A New Method of Generation of α-Selenocarbenium Ions from Se,O-Heteroacetals and Their Reactions

Article abstract of DOI:10.1021/jo00084a017

Various Se,O-heteroacetals were prepared by the LiAlH4 reduction of diselenides 1 followed by alkylation with methoxymethyl chloride or (2-methoxyethoxy)methyl (MEM) chloride.Olefinic and acetylenic α-seleno carbenium ions were generated by the selective C-O bond cleavage of O-(2-methoxyethyl)-Se,O-heteroacetals with titanium(IV) chloride and cyclized to give the seleno heterocyclic compounds.Olefinic MEM-selenides 3a,b,d-f,h underwent the endo-mode cyclization to afford 4-chloroselenacycloalkanes 4a,b,d-f,h in good yields, whereas acetylenic MEM-selenides 12b-e,g-j underwent the exo-mode cyclization to give 3-(1-chloroalkylidene)selenacycloalkanes 13b-e,g-j.This new utilization of α-seleno carbenium ions was also applied to the intramolecular and intermolecular Friedel-Crafts reactions.