On the mechanism of action of gated molecular baskets: The synchronicity of the revolving motion of gates and in/out trafficking of guests

• Keith Hermann,
• Stephen Rieth,
• Hashem A. Taha,
• Bao-Yu Wang,
• Christopher M. Hadad and
• Jovica D. Badjić

Beilstein J. Org. Chem. 2012, 8, 90–99, doi:10.3762/bjoc.8.9

• rise to two enantiomeric conformers 1A and 1B (Figure 7A). The interconversion kinetics of the 1A/B racemization can be followed by dynamic NMR spectroscopy in which a singlet corresponding to Ha/Hb nuclei at high temperatures is seen to split into two doublets at low temperatures. In particular, the

• reality, when the internal hydrogen bonds are broken and the gates open up the guest does not have to depart the basket cavity. That is to say, the gates should be able to revolve to allow the interconversion of 1A–CH3CCl3 into 1B–CH3CCl3 without even ejecting the guest. Accordingly, we hereby propose

• – distances during SMD simulation with CH3CCl3 being pulled on the side. (A) The interconversion of conformational enantiomers 1A and 1B, having anticlockwise and clockwise senses in the orientation of the intramolecular N–H…N hydrogen bonds, contributes to the process of racemization, i.e., the opening and

On the control of secondary carbanion structure utilising ligand effects during directed metallation

• Andrew E. H. Wheatley,
• Jonathan Clayden,
• Ian H. Hillier,
• Alison Campbell Smith,
• Mark A. Vincent,
• Laurence J. Taylor and
• Joanna Haywood

Beilstein J. Org. Chem. 2012, 8, 50–60, doi:10.3762/bjoc.8.5

• respect to the lithium ion in solution, potentially leading to the interconversion of different solution structures. Synthetic work will focus on employing the reported lateral metallates synthetically using a range of electrophiles. Of major interest will be the study of how steric encumbrance controls

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

• -triene [14]. Besides the 1–2 interconversion, the C7H8 system is rich in rearrangements (Scheme 3). In 1957, Woods found that bicyclo[2.2.1]hepta-2,5-diene (12) converts to cycloheptatriene (1), which was postulated to proceed via diradical 11 and norcaradiene (2) [28]. Instead, pyrolysis of 1 yielded

• norcaradienes, and the barriers for their interconversion and ring inversion. Although the boat form prevails for the monocyclic heteropines 1, 3 and 5, Cremer et al. showed that this represents an incomplete picture [43][44]. In fact, they are “perturbed” boats with at least 22% chair character, leading to an

• ]. The calculated barrier of 8.3 kcal·mol−1 for thiepine (5) is nearly twice as large, possibly due to the higher antiaromatic destabilization of the flattened thiepine ring [40], but the interconversion of the boat forms of azepine and phosphepine are about equally favourable, requiring 3.0 [41] and 5.2

Directed aromatic functionalization in natural-product synthesis: Fredericamycin A, nothapodytine B, and topopyrones B and D

• Charles Dylan Turner and
• Marco A. Ciufolini

Beilstein J. Org. Chem. 2011, 7, 1475–1485, doi:10.3762/bjoc.7.171

• . This was due in part to undesired base-promoted reactions of the enolizable ketone segments, but also to the slow rate of interconversion of 47 and 48 (only the former can produce the desired pyridone). Experiment revealed that it was best to carry out the Michael step with DBU in pyridine, followed by

Continuous gas/liquid–liquid/liquid flow synthesis of 4-fluoropyrazole derivatives by selective direct fluorination

• Jessica R. Breen,
• Graham Sandford,
• Dmitrii S. Yufit,
• Judith A. K. Howard,
• Jonathan Fray and
• Bhairavi Patel

Beilstein J. Org. Chem. 2011, 7, 1048–1054, doi:10.3762/bjoc.7.120

• required to exploit fully the use of fluorinated systems in life science applications. In general, there are two complimentary approaches to the synthesis of fluoroorganic products [5][6], which involve either carbon–fluorine bond formation, requiring functional group interconversion utilising an

Isotopic labelling studies for a gold-catalysed skeletal rearrangement of alkynyl aziridines

• Paul W. Davies,
• Nicolas Martin and
• Neil Spencer

Beilstein J. Org. Chem. 2011, 7, 839–846, doi:10.3762/bjoc.7.96

• indentified from the reaction mixture. Though H/D exchange in pyrroles has been noted in gold-catalysed reactions [13], control reactions had shown that no H/D exchange occurred in this specific system [18][19]. There was also no interconversion between 2,4- and 2,5-isomers under the same reaction conditions

• stabilising B. The substrates were prepared by Sonogashira reaction between propargyl alcohol and the appropriately substituted iodobenzene substrate 22, 23 (Scheme 12). Functional group interconversion of the alcohols by bromination and substitution results in the sulfonium salts 28, 29 which were reacted

Synthesis of Ru alkylidene complexes

• Renat Kadyrov and
• Anna Rosiak

Beilstein J. Org. Chem. 2011, 7, 104–110, doi:10.3762/bjoc.7.14

• interconversion. Supporting Information File 10: Detailed experimental data.

Stereoselectivity of supported alkene metathesis catalysts: a goal and a tool to characterize active sites

• Christophe Copéret

Beilstein J. Org. Chem. 2011, 7, 13–21, doi:10.3762/bjoc.7.3

• generate a metallacyclobutane from which a new alkylidene and alkene with specific configurations will be formed. Note that additional steps are possible such as: i) formation of the active alkylidene species or ii) interconversion of metallacyclobutane isomers (TBP vs SBP), however, these typically do not

Intramolecular hydroxycarbene C–H-insertion: The curious case of (o-methoxyphenyl)hydroxycarbene

• Dennis Gerbig,
• David Ley,
• Hans Peter Reisenauer and
• Peter R. Schreiner

Beilstein J. Org. Chem. 2010, 6, 1061–1069, doi:10.3762/bjoc.6.121

• and kinetics grounds, the direct interconversion of 7 and 8 can therefore be excluded. Computational considerations AE-CCSD(T)/cc-pVDZ single point computations (with DFT ZPVEs; Scheme 8, for computational details see Computational Methods below) on M06-2X/cc-pVDZ geometries do not indicate a

[3.3]Dithia-bridged cyclophanes featuring a thienothiophene ring: synthesis, structures and conformational analysis

• Sabir H. Mashraqui,
• Yogesh Sanghvikar,
• Shailesh Ghadhigaonkar,
• Sukeerthi Kumar,
• Auke Meetsma and
• Elise Trân Huu Dâu

Beilstein J. Org. Chem. 2009, 5, No. 74, doi:10.3762/bjoc.5.74

• in 9 and 11 would convert separate signals for the phenyl ring and methoxyl protons into singlets due to the fast interconversion of ring conformers. Accordingly, we recorded variable temperature NMR spectra of dithia-cyclophanes 7, 9 and 11 at different intervals from room temperature to 130 °C in

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• installed the three carbon chain on the newly formed para-methoxyphenol which was subsequently oxidized to the quinone then reduced to yield the corresponding para-catechol. This latter compound was protected with benzyl groups. Although this sequence of protecting group interconversion required many steps

Highly brominated anthracenes as precursors for the convenient synthesis of 2,9,10-trisubstituted anthracene derivatives

• Osman Cakmak,
• Leyla Aydogan,
• Kiymet Berkil,
• Ilhami Gulcin and
• Orhan Buyukgungor

Beilstein J. Org. Chem. 2008, 4, No. 50, doi:10.3762/bjoc.4.50

• ). The configurational isomerization stopped in the dark, which strongly supports a radical mechanism for interconversion of the bromides. We assume that the visible light initiates formation of radicals at C-1 and C-3 positions (Scheme 2), while recombination of the radicals (9 and 10) causes

Asymmetric synthesis of biaryl atropisomers by dynamic resolution on condensation of biaryl aldehydes with (−)-ephedrine or a proline- derived diamine

• Ann Bracegirdle,
• Jonathan Clayden and
• Lai Wah Lai

Beilstein J. Org. Chem. 2008, 4, No. 47, doi:10.3762/bjoc.4.47

• thermodynamically controlled interconversion of the atropisomeric diastereoisomers of 9 and 10. It seems probable however that the varying selectivities at lower temperatures are the result of a complex interplay between the kinetic and thermodynamic factors. Preparative dynamic resolutions We decided to pursue

• may attain thermodynamic equilibrium if an alternative mechanism for their interconversion presents itself, namely hydrolysis back to the aldehyde 6 (or maybe the hemiaminal 12). P-9 is more stable than M-9, and equilibration allows the ratio of P:M-9 to build up to about 5:1. High selectivity is

• interconversion of the atropisomeric products and allows thermodynamic equilibrium to be attained. The imidazolidine products may be hydrolysed and reduced to atropisomeric alcohols in moderate yield and with excellent enantioselectivity. Experimental For general experimental procedures, see Supporting

Synthesis of deep- cavity fluorous calix[4]arenes as molecular recognition scaffolds

• Maksim Osipov,
• Qianli Chu,
• Steven J. Geib,
• Dennis P. Curran and
• Stephen G. Weber

Beilstein J. Org. Chem. 2008, 4, No. 36, doi:10.3762/bjoc.4.36

• conformations: cone (Figure 1), partial cone, 1,2, and 1,3 alternates [1]. Although small groups (Me, Et) on the lower rim allow for interconversion between conformers, large groups prevent interconversion [12]. Reactions that lock the conformation result in a mixture of conformers; however, methods exist to

Trifluoromethyl ethers – synthesis and properties of an unusual substituent

• Frédéric R. Leroux,
• Baptiste Manteau,
• Jean-Pierre Vors and
• Sergiy Pazenok

Beilstein J. Org. Chem. 2008, 4, No. 13, doi:10.3762/bjoc.4.13

• aromatics is based on the synthesis-oriented organometallic chemistry. The metal is introduced into a substrate in general by either one of two favorite methods, the permutational interconversion of halogen against metal or hydrogen against metal and subsequently replaced by an electrophile [69][70]. The

Synthesis of (–)-Indolizidine 167B based on domino hydroformylation/cyclization reactions

• Giuditta Guazzelli,
• Raffaello Lazzaroni and
• Roberta Settambolo

Beilstein J. Org. Chem. 2008, 4, No. 2, doi:10.1186/1860-5397-4-2

• describe here a new synthesis of optically active (–)-Indolizidine 167B based on regioselective hydroformylation/intramolecular cyclization reactions which provides a general approach to the indolizine nucleus. It is a multi-step domino process which starts with the interconversion of the isomeric rhodium

• under H2 50 atm, after CO and H2 removal, 80% yield; iii 10 atm H2, Rh/C (5%), r.t. 45 min, 75% yield; iv H2 10 atm, Rh/C (5%), r.t., 60 min, 64% yield. Stereospecific interconversion of the rhodium-alkyl intermediates as the key for regioselective formation of the linear aldehyde 2a. Supporting