Synthesis of 5,6-Dihydropyrazolo[5,1-a]isoquinolines through Indium(III)-Promoted Halocyclizations of N-Propargylic Sulfonylhydrazones

Alkynyl Halo-Aza-Prins Annulative Couplings

This article is a comprehensive report describing our studies in the field of aza-alkynyl Prins chemistry, comparing and contrasting the different reaction partners and reactivities observed during method development. The synthetic strategies combine an alkynyl aza-Prins coupling with an annulation, enabling the preparation of different nitrogen-containing heterocycles. Different iminium ions are explored as viable electrophiles for an alkynyl Prins cyclization, terminated by capture with a halogen nucleophile to form a vinyl halide. The synthetic utility of this functional handle is exploited through a number of Suzuki cross-couplings, allowing for the preparation of a modest library of compounds. In most cases, the Prins couplings are highly selective for the vinyl halides with E geometry, resulting from anti-addition across the alkyne.

Direct dilithiation of N-aryl heterocycles for the construction of condensed N-heterocycles

A 1,4-dilithio intermediate generated from N-aryl heterocycles reacts well with acyl chlorides to afford condensed N-heterocycles in good yields.

Synthesis of α-(aminoethyl)-α,β-enones via alkyne aza-Prins cyclization and their synthetic application to pyrrolidines

We developed a synthetic method for α-(aminoethyl)-α,β-enones from aryl-substituted homopropargyl sulfonamides and aldehydes, representing the first synthesis of conjugated enones via alkyne aza-Prins cyclization. These products could be converted into pyrrolidines by a formal 5-endo-trig cyclization.

Efficient synthesis of 2-aryl-2H-indazoles by base-catalyzed benzyl C-H deprotonation and cyclization

A straightforward and efficient method for the preparation of 2-aryl-2H-indazoles from ortho-alkyl substituted azoxybenzenes is presented. The reaction proceeds through base-catalyzed benzyl C-H deprotonation and cyclization to afford 2-aryl-2H-indazoles in good yields. This synthetic strategy can be applied to the construction of several fluorescent and bioactive molecules.

Copper-catalysed three-component carboiodination of arynes: expeditious synthesis ofo-alkynyl aryl iodides

A copper-catalysed three-component reaction of arynes, terminal alkynes, and NIS provides an expeditious approach too-alkynyl aryl iodides.

Pyrazole synthesis via a cascade Sonogashira coupling/cyclization of N-propargyl sulfonylhydrazones

An efficient approach for the preparation of pyrazoles via a Pd(ii)/Cu(i)-catalyzed Sonogashira coupling/cyclization of N-propargyl sulfonylhydrazones has been established.