Lewis acid mediated tandem reaction of propargylic alcohols to tetrazoles involving C-O- and C-C-bond cleavage reactions and a C-N-bond formation.

A novel and direct synthesis of 1-aryl-5-arylvinyl-tetrazoles from easily prepared propargylic alcohols and TMSN3 is developed in the presence of TMSCl under mild conditions (TMS = trimethylsilyl). The process involves an allenylazide intermediate, followed by a C-C-bond cleavage and C-N-bond formation to afford the desired products. Moreover, this method offers a good functional-group applicability and can be scaled-up to grams (yield up to 85 %).

TMSCl-mediated synthesis of α,ß-unsaturated amides via C-C bond cleavage and C-N bond formation of propargyl alcohols with trimethylsilyl azide.

A new method with high efficiency for the synthesis of α,ß-unsaturated amides from the easily prepared propargyl alcohols and TMSN3 using TMSCl as an acid promoter is developed. A wide variety of α,ß-unsaturated amides were produced in moderate to excellent yields. Mechanistic studies indicate that this transformation involves TMSCl-mediated allenylazide intermediate formation, C-C bond cleavage, and C-N bond formation. Significantly, this reaction shows good functional group compatibility and high regioselectivity, with a relatively short reaction time and inexpensive reagents.

Palladium-catalyzed/norbornene-mediated ortho-amination/N-tosylhydrazone insertion reaction: an approach to the synthesis of ortho-aminated vinylarenes.

ortho-Aminated vinylarene derivatives were obtained via a reaction of aryl iodides, N-benzoyloxyamines, and N-tosylhydrazones. This approach involves a palladium-catalyzed, norbornene-mediated ortho-amination/N-tosylhydrazone insertion reaction. In this transformation, one C-N bond and one C-C bond are formed and an amine group is introduced at the ortho position successfully.

Copper-catalyzed one-pot trifluoromethylation/aryl migration/carbonyl formation with homopropargylic alcohols.

A novel copper-catalyzed one-pot functionalization of homopropargylic alcohols that involves trifluoromethylation, aryl migration, and formation of a carbonyl moiety has been developed. This reaction constitutes the first direct conversion of homopropargylic alcohols into CF3-containing 3-butenal or 3-buten-1-one derivatives in a regioselective manner. Mechanistic studies indicate that the 1,4-aryl migration proceeds through a radical pathway.

Facile synthesis of halogenated spiroketals via a tandem iodocyclization.

A strategy for the synthesis of spiroketal compounds through a tandem iodocyclization of 1-(2-ethynylphenyl)-4-hydroxybut-2-yn-1-one derivatives is presented. This reaction could proceed under very mild conditions in a short time and avoid the use of expensive and toxic metal catalysts. Moreover, the resulting halides can be further exploited by subsequent palladium-catalyzed coupling reactions, which act as the important intermediates for building other valuable compounds.

Brønsted acid catalyzed and NIS-promoted cyclization of diynones: selective synthesis of 4-pyrone, 4-pyridone, and 3-pyrrolone derivatives.

Brønsted acid catalyzed tandem cyclization was found to be highly effective for the preparation of a series of polysubstituted 4-pyrones from diynones (yield up to 99%). 4-Pyridone and 3-pyrrolone derivatives were also selectively synthesized by employing NIS and/or Brønsted acid. NIS as an electrophilic reagent could promote these reactions efficiently and rapidly under very mild reaction conditions.