Metal-free halogen, chalcogen, or oxocarbenium ion mediated yne-carbonyl or yne-thioxo transformations of a range of N-and O-propargylic compounds have been studied. This investigation has led to the development of a mild, economic, and effective method for the synthesis of functionalized 4H-

Kabachnik-Fields reactions of various carbocyclic or heterocyclic acetylenic aldehydes together with subsequent Lewis acid catalyzed cyclizations have been studied. It was found that 5-exo-dig versus 6-endo-dig cyclization mode strongly depends on the structure of starting materials. Thus, nonaromatic acetylenic α-anilinomethylphosphonates underwent gold(III)-catalyzed or iodine-mediated 5-exo-dig cyclization to 1H-pyrrol-2-ylphosphonates. In contrast, electron-withdrawing heteroaromatic substrates formed 1,2-dihydropyridin-2-ylphosphonate ring containing materials via an exclusive 6-endo-dig ring-closure process. The dual mode of cyclization is possible only for α-amino (2-alkynylphenyl)methylphosphonates containing a benzene ring.

Catalyst-free addition of ketone enolate to nonactivated multiple CÀCb onds involves non-complementary reaction partners and typically requires super-basic conditions. On the other hand, highly aggregated or solvated enolates are not reactive enough to undergo direct addition to alkenes or alkynes.Herein, we report an ew anionic cascade reaction for one-step assembly of intriguing molecular scaffolds possessing contiguous six-, five-, and four-membered rings,r epresenting af ormal [2+ +2] enol-allene cycloaddition. Reaction proceeds under very mild conditions and with excellent diastereoselectivity.D eeper mechanistic and computational studies revealed unusually slow proton transfer phenomenon in cyclic ketone intermediate and explained peculiar stereochemical outcome.

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Tandem reactions of various acetylenic aldehydes with dimethyl phosphite in basic media were investigated. It was shown that in the case of a non-activated triple bond of the starting materials, the well-known Pudovik reaction followed by a subsequent phosphonate-phosphate rearrangement took place. On the other hand when the triple bond of the starting materials is activated by electron-withdrawing heterocycles, a smooth and regioselective tandem 5-exo-dig cyclization reactions becomes possible.