Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(−)-myrtenol nitrate

Here we report the chemoselective synthesis of several important, climate relevant isoprene nitrates using silver nitrate to mediate a ’halide for nitrate’ substitution. Employing readily available starting materials, reagents and Horner–Wadsworth–Emmons chemistry the synthesis of easily separable, synthetically versatile ‘key building blocks’ (E)- and (Z)-3-methyl-4-chlorobut-2-en-1-ol as well as (E)- and (Z)-1-((2-methyl-4-bromobut-2-enyloxy)methyl)-4-methoxybenzene has been achieved using cheap, ’off the shelf’ materials. Exploiting their reactivity we have studied their ability to undergo an ‘allylic halide for allylic nitrate’ substitution reaction which we demonstrate generates (E)- and (Z)-3-methyl-4-hydroxybut-2-enyl nitrate, and (E)- and (Z)-2-methyl-4-hydroxybut-2-enyl nitrates (‘isoprene nitrates’) in 66–80% overall yields. Using NOESY experiments the elucidation of the carbon–carbon double bond configuration within the purified isoprene nitrates has been established. Further exemplifying our ‘halide for nitrate’ substitution chemistry we outline the straightforward transformation of (1R,2S)-(−)-myrtenol bromide into the previously unknown monoterpene nitrate (1R,2S)-(−)-myrtenol nitrate

Measurement of isoprene nitrates by GCMS

According to atmospheric chemistry models, isoprene nitrates play an important role in determining the ozone production efficiency of isoprene; however this is very poorly constrained through observations as isoprene nitrates have not been widely measured. Measurements have been severely restricted largely due to a limited ability to measure individual isoprene nitrate isomers. An instrument based on gas chromatography/mass spectrometry (GCMS) and the associated calibration methods are described for the speciated measurements of individual isoprene nitrate isomers. Five of the primary isoprene nitrates which formed in the presence of NOx by reaction of isoprene with the hydroxyl radical (OH) in the Master Chemical Mechanism are identified using known isomers on two column phases and are fully separated on the Rtx-200 column. Three primary isoprene nitrates from the reaction of isoprene with the nitrate radical (NO3) are identified after synthesis from the already identified analogous hydroxy nitrate. A Tenax adsorbent-based trapping system allows the analysis of the majority of the known hydroxy and carbonyl primary isoprene nitrates, although not the (1,2)-IN isomer, under field-like levels of humidity and showed no impact from typical ambient concentrations of NOx and ozone

Upper-rim functionalised calix[4]arenes for chemoselective Au3+ detection

A unique, readily synthesised, upper-rim 1,3-difunctionalised calix[4]arene is reported; equipped with a fluorophore and an alkyne it mediates the efficient chemoselective detection of Au3+. Its ability to detect Au3+ is not perturbed by Au+ or excess competing and or contaminating metal e.g. platinum, cadmium, mercury, silver, sodium, magnesium or potassium cations

“Dial Up and Lock In”: Asymmetric organo-Brønsted acid catalysis incorporating stable isotopes

An operationally simple organo-Brønsted-acid-catalyzed asymmetric and regioselective “dial up and lock in” of one or more stable isotopes into organic compounds is unknown. Here, we describe a newly designed, chemically versatile protocol mediating single- or multiple-isotope incorporation into aziridines via a one-pot, three-component, two-step process. By exploiting easy-to-generate isotope-derived starting materials, it allows complete control of isotope positioning, affords >95 atom % isotope incorporation, and generates cis-aziridines with excellent optical activities and regioselectivities. Demonstrating a “low entry point,” and thus easy access to a broad range of researchers, it requires no specialist laboratory equipment and employs readily attainable reaction conditions. Demonstrating their utility, the aziridines are easily transformed into sought-after chiral non-racemic α-amino acids appended with one to three (or more) identical or different isotopes. The widespread use of these compounds ensures that our methodology will be of interest to biological, medicinal, pharmaceutical, agrochemical, biotechnology, materials, and process chemists alike

Stable isotope hyperpolarisation in metabolite study and disease diagnosis: Why do it? How is it done? What is it good for?

Part of "Abstracts of the 27th International Isotope Society (UK group) symposium: Synthesis and applications of labelled compounds 2018"

Hydrostannation of Acetylenic Acid Derivatives

The reaction of acetylenedicarboxylic acid and propiolic acid with tributyltin hydride efficiently yields vinylic tin compounds bis(tributylstannyl) 2-tributylstannylbutenedioates (E/Z,1:20) and tributylstannyl 3-tributylstannylacrylates (E/Z,1:1), respectively, with regiochemistry similar to that seen in the reaction of the corresponding esters

A brief synthesis of β-iodofurans

5-Endo-dig iodocyclisations of alk-3-yn-1,2-diols 4, followed by in situ dehydration, lead to good yields of β-iodofurans 5, which can subsequently be converted into a wide range of derivatives 6-13, using transition metal-catalysed coupling reactions or halogen-metal exchange

α-amino acid Tröger base derivatives, possible conformationally restricted scaffolds?

The first synthesis of innovative α-amino acid conjugates of Tröger base is reported; their potential application as conformationally restricted scaffolds is proposed and has been investigated using high level ab initio calculations. © The Royal Society of Chemistry

Stereochemical features of iodocyclisations of 3-alkene-1,2-diols to beta-hydroxytetrahydrofurans

5-endo-Iodocyclisations of stereoisomers of 3-alkene-1,2-diols 9, 12, 15 and 18 are stereoselective and provide an efficient route to beta-hydroxytetrahydrofurans. (C) 2000 Elsevier Science Ltd. All rights reserved