Alkynyl Halo-Aza-Prins Annulative Couplings

Exploring Interrupted Nazarov Cyclizations Using Tethered Sulfonamide Nucleophiles: Insights into Capture Pathways

This manuscript describes a study of diverse reaction outcomes that stem from the ionization of aza-alkynyl-Prins adducts. Experimental results have demonstrated unexpected behavior in the nitrogen-containing systems compared to the analogous oxygen derivatives derived from oxa-Prins/halo-Nazarov sequences. In-depth experimental studies and computational analysis revealed an intricate mechanism involving competing halo-Nazarov and imino-Nazarov pathways. These findings further elucidate the reaction chemistry of 3-halo-pentadienyl cation intermediates, and expand their utility in synthetic transformations.

Stereoselective synthesis of gem-dihalopiperidines via the halo-aza-Prins cyclization reaction: access to piperidin-4-ones and pyridines

An efficient methodology for the synthesis of 4,4-dihalopiperidine derivatives in excellent yields has been developed using N-(3-halobut-3-en-1-yl)-4-methylbenzenesulfonamide and an aldehyde catalyzed by In(OTf)3. The reaction involves an initial formation of a six-membered carbocation via the aza-Prins cyclization reaction followed by a nucleophilic attack by a halide ion to give 4,4-dihalopiperidine. The dihalopiperidine is converted to tetrahydropiperidinone using Ac2O/Et3N in DCM/H2O (1 : 1). It is also utilized for the synthesis of pyridine scaffolds by treatment with DBU. Furthermore, the dihalopiperidine is transformed to its enol ether derivatives using KOH in alcohol.