One-Pot Alkynylation/Isomerization Cascade of β-Formylated Enoates to Functionalized Ynones.

The previously unknown γ-hydroxy esters bearing both propargylic and allylic alcohol moieties were obtained from β-formylated enoates and terminal alkynes. Their easy base-catalyzed allylic isomerization into γ-keto esters occurred chemoselectively under metal-free conditions. In contrast to the classical two-step synthesis of carbonyl compounds from allylic alcohols involving an oxidation-reduction sequence, this protocol provides functionalized ynones in a single step from readily available starting materials.

Reactions of α-Functionally Substituted Enals with Terminal Alkynes: Unexpected Assembly of 2-Amino-2-Cyclopentenones.

The reactions of α-chalcogen, α-halo, or α-amino functionally substituted enals with terminal alkynes leading either to corresponding propargyl alcohols (for O-, S-, Cl-, and Br-bearing substrates) or unexpected 2-amino-2-cyclopentenones (for aminoenals) are described. The key feature of these reactions is the rearrangement of adducts bearing amino groups on silica gel that triggered further cyclization to five-membered carbocycles.