Australian Journal of Chemistry Australian Journal of Chemistry Society
An international journal for chemical science
Australian Journal of Chemistry

Australian Journal of Chemistry

Volume 67 Numbers 8 & 9 2014

Dedication to Roger F. C. Brown

CH14103Dedication to Professor Roger F. C. Brown

Frank. W. Eastwood
pp. 1142-1145
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The foreword to this special issue dedicated to Professor Roger F. C. Brown provides a biographical introduction, an account of his scientific education in the 1950s, and a selection of research contributions from 1962. It highlights his work on flash vacuum pyrolysis, the study of reactive intermediates, and some natural product syntheses.

CH14102Indigo Dreaming

Ian D. Rae
pp. 1146-1149
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Ian Rae, Roger Brown’s first Ph.D. student, explored dithiole chemistry but failed to synthesise thiolutin. Now a historian of chemistry, he recounts the story of J. F. G. Fletcher, who returned to Australia in 1919 after munitions work in Britain, dreaming of the synthesis of indigo from naphthalene. He succeeded, but was unable to commercialise the process.

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Types of pyrolysis equipment, methods, and reactions are narrated including flash vacuum pyrolysis (FVP) for preparative or spectroscopic use, very low pressure pyrolysis, laser pyrolysis, pulsed pyrolysis, solvent spray pyrolysis, pipto-pyrolysis (‘falling solid pyrolysis’), vacuum gas–solid reactions, microwave and flash-flow pyrolysis..

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Methylenecycloheptadienyne 11 (heptafulvyne) is obtained very cleanly by flash vacuum thermolysis (FVT), but its facile thermal rearrangement to phenylacetylene 12 and benzocyclobutadiene 13 is ascribed to chemical activation, which is also invoked in the rearrangement of p-, m-, and o-phenylenebiscarbenes 2527 to phenylacetylene 12.

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In recent years, selective microwave heating of specific reagents has been reported several times in the literature for microwave-assisted synthesis of different nanoparticles. In the current study, the existence of selective microwave absorption in the synthesis of CdSe quantum dots using silicon carbide reactor technology as a control experiment was investigated and no evidence for this phenomenon was observed.

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The tricyclic core of eunicellin natural products was synthesised, employing an exo-selective Diels-Alder cycloaddition catalysed by the MacMillan imidazolidinone catalyst. This approach was further developed to address the issue of hydroxylation at the C8 position, and a novel scalable method for the extension of the medium-ring lactone to a cyclic ether was developed.

CH14098The Elusive Ethenediselone, Se=C=C=Se

Carl Th. Pedersen, Ming Wah Wong, Kazuo Takimiya, Pascal Gerbaux and Robert Flammang
pp. 1195-1200
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Ethenediselone, Se=C=C=Se, is characterised by neutralisation–reionisation mass spectrometry as a product of flash vacuum thermolysis (FVT) of tetraselenafulvalenes. Alkynes, CSe2, and selenoketene, H2C=C=Se were identified by matrix infrared (IR) spectroscopy. Se=C=C=Se is predicted to be a ground state triplet molecule with a very small singlet-triplet gap.

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The condensation of (chlorocarbonyl)ketenes 1 with N-phenylthiocarbamates 2 and N-phenylcarbamates 6 is postulated to lead to the formation of unstable mesoionic 1,3-thiazinium 4-olates I or 1,3-oxazinium 4-olates II, respectively.

CH14107Acanthocyclamine A From the Indonesian Marine Sponge Acanthostrongylophora ingens

Ariyanti S. Dewi, Tri A. Hadi, Nurrahmi D. Fajarningsih, Joanne T. Blanchfield, Paul V. Bernhardt and Mary J. Garson
pp. 1205-1210
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A new 3-alkylpiperidine compound (-) acanthocyclamine A (1) has been obtained from the methanolic extract of Acanthostrongylophora ingens (order Haplosclerida, family Petrosiidae). The structure of 1 was investigated by extensive 1D- and 2D-NMR experiments. The absolute configuration of 1 has been established by X-ray crystallography from anomalous dispersion effects using Cu radiation as C2 (R), C3 (R), C7 (R), and C9 (R). A plausible biosynthetic scheme leading to 1 is presented.

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Fused N,O-containing medium-sized ring systems provide significant opportunities as novel scaffolds for pharmaceutical development. Further synthetic methodologies are required to access these systems. Intramolecular nucleophilic displacement is one such methodology which now provides a concise entry to benzo[b]thieno-annulated [1,5]-oxazocinone, oxazoninone, and oxazecinone derivatives.

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Enantiopure precursors 2 were obtained using enzymatic resolution of 1 with R = 6-CO2Et. The 6-CO2Et was replaced with Br, which upon treatment with Me2CuLi followed by an appropriate electrophile gave a variety of precursors 2. Subsequent FVT gave enantiopure cyclopentenones 3 in high optical and chemical yields.

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The stereoselectivity of the nucleophilic addition of lithium dimethylcuprate and lithium di-n-pentylcuprate to 6-substituted tricyclo[,6]deca-4,8-dienones was investigated. Depending on the nature of the substituent at C-6, in some cases complete endo selectivity was observed, whilst in other cases the exo–endo ratio varied. The results were rationalised in terms of steric and/or electronic effects. Flash vacuum thermolysis of the products obtained gave β-substituted cyclopentenoids.

CH14121The Preparation of Macrocyclic Calpain Inhibitors by Ring Closing Metathesis and Cross Metathesis

Seth A. Jones, Joanna Duncan, Steven G. Aitken, James M. Coxon and Andrew D. Abell
pp. 1257-1263
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Two approaches to a new macrocyclic calpain inhibitor are reported. The inhibitor contains an N-terminal 4-fluoro-phenyl-sulfonyl group found in acyclic inhibitors and its backbone is constrained into a β-strand geometry known to favour active site binding. Compound 2 is a potent inhibitor of calpain II.

CH14135Synthesis, Structures, and Conformations of Linked Bis-Glyoxylamides Derived from Bis-Acylisatins

Venty Suryanti, Glenn C. Condie, Mohan Bhadbhade, Roger Bishop, David StC. Black and Naresh Kumar
pp. 1270-1278
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A series of bis-glyoxylamides possessing hydrophobic alkyl chains was successfully synthesised by ring opening of bis-acylisatins with amines or amino acid alkyl esters. The crystal structures revealed the interplay of intra- and intermolecular interactions (NH···O and C=O···C=O interactions) and the conformations of these long molecules.

CH14171Probing Mechanisms of Aryl–Aryl Bond Cleavages under Flash Vacuum Pyrolysis Conditions

Edward A. Jackson, Xiang Xue, Hee Yeon Cho and Lawrence T. Scott
pp. 1279-1287
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Flash vacuum pyrolysis (FVP) of phenyl-substituted polycyclic aromatic hydrocarbons (PAHs) promotes the formation of new rings by thermal cyclodehydrogenation reactions; however, such reactions are often accompanied by competitive loss of the phenyl group. Such ‘phenyl loss’ reactions cleave strong aryl–aryl bonds and are therefore important to understand. As probes for the mechanism(s) involved in the ‘phenyl loss’ reaction, FVP experiments were conducted with several phenyl-substituted PAHs and larger biaryls.

CH14155Unexpected Pyrolytic Behaviour of Substituted Benzo[c]thiopyran and Thieno[2,3-c]thiopyran S,S-dioxides

R. Alan Aitken, Clémence Hauduc, M. Selim Hossain, Emily McHale, Adrian L. Schwan, Alexandra M. Z. Slawin and Colin A. Stewart
pp. 1288-1295
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Flash vacuum pyrolysis of eight variously substituted ring-fused thiopyran S,S-dioxides results mainly in fragmentation via loss of SO from ring-expanded 7-membered ring sultines and subsequent rearrangement of the resulting diradicals to give a variety of novel products.

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The status quo for stabilization of cyclopentadiene-related bridged allylic anions has been assessed and new DFT calculations carried out to facilitate comparisons between different systems. This work supports the presence of homoaromaticity in the bicyclo[3.2.1]octadienyl anion and closely related species, augmented by inductive effects and ion-pairing.

CH14217Nonstabilised Azomethine Ylids from N-Oxides: Unravelling the Deprotonation of N-Methylmorpholine N-Oxide

Paul Malek Mirzayans, Elizabeth H. Krenske and Craig M. Williams
pp. 1309-1317
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NAY SAYers. Those wishing to utilise nonstabilised azomethine ylids have the right to complain about reaction condition choice. Higher temperature conditions predominate over lower temperature conditions, which limits the application of azomethine cycloadditions to robust dipolarophiles. We present a mechanistic analysis of the application of the Roussi reaction for low-temperature generation of nonstabilised azomethine ylids to the challenging substrate N-methylmorpholine N-oxide.

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The C-bonded cyanide structure Mn(CO)5(CN) is preferred energetically by ~60 kJ mol–1 over the N-bonded isocyanide structure Mn(CO)5(NC). Two end-to-end bridging µ-CN groups are found in all of the low-energy Mn2(CO)n(CN)2 structures (n = 8, 7).

CH14057Solvatochromism in Diketopyrrolopyrrole Derivatives: Experimental and Computational Studies

Rebecca S. Szabadai, Jesse Roth-Barton, Kenneth P. Ghiggino, Jonathan M. White and David J. D. Wilson
pp. 1330-1337
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Negative solvatochromism in substituted derivatives of diketopyrrolopyrrole arises from significant charge transfer existing in the ground states of these molecules that is reduced on excitation.

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Flash vacuum pyrolysis (FVP) has become an integral part of the synthesis of both flat and curved polycyclic aromatic hydrocarbons (PAHs). We report a new process to facilitate the cyclodehydrogenation of PAHs using an external radical source. This process has been shown to greatly increase the conversion of PAHs to their cyclodehydrogenated products.

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DFT with dispersion correction and expanded basis set computes N-chloro-N-dimethylaminoacetamide to be completely planar but with only 63 % the resonance energy of N,N-dimethylacetamide. N-chloro-N-methoxyacetamide has a much lower resonance (45 %) and it is pyramidal at nitrogen. These are unusual anomeric amides.

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Subjection of N-methyl carbazolone allyl carbonates bearing a propargyl side chain to Pd0 catalysis leads to the formation of enantioenriched γ-lactones, rather than the expected products of decarboxylative allylation. Following lactonisation, the Pd0 catalyst is regenerated by PdII reductive alkyne coupling.

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