Bedmap3 updated ice bed, surface and thickness gridded datasets for Antarctica.

We present Bedmap3, the latest suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60 °S. Bedmap3 incorporates and adds to all post-1950s datasets previously used for Bedmap2, including 84 new aero-geophysical surveys by 15 data providers, an additional 52 million data points and 1.9 million line-kilometres of measurement.

The low-lying electronic states of 4H-pyran-4-thione; a photoionization and vacuum ultraviolet absorption study, with interpretation by configuration interaction and density functional calculations for the ionic and singlet states.

Two synchrotron-based studies on 4H-pyran-4-thione, photoelectron spectroscopy and vacuum ultraviolet (VUV) absorption spectra were performed. A highly resolved structure was observed in the photoelectron spectrum (PES), in contrast to an earlier PES study, where little structure was observed. The sequence of ionic states was determined using configuration interaction and coupled cluster methods.

Application of the Wittig Rearrangement of -Butyl-2-benzyloxybenzamides to Synthesis of Phthalide Natural Products and 3-Aryl-3-benzyloxyisoindolinone Anticancer Agents.

Application of the [1,2]-Wittig rearrangement and cyclisation approach to 3-arylphthalides has been evaluated for the synthesis of three bioactive natural products. While this is successful in the case of crycolide, providing the second synthesis of this compound, the more sterically demanding targets isopestacin and cryphonectric acid prove not to be amenable to this approach, with the 2,6-disubstituted aryl groups causing the failure of the rearrangement and alkylation steps, respectively. Direct oxidation of the substituted benzhydrols resulting from [1,2]-Wittig rearrangement using MnO provides a new route to 3-aryl-3-hydroxyisoindolinones, and this method has been used in the synthesis of two 3-aryl-3-benzyloxyisoindolinone anticancer agents.

The ultraviolet and vacuum ultraviolet absorption spectrum of gamma-pyrone; the singlet states studied by configuration interaction and density functional calculations.

A synchrotron based vacuum ultraviolet absorption spectrum for γ-pyrone has been interpreted in terms of singlet excited electronic states using a variety of coupled cluster, configuration interaction, and density functional calculations. The extremely weak spectral onset at 3.557 eV shows eight vibrational peaks, which following previous analyses, are attributed to a forbidden 1A2 state.

Thermal Rearrangement of Thiocarbonyl-Stabilised Triphenylphosphonium Ylides Leading to ()-1-Diphenylphosphino-2-(phenylsulfenyl)alkenes and Their Coordination Chemistry.

While thiocarbonyl-stabilised phosphonium ylides generally react upon flash vacuum pyrolysis by the extrusion of PhPS 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 ()-configured 1-diphenylphosphino-2-(phenylsulfenyl)alkenes in a novel isomerisation process via intermediate λ-1,2-thiaphosphetes. These prove to be versatile hemilabile ligands with a total of seven complexes prepared involving five different transition metals.

New Chemistry of Chiral 1,3-Dioxolan-4-Ones.

(2,5)-5-Phenyl-2--butyl-1,3-dioxolan-4-one, readily derived from mandelic acid, undergoes the Michael addition to butenolide and 4-methoxy-β-nitrostyrene with the absolute configuration of the products confirmed by X-ray diffraction in each case. In the former case, thermal fragmentation gives the phenyl ketone, thus illustrating use of the dioxolanone as a chiral benzoyl anion equivalent. The Diels-Alder cycloaddition chemistry of (2)-5-methylene-2--butyl-1,3-dioxolan-4-one, derived from lactic acid, has been further examined with the X-ray structures of four adducts determined.

The ionic and ground states of gamma-pyrone. The photoionization spectrum studied by synchrotron radiation and interpreted by configuration interaction and density functional calculations.

A synchrotron-based photoionization spectrum up to 27 eV represents a considerable improvement in resolution over early He(I) and He(II) spectra. Symmetry-adapted coupled cluster calculations of the ionic state sequence give the sequence of state vertical ionization energies (VIE) as 1B < 1B < 1A < 2B < 1A. Generally, these symmetry-adapted cluster configuration interactions VIE match reasonably well with the experimental spectrum over this wide energy range.

The excited states of azulene: A study of the vibrational energy levels for the lower ππ*-valence states by configuration interaction and density functional calculations, and theoretical studies of the Rydberg states.

A new vacuum ultraviolet absorption (VUV) spectrum of azulene vapor has been obtained by using a synchrotron radiation source. The onset of the ultraviolet spectrum, previously reported by Sidman et al., has been analyzed in detail by Franck-Condon (FC) and Herzberg-Teller (HT) methods.

Further Studies on the [1,2]-Wittig Rearrangement of 2-(2-Benzyloxy)aryloxazolines.

The behaviour of 14 ortho-functionalised 2-aryloxazolines (11 of them prepared and characterised for the first time) with butyllithium has been examined. Significant limitations to the Wittig rearrangement of such systems are revealed. In terms of asymmetric Wittig rearrangement, good diastereoselectivity is obtained with a valine-derived 4-isopropyl oxazoline, but this is compromised by racemisation upon hydrolysis.

Access to Diarylmethanols by Wittig Rearrangement of , , and Benzyloxy--Butylbenzamides.

The -butyl amide group, CONHBu, has been found to be an effective promoter of the [1,2]-Wittig rearrangement of aryl benzyl ethers and thus allow the two-step synthesis of isomerically pure substituted diarylmethanols starting from simple hydroxybenzoic acid derivatives. The method is compatible with a wide range of functional groups including methyl, methoxy, and fluoro, although not with nitro and, unexpectedly, is applicable to as well as and isomeric series.

The ground and ionized states of azulene: A combined study of the vibrational energy levels by photoionization, configuration interaction, and density functional calculations.

A synchrotron-based photoionization spectrum of azulene shows a significant additional vibrational fine structure when compared to previous studies. This spectrum was successfully analyzed by using Franck-Condon (FC) methods. Previously reported zero-kinetic-energy electron spectra for azulene have been reinterpreted in FC terms, leading to some alternative assignments to the earlier work.

Rationalisation of Patterns of Competing Reactivity by X-ray Structure Determination: Reaction of Isomeric (Benzyloxythienyl)oxazolines with a Base.

Three isomeric (benzyloxythienyl)oxazolines , and have been prepared and are found, upon treatment with a strong base, to undergo either Wittig rearrangement or intramolecular attack of the benzylic anion on the oxazoline function to give products derived from cleavage of the initially formed 3-aminothienofuran products. This pattern of reactivity is directly linked to the distance between the two reactive groups as determined by X-ray diffraction, with the greatest distance in leading to exclusive Wittig rearrangement, the shortest distance in giving exclusively cyclisation-derived products, and the intermediate distance in leading to both processes being observed. The corresponding -butyl amides were also obtained in two cases and one of these undergoes efficient Wittig rearrangement leading to a thieno[2,3-]pyrrolone product.

The vacuum ultraviolet absorption spectrum of norbornadiene: Vibrational analysis of the singlet and triplet valence states of norbornadiene by configuration interaction and density functional calculations.

A synchrotron-based vacuum ultraviolet (VUV) absorption spectrum of norbornadiene (NBD) is reported, and the extensive vibrational structure obtained has been analyzed. The previously known 5b3s-Rydberg state has been reinterpreted by comparison with our recent high-resolution photoelectron spectral analysis of the XB ionic state. Additional vibrational details in the region of this Rydberg state are observed in its VUV spectrum when compared with the photoelectron B ionic state; this is attributed to the underlying valence state structure in the VUV.

High-level studies of the ionic states of norbornadiene and quadricyclane, including analysis of new experimental photoelectron spectra by configuration interaction and coupled cluster calculations.

Synchrotron-based photoelectron spectra (PES) of norbornadiene (NBD) and quadricyclane (QC) differ significantly from those in previous studies. The adiabatic ionization energy (AIE) for NBD, assigned to the B state at 8.279 eV, shows a progression of 18 members with decreasing vibration frequency from 390 cm to 340 cm; our calculated frequency is 381 cm.

The periodic table and other wallcharts in the teaching of chemistry in St Andrews, 1884-1919.

The teaching of the chemistry of the elements at the University of St Andrews by Professor Thomas Purdie FRS is examined with reference to selections from a collection of recently discovered historic wallcharts and extracts from his detailed hand-written lecture notes. Together these reveal a comprehensive and exciting programme of lectures incorporating numerous practical demonstrations which were continually updated to reflect the latest state of knowledge in what was a rapidly changing field. This article is part of the theme issue 'Mendeleev and the periodic table'.

The vacuum ultraviolet spectrum of cyclohepta-1, 3, 5-triene: Analysis of the singlet and triplet excited states by ab initio and density functional methods.

The vacuum ultraviolet (VUV) spectrum for cyclohepta-1,3,5-triene up to 10.8 eV shows several broad bands, which are compared with electron impact spectra. Local curve fitting exposed groups of sharp vibrational peaks, which are assigned to Rydberg states.

The ground and ionic states of cyclohepta-1,3,5-triene and their relationship to norcaradiene states: New H and C NMR spectra and analysis of a new experimental photoelectron spectrum by ab initio methods.

The strong inter-relationship between cyclohepta-1,3,5-triene (CHT) and norcaradiene (NCD) systems observed in some reactions has been extended to include the energy surfaces for some low-lying ionic states. Equilibrium structures for ionic states of CHT with A' symmetry were routinely found; the structures emerging with A'' symmetry were NCD ionic states. A detailed analysis of these surfaces as a function of the C to C distance showed that while minima occurred for both state symmetries, curve crossing occurs in C symmetry, which is avoided by distortion to C symmetry.

Gas-Phase Conversion of 1,3-Dithiolane-2-Thione Into 1,3-Dithiolan-2-One Over Molybdenum Trioxide.

Gas-phase reaction of 1,3-dithiolane-2-thione over molybdenum trioxide supported on pumice stone results in efficient conversion into 1,3-dithiolan-2-one. The solid reagent is regenerated on exposure to air and thus acts as a catalyst for the overall conversion of the thione and oxygen from the air into the ketone and sulfur dioxide. The process can be carried out under either dynamic vacuum or atmospheric pressure flow conditions and using a solid reagent prepared either by physical mixing of MoO with the support or by solution impregnation, with an isolated yield of up to 67% obtained.

Synthesis, microwave spectra, x-ray structure, and high-level theoretical calculations for formamidinium formate.

An efficient synthesis of formamidinium formate is described. The experimental x-ray structure shows both internal and external H-bonding to surrounding molecules. However, in the gas phase, this compound occurs as a doubly hydrogen bonded dimer between formamidine and formic acid.

Further Studies on the Pyrolytic Domino Cyclization of Stabilized Phosphonium Ylides Bearing an -Aminophenyl Group.

Four new, stabilized phosphonium ylides containing a 2-(benzyl(methyl)amino)phenyl group have been prepared and characterized and are found, upon pyrolysis under gas-phase flow conditions, to lose Ph₃PO and benzyl radicals to afford new heterocyclic products resulting from domino cyclization of both - and -centered radicals. Most products arise from processes of the former type and have quinoline, phenanthridine, or ring-fused phenanthridine structures, while in one case, a process of the latter type leads to a benzocarbazole product. The X-ray structure of a 2-(methyl(tosyl)amino)phenyl ylide is also reported.

The photoelectron spectra of the isomeric 1- and 2-methyltetrazoles; their equilibrium structures and vibrational analysis by ab initio calculations.

New synchrotron based studies of the photoelectron ionization spectra (PES) for the isomeric 1- and 2-methyltetrazoles (1- and 2-MeTet) show markedly higher resolution than previous reports. The unusual spectral profiles suggest that a considerable overlay of the ionic states occurs for both molecules. Under these circumstances of near degeneracy of two or more ionic states, mutual annihilation of vibrational fine structure occurs for all except the strongest vibrational states; the PES just reflects the resultants rather than full spectra.

Syntheses of Combretastatins D-1, D-2, and D-4 via Ring Contraction by Flash Vacuum Pyrolysis.

We report the syntheses of combretastatins D-2 and D-4 as well as a formal synthesis of combretastatin D-1 by a conceptually new route harnessing a ring-contracting flash vacuum pyrolytic extrusion of sulfur dioxide from the respective 16-membered sulfone precursors. Via flash vacuum pyrolysis, even metaparacyclophanes as small and strained as the hitherto unknown oxa[1.5]metaparacyclophane could be prepared as a side product en route to combretastatin D-2 by synchronous extrusion of SO and CO.

Synthesis, Structure, and Unusual Reactivity of a Stable 3-(Oxazolidin-2-ylidene)thiophen-2-one.

Treatment of 2- and 3-thienyloxazolines with butyllithium and bis(trimethylsilyl) peroxide results in ring hydroxylation to give products that exist mainly as the oxazolidinylidenethiophenones. The 3-oxazolidinylidenethiophen-2-one is a rare example of a stable heterocyclic o-quinone methide analogue that shows a varied pattern of reactivity, including both C- and O-alkylation, Michael addition via C-5 to an acetylenic ester, tetrachlorobenzannulation across positions 4 and 5, and formation of a hexacyclic fused-ring product with N-phenyltriazolinedione. Crystal structures of the products are dominated by inter- and intramolecular NH to CO hydrogen bonding.

Synthesis, structure and pyrolysis of stabilised phosphonium ylides containing saturated oxygen heterocycles.

A range of twelve stabilised phosphonium ylides containing tetrahydrofuran, tetrahydropyran or 2,2-dimethyl-1,3-dioxolane rings have been prepared and fully characterised, including one X-ray structure determination of each type. The X-ray structures confirm the P=C and C=O functions to be syn and all the compounds undergo thermal extrusion of Ph3PO to give the corresponding alkynes. In some cases there is also competing loss of Ph3P to give different carbene-derived products and evidence has been obtained for the generation of 2-phenyloxete in this way.