Gavin L. Edwards

Cyclic enol ether synthesis via arenesulfonyl iodide additions to alkynols

Abstract The reaction of arenesulfonyl iodides with alkynols generally provides adducts in good yields. Treatment of these adducts with KN(SiMe3)2 gives enol ethers; cyclisation of the functionalised pentenol (5) results in formation of the exo-alkylidene tetrahydrofuran (7), whereas the homologous hexenol (6) gives the dihydropyran (8). Attempts to cyclise the hexenol (6) with potassium t-butoxide under the conditions reported by Short and Ziegler generally gave the endocyclic ether (8).

Alkylation of vinyl sulfones as a route to 2-alkylidene tetrahydrofurans

Abstract Deprotonation of the vinyl sulfone (2) with n-butyllithium and treatment of the resulting organolithium intermediate with an alkyl halide in the presence of hexamethylphosphoramide (HMPA) gives monoalkylated adducts in 14 to 61% yields. In general, excellent regioselectivity for alkylation α to the sulfone is observed.

Radical cyclisation from alkenyl oxaziridines

Abstract Some 6-oxa-1-azabicyclo[3.1.0]hexanes have been prepared by photoisomerisation of alkenyl nitrone esters and peracid oxidation of pyrrolines Their ring-opening reactions with iron(II) sulfate, tri-n-butyl tin hydride and copper(I)triphenylphosphine chloride in many cases afford the related pyrrolines, but some trans oxaziridines give products derived from the trapping of aminyl radicals by the pendant alkenes.

A non-enzymatic, asymmetric synthesis of dicyclopentadienone

Abstract A simple synthetic method for the preparation of optically active “;dicyclopentadionone”; is presented. The procedure involves the reaction of the magnesium enolate of the racemic ketone ( 2 ) with S S -menthyl- p -toluenesulfinate, giving a β-ketosulfoxide as a single diastereoisomer. Conversions to enome ( 1 ) or saturated ketone ( 2 ) proceed with good optical and chemical yields.

Intramolecular cycloaddition of 5-alkenyl-1-pyrroline 1-oxide-5-carboxylic esters

Abstract Some 5-alkenyl-1-pyrroline-1-oxide-5-carboxylic esters have been prepared by alkylation of a related nitrone carboxylic ester. On thermal treatment, they undergo regioselective intramolecular 1,3-dipolar cycloaddition to give a range of cycloadducts, which can be hydrogenolysed to generate azabicyclic compounds and unusual cyclic amino esters.

para-toluenesulfonyl iodide as a convenient, mild reagent for the preparation of functionalised cyclic ethers

Abstract Free radical addition of para-toluenesulfonyl iodide to alkenols occurs readily to give functionalised β-iodosulfones as single regioisomers. Cyclisation to give cyclic ethers is effected by treatment with potassium carbonate in methanol. An anomalous reaction, where a substituted alkenol cyclises directly to give an iodotetrahydropyran, is also discussed.

Bismuth(III) acetate: a cheap, efficient, and environmentally acceptable reagent for ‘wet’ and ‘dry’ prevost reactions

cis- and trans-Diol derivatives can be prepared from alkenes by reaction with bismuth(III) acetate in ‘wet’ and ‘dry’ acetic acid respectively.

The cyclosulfonylation reaction: A comment on the radical reactions of 4-pentenyl tosylate

Attempted free radical rearrangement of the para-toluenesulfonyl ester of 4-penten-1-ol in carbon tetrachloride gives only the simple Kharasch 1,2-adduct, instead of the 2-substituted tetrahydrofuran as claimed by Serra and da Silva Correa.

A new synthesis of spiroketals via sulfonyl-substituted dihydropyrans

Abstract 6,6- and 6,5-Spiroketals were prepared in good overall yields by alkylation and epoxide-opening reactions of 3,4-dihydro-6-[(para-toluenesulfonyl)methyl]-2H-pyran (1) and subsequent acid catalysed cyclisation. The diastereoselectivity of the cyclisations was determined by a combination of 2D-NMR spectroscopy and X-ray crystallography. Attempted preparation of a 7,6-spiroketal using the same methodology was unsuccessful.

Oxygen to carbon rearrangements of anomerically linked alkenols from tetrahydropyran derivatives: an investigation of the reaction mechanism via a double isotopic labelling crossover study

A variety of alkenol tetrahydropyran derivatives were prepared and subjected to a tin tetrachloride promoted anomeric oxygen to carbon rearrangement. Using this methodology many of the corresponding carbon-linked structures were synthesised, including alkenes and bicyclic ethers, in good yields. On the basis of an isotopic labelling study using 2H incorporated into the side chain and ring system it is proposed that these reactions proceed via an intermolecular pathway.