ZrCl4-promoted halogen migration during an electrophilic amination of halogenated phenols

An electrophilic amination of halogenated phenols with diisopropyl diazenedicarboxylate in the presence of ZrCl4 as a Lewis acid, accompanied by a halogen migration, was demonstrated for the first time; the fluorine, chlorine, bromine, or iodine atom migrated during the amination process under mild reaction conditions.     

A one-pot synthesis of functionalized 2,2-disubstituted 2H-1-benzopyrans

The synthesis of functionalized 2,2-disubstituted 2H-1-benzopyrans was achieved by condensing 2,3,5-trimethylhydroquinone (TMHQ) with ,β-unsaturated aldehydes or ,β-unsaturated acetals under acidic conditions.     

Acylation and related reactions under microwaves. 4. Sulfonylation reactions of aromatics.

Solvent-free sulfonylation of benzene and its activated or deactivated derivatives were carried out under microwave (MW) irradiation and a catalytic amount of iron(III) chloride, which, under these conditions, is more active than other metallic salts. With more reactive and/or nonvolatile reagents (anisole, xylenes, mesitylene) expeditious conditions (short reaction time at constant MW power without control of the temperature) were used. With less reactive and/or low-boiling reagents (benzene, toluene, halobenzenes), the rise in temperature and the increase of reaction time were controlled either by sequential MW irradiation or by a temperature order. It was shown that MWs cause preferential interactions with polar species present in the reaction, especially the aryl sulfone and its FeCl3-complexed form. A MW nonthermal effect was not observed when identical temperature gradients were produced by classical heating and MW irradiation, and if reaction temperature was strictly controlled.     

Thia-Fries rearrangement of aryl triflinates to trifluoromethanesulfinylphenols

Aryl triflinates are transformed to trifluoromethanesulfinylphenols in the presence of aluminum trichloride in dichloromethane at room temperature according to a thia-Fries rearrangement process. Rigorous exclusion of oxygen is necessary in order to avoid the formation of 2,2′-dihydroxybiaryls as secondary products.     

Synthesis of unsaturated [1,2]oxazines by using sigmatropic rearrangements and the ring-closing metathesis reaction

Various substituted unsaturated [1,2]oxazines have been synthesized by using a [2,3]- or a [3,3]-sigmatropic rearrangement and a ring-closing metathesis reaction as key steps.     

Chiral δ-Hydroxyalkyl Wittig Reagents: Synthesis and Reactivity

Abstract

enantioselective reduction of ketophosphonium salts give chiral synthons used in WITTIG reactions to prepare opticaly active ethylenic alcohols.     

Kinetic effects in radical addition reactions to radicophiles

Beyond expectation from polar effects rate acceleration is observed when captodative (cd) substituted 1,1-diphenylethylenes 6 and styrenes 7 undergo addition of isobutyronitrile radicals. The effect can be rationalised in terms of frontier orbital interactions.     

Enantioselective synthesis of both enantiomers of methyl dihydrojasmonate using solid-liquid asymmetric phase-transfer catalysis

Both enantiomers of methyl dihydrojasmonate (-)-1 and (+)-1 were obtained by a short route using asymmetric Michael addition of dimethyl malonate onto pentyl enone 3, followed by nonracemizing demethoxycarbonylation. The key enantioselective step involves a new system of asymmetric solid-liquid phase-transfer catalysis using solvent-free conditions. Enantiomeric excess as high as 90% (91% yield) was achieved.