,d′]benzo[1,2-b:4,3-b′]dithiophene and cyclopenta[1,2-b:4,3-b′]bis(benzo[d]thiophen)-6-one

• Zhihua Wang,
• Sheng Zhu,
• Jianwu Shi and
• Hua Wang

Beilstein J. Org. Chem. 2009, 5, No. 55, doi:10.3762/bjoc.5.55

• slow evaporation of a solution of 1 in CHCl3/CH3OH (5/1, v/v). The crystal structure of 1 was confirmed by single-crystal X-ray analysis (Figure 2 and Figure 3). 1 has non-planar π-extended frameworks, and its molecule is compressed and dominated by a helical structure (Figure 2). The distance between

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

Shape- persistent macrocycle with intraannular alkyl groups: some structural limits of discotic liquid crystals with an inverted structure

• Sigurd Höger,
• Jill Weber,
• Andreas Leppert and
• Volker Enkelmann

Beilstein J. Org. Chem. 2008, 4, No. 1, doi:10.1186/1860-5397-4-1

• to cross the rings and to fill their interior completely. The investigation of the thermal behavior has shown that the smaller cycles do not exhibit thermotropic mesophases. Single crystal x-ray analysis indicates that the anisotropy in these compounds is too small to describe them as plates rather

• fill their interior. The investigation of the thermal behavior has shown that the smaller cycles do not exhibit thermotropic mesophases. Although single crystal x-ray analysis has proven that these compounds fulfill in principle our previously described design principle for discotics with an inverted

Synthesis of crispine A analogues via an intramolecular Schmidt reaction

• Ajoy Kapat,
• Ponminor Senthil Kumar and
• Sundarababu Baskaran

Beilstein J. Org. Chem. 2007, 3, No. 49, doi:10.1186/1860-5397-3-49

• derivative 3 was established by 1D and 2D NMR analyses which was unambiguously further confirmed by single crystal X-ray analysis (Figure 1), on the corresponding acid derivative 4 (Scheme 9). After achieving the construction of the indolizidine skeleton using the intramolecular Schmidt reaction, our next

• indolizidine derivative 3 was unambiguously confirmed by single crystal X-ray analysis. Interestingly, an unusual cleavage of ethylene ketal to vinylether was observed during the alkylation of ketal-ester 12. Since the compounds 5 and 16 are highly functionalized intermediates, they can be further exploited in

Diastereoselective synthesis of some novel benzopyranopyridine derivatives

• Pradeep K. Mohakhud,
• Sujeet M. R. Kumar,
• Vasanth M. R. Kumar,
• Ravi M. R. Kumar,
• Moses D. R. Babu,
• Vyas D. R. K and
• Om D. R. Reddy

Beilstein J. Org. Chem. 2006, 2, No. 25, doi:10.1186/1860-5397-2-25

• enantiomers 7a and 7b. The absolute configuration is determined by single crystal X-ray analysis of the mandelate salt. General structures A & B, Tetrahydro cannabinole derivatives. General structures C & D, Benzopyrano pyridine derivatives. Proposed mechanism of tetrahydropyridine formation, Proposed