Facile scalable reduction of N-acylated dihydropyrazoles

The reduction of a variety of highly functionalized N-acylated dihydropyrazoles (1) with BH3 x pyridine is described. The process through which this unexpectedly difficult reduction was discovered and developed is reported. A facile atom-efficient route to the N-acylated dihydropyrazole reduction precursors (1) is also illustrated. The resulting acylpyrazolidine products (2) that arise upon reduction were isolated in good to high yields following exposure to reaction conditions which have been shown to tolerate a variety of different functional groups. Finally, this route has been demonstrated on a kilogram scale and provides direct access to potential proline surrogates for peptidomimetic applications.     

Pyrene‐Functionalised,Alternating Copolyimide for Sensing Nitroaromatic Compounds

A novel, pyrene‐functionalised copolymer has been synthesised in a single step via imidisation of poly(maleic anhydride‐alt‐1‐octadecene) with 1‐pyrenemethylamine, and its potential for the detection of volatile nitro aromatic compounds (NACs) evaluated. The new copolymer forms complexes in solution with NACs such as 2,5‐dinitrobenzonitrile, as shown by ¹H NMR, UV‐vis and fluorescence spectroscopy. Moreover, thin films of this copolymer, cast from THF solution, undergo almost instantaneous fluorescence quenching when exposed to the vapour of 2,5‐dinitrobenzonitrile (a model for TNT) at ambient temperatures and pressures.

     

A general route to 5-substituted-2-furylacetic acids: a brief synthesis of plakorsin B

3,4-Dihydroxy-5-alkynylcarboxylic acids, readily obtained by the addition of lithium acetylides to α-acetoxysuccinic anhydride followed by reduction and hydrolysis, undergo smooth silver(I)-catalysed 5-endo-dig cyclisations and in situ dehydration to give excellent overall yields of 5-substituted-2-furylacetic acids, including the natural metabolite plakorsin B.     

Pure Shear – A Footnote

A result on pure shear provides the motivation for the determination of some new general results relating real second order Cartesian tensors.      

Synthesis of the spirochroman core of dihypoestoxide and stereochemical proposal for the natural product

The tricyclic spirochroman core of dihypoestoxide has been synthesized from geranoic acid in seven steps using a hetero-Diels-Alder cycloaddition as a key step, thus providing support for the proposed biosynthesis of the natural product. Furthermore, analysis of the (13)C NMR data obtained for all four diastereoisomers of the synthetic spirochroman core has allowed us to propose a full stereochemical assignment for dihypoestoxide.     

Bounds on the diameter of Cayley graphs of the symmetric group

In this paper we are concerned with the conjecture that, for any set of generators S of the symmetric group \(\operatorname {Sym}(n)\) , the word length in terms of S of every permutation is bounded above by a polynomial of n. We prove this conjecture for sets of generators containing a permutation fixing at least 37 % of the points.