Synthesis of 2-Aryl Acetophenones via Hydrobromination and Oxy-isomerization of (o-Arylethynyl)benzyl Alcohols

Highly Reactive Hydrocarbon Soluble Alkylsodium Reagents for Benzylic Aroylation of Toluenes using Weinreb Amides

Deaggregating the alkyl sodium NaCH₂ SiMe₃ with polydentate nitrogen ligands enables the preparation and characterisation of new, hydrocarbon soluble chelated alkylsodium reagents. Equipped with significantly enhanced metalating power over their organolithium counterparts, these systems can promote controlled sodiation of weakly acidic benzylic C-H bonds from a series of toluene derivatives under mild stoichiometric conditions. This has been demonstrated through the benzylic aroylation of toluenes with Weinreb amides, that delivers a wide range of 2-arylacetophenones in good to excellent yields. Success in isolating and determining the structures of key organometallic intermediates has provided useful mechanistic insight into these new sodium-mediated transformations.

Addition of benzyl ethers to alkynes: a metal-free synthesis of 1H-isochromenes

Bromotrimethylsilane (TMSBr)-promoted intramolecular cyclization of (o-arylethynyl)benzyl ethers to form 1H-isochromenes at room temperature is reported. Further studies indicated that vinyl carbocations are the reaction intermediates which are stabilized by the conjugated aryl groups. Thus, O-addition of benzyl ethers/tetrahydropyrans to alkynes was achieved under metal-free, acidic conditions. These reaction conditions were compatible with an alkynyl Prins reaction; therefore, 1H-isochromenes were produced directly from alkynyl benzaldehydes and alkynyl alcohols using a one-pot procedure.