A. J. Bloodworth

A mild, convenient, halogen-exchange route to gem-difluorides and trifluorides.

Abstract Reaction of gem -dihalides R 1 R 2 CX 2 (X= Cl or I) and of PhCCl 3 with AgBF 4 at room or sub-ambient temperatures affords the corresponding gem -difluorides and trifluoride in unoptimised yields of 35–84%.

6-hydroxymethyl-1,2,4-trioxanes and derivatives: An alternative 1,2,4-trioxane synthesis from β′γ′-unsaturated β-hydroxyhydroperoxides

Abstract Allylic hydroperoxides CH 2 :C(Ph)CH(OOH)CH 2 OX (X  H, CONHPh, Ac), from regiospecific photooxygenation of allylic alcohols CH 3 C(Ph):CHCH 2 OX, form hemiperoxyacetals with aldehydes or ketones which upon cyclisation with mercury(II) trifluoroacetate then reduction with sodium borohydride diastereoselectively afford 1,2,4-trioxanes with XOCH 2 substituents at C-6.

One-bond C–H NMR coupling constants in 1,2,4-trioxanes: a reversed perlin effect

In a reversal of the Perlin effect, the values of 1JC–H for the equatorial protons at C(3) and C(6) in 1,2,4-trioxanes are less than those for the corresponding axial protons; this is ascribed to homoanomeric interactions between equatorially directed nonbonding electron pairs on oxygen and the equatorial C(3)–H or C(6)–H σ* orbitals.

Iron(II)-mediated rearrangement of 1,2,4-trioxanes into 1,2-diol monoesters via 1,5-hydrogen transfer

Abstract Five 3-alkyl- or 3-aryl-5,5,6,6-tetramethyl-1,2,4-trioxanes 4 upon treatment with iron(II) sulfate in aqueous acetonitrile under nitrogen for 12–72H are cleanly isomerised into the corresponding 2,3-dimethylbutan-2,3-diol monoesters 5 ; it is suggested that the reactions involve reduction to oxyl radicals followed by 1,5-hydrogen transfer, a sequence that has recently been implicated in the molecular mechanism of action of the antimalarial artemisinin.

Oxymetallation. Part 24. Preparation of cyclic peroxides by cycloperoxymercuriation of unsaturated hydroperoxides.

Abstract Seventeen unsaturated hydroperoxides have been converted by treatment with mercury(II) acetate and/or mercury(II) nitrate into nineteen new mercuriated cyclic peroxides and by subsequent demercuriation with alkaline sodium borohydride, six new mercury-free peroxides have been isolated. The results greatly extend the range of such reactions and provide information about the stereoselectivities and relative ease of several different modes of cycloperoxymercuriation. It is suggested that the reactions with mercury(II) acetate are kinetically controlled whereas those with mercury(II) nitrate show a component of thermodynamic control of product distribution.

A SHORT SYNTHESIS OF NATURALLY OCCURRING AND OTHER ANALOGUES OF PLAKINIC ACIDS THAT CONTAIN THE 1,2-DIOXOLANE GROUP

Abstract Natural and unnatural analogues 4 of plakinic acids A, C and D have been prepared in three steps from alkan-2-ones by (i) LDA-induced condensation with ethyl 3-methylbut-2-enoate to give (2Z)-3,5-dimethylalka-2,4-dienoic acids 10, then (ii) isomerisation to the 2E-isomers 5 and finally (iii) peroxymercuriation with 30% hydrogen peroxide and reduction in situ with sodium borohydride.

An NMR and ab initio MO study of the effect of β-oxygen in 1,3-dioxanes

NMR Measurements and ab initio calculations suggest that in 1,3-dioxanes the β-oxygen atoms have the effect of weakening the equatorial CH bond at the 5-position.

Versatility of the cyclo-oxymercuriation route to 1,2,4-trioxanes

Abstract The versatility of the cyclo-oxymercuriation route to 1,2,4-trioxanes is illustrated by preparing new examples with heterocyclic, unsaturated and carbohydrate substituents and by post-cyclisation modification of the substituents including oxidative cleavage of alkene and reduction, condensation and Wittig olefination of carbonyl groups.

Mercury(II)-mediated cyclisation of hydroperoxyalkylcyclopropanes: a new route to cyclic peroxides

Abstract Aldehydes, RCHO (R = Me, Et, i Pr, and c-C 6 H 11 ), have been converted via alkylation, cyclopropanation, oxidation, condensation with p -tosylhydrazine, reduction and perhydrolysis into 2-hydroperoxyalkylcyclopropanes, RCH(OOH)CH 2 c-C 3 H 5 , and thence by cycloperoxymercuriation and reductive demercuriation into the corresponding 3-alkyl-5-ethyl-1,2-dioxolanes.

Rate constants for the formation of oxiranes by γ-scission in secondary β-t-butylperoxyalkyl radicals

Rate constants for the title reactions have been determined from the ratios of oxirane to peroxide obtained in the reductions of β-bromoalkyl t-butyl peroxides with tributyltin hydride. At ca. 298 K the rate constants are 0.32, 1.12, 1.96, 2.0, and 6.2 × 106 s–1 for β-t-butylperoxy derivatives of trinorbornan-2-yl (exo) cyclohexyl, 1-methylpropyl, cyclopentyl, and 1-ethylbutyl, respectively. The results are discussed in terms of steric and electronic effects in the transition state leading to ring closure of the radicals.