Particularly strong C-H...pi interactions between benzene and all-cis 1,2,3,4,5,6-hexafluorocyclohexane

The authors thank EaStCHEM and the University of St Andrews for access to a computing facility managed by Dr H. Fruchtl, CNPq and FAPESP for the studentship for R.A.C. (#2011/01170-1, FAPESP) and for financial support (#2014/25903-6), as well as CNPq for the fellowship for R.R. DO’H thanks the Royal Society for a Wolfson Research Merit Award.We present the first high-level ab initio benchmark study of the interaction energy between fluorocyclohexanes and benzene. These compounds form CH...pi interactions with aromatic solvents which causes notable shielding of the axial cyclohexane protons. For the recently synthesised all-cis 1,2,3,4,5,6-hexafluorocyclohexane the interaction energy with benzene amounts to -7.9 kcal/mol and -6.4 kcal/mol at the MP2 and SCS-MP2 levels, respectively (extrapolated to the complete basis set limit), which according to dispersion-corrected density functional calculations, is largely due to dispersion.PostprintPeer reviewe

Thermal rearrangement of thiocarbonyl-stabilised triphenylphosphonium ylides leading to (Z)-1-diphenylphosphino-2-(phenylsulfenyl)alkenes and their coordination chemistry

While thiocarbonyl-stabilised phosphonium ylides generally react upon flash vacuum pyrolysis by extrusion of Ph3PS to give alkynes in an analogous way to their carbonyl-stabilised analogues, two examples with a hydrogen atom on the ylidic carbon are found to undergo a quite different process. The net transfer of a phenyl group from P to S gives (Z)-configured 1-diphenylphosphino-2-(phenylsulfenyl)alkenes in a novel isomerisation process via intermediate λ5-1,2-thiaphosphetes. These prove to be versatile hemilabile ligands with a total of seven complexes prepared involving five different transition metals. Four of these have been characterised by X-ray diffraction with two involving the bidentate ligand forming a five-membered ring metallacycle and two with the ligand coordinating to the metal only through phosphorus.Publisher PDFPeer reviewe

Janus face aspect of all-cis 1,2,3,4,5,6-hexafluorocyclohexane dictates remarkable anion and cation interactions in the gas phase

The authors acknowledge support in the form of NSERC (Canada) Discovery Grants to EF, WSH, and TBM and an EPSRC (UK) responsive mode grant to DO’H and NSK is gratefully acknowledged.Experiments have been carried out in which electrospray ionization has been used to generate ionic complexes of all-cis 1,2,3,4,5,6 hexafluorocyclohexane. These complexes were subsequently mass isolated in a quadrupole ion trap mass spectrometer and then irradiated by the tunable infrared output of a free electron laser in the 800-1600 cm−1 range. From the frequency dependence of the fragmentation of the complexes, vibrational signatures of the complexes were obtained. Computational work carried out in parallel reveals that the complexes formed are very strongly bound and are among the most strongly bound complexes of Na+ and Cl− ever observed with molecular species. The dipole moment calculated for the heaxafluorocyclohexane is very large (~7 D) and it appears that the bonding in each of the complexes has a significant electrostatic contribution.PostprintPeer reviewe

Simple and inexpensive method for the detection of carbon monoxide released from thermal cheletropic decarbonylation reactions

This work presents a simple protocol that demonstrates the use of an inexpensive household carbon monoxide detector as a useful tool to detect the release of carbon monoxide gas from thermal cheletropic decarbonylation reactions. The carbon monoxide detection method described has been employed in a short series of reactions used in a university teaching laboratory setting, and full procedures for these are outlined. In each case, the procedure to isolate and identify the decarbonylation products has also been provided.PostprintPeer reviewe

The synthesis and biological evaluation of d-myo-inositol 1,4,5-trisphosphate receptor ligands

The intracellular second messenger InsP₃ is a vital molecule in the regulation of Ca²⁺ signalling. Ca²⁺ mediates a wide range of cellular activities from fertilisation and cell differentiation through to apoptoisis. Using X-ray crystal structure data and molecular modelling, a series of novel InsP₃ analogues were designed as selective InsP₃R-antagonists. Two novel synthetic routes have been developed for the synthesis of these analogues. The first route uses a Ferrier-II rearrangement to provide enantiopure inositol intermediates, whereas, the second route employs a diastereomeric resolution to obtain the enantiopure inositols. The successful synthesis of InsP₃ and a series of 5-position modified analogues are reported herein

Particularly strong C-H...pi interactions between benzene and all-cis 1,2,3,4,5,6-hexafluorocyclohexane

We present the first high-level ab initio benchmark study of the interaction energy between fluorocyclohexanes and benzene. These compounds form CH...pi interactions with aromatic solvents which causes notable shielding of the axial cyclohexane protons. For the recently synthesised all-cis 1,2,3,4,5,6-hexafluorocyclohexane the interaction energy with benzene amounts to -7.9 kcal/mol and -6.4 kcal/mol at the MP2 and SCS-MP2 levels, respectively (extrapolated to the complete basis set limit), which according to dispersion-corrected density functional calculations, is largely due to dispersion

All-<i>cis</i> 1,2,3,4,5,6-hexafluorocyclohexane is a facially polarized cyclohexane

The highest-energy stereoisomer of 1,2,3,4,5,6-hexafluorocyclohexane, in which all of the fluorines are ‘up’, is prepared in a 12-step protocol. The molecule adopts a classic chair conformation with alternate C–F bonds aligned triaxially, clustering three highly electronegative fluorine atoms in close proximity. This generates a cyclohexane with a high molecular dipole (μ = 6.2 D), unusual in an otherwise aliphatic compound. X-ray analysis indicates that the intramolecular Fax···Fax distances (∼2.77 Å) are longer than the vicinal Fax···Feq­ distances (∼2.73 Å) suggesting a tension stabilizing the chair conformation. In the solid state the molecules pack in an orientation consistent with electrostatic ordering. Our synthesis of this highest-energy isomer demonstrates the properties that accompany the placement of axial fluorines on a cyclohexane and the unusual property of a facially polarized ring in organic chemistry. Derivatives have potential as new motifs for the design of functional organic molecules or for applications in supramolecular chemistry design.</p

3,5-Dithiatricyclo[5.2.1.02,6]decan-2-one (dataset)

CCDC 198978

Thermal rearrangement of thiocarbonyl-stabilised triphenylphosphonium ylides leading to (Z)-1-diphenylphosphino-2-phenylsulfenylalkenes

While thermolysis of thiocarbonyl-stabilised phosphonium ylides generally results in extrusion of Ph3PS to give alkynes, those with a P=CH function instead undergo a novel P to S transfer of a phenyl group to give (Z)-configured 1-phosphino-2-sulfenyl-alkenes of interest as bidentate ligands.</p

Thermal rearrangement of thiocarbonyl-stabilised triphenylphosphonium ylides leading to (Z)-1-diphenylphosphino-2-phenylsulfenylalkenes

While thermolysis of thiocarbonyl-stabilised phosphonium ylides generally results in extrusion of Ph3PS to give alkynes, those with a P=CH function instead undergo a novel P to S transfer of a phenyl group to give (Z)-configured 1-phosphino-2-sulfenyl-alkenes of interest as bidentate ligands.</p