3-Chloro-2-(phenylsulfinyl)-1-propene and 3-Chloro-2-(phenylsulfonyl)-1-propene: Preparation and Utility as Reagents for α,α'-Annelation of Cyclic Ketones

Article abstract of DOI:10.1021/jo00191a017

The reaction of allyl chloride (7), at -40 deg C to -20 deg C, with in situ generated phenylsulfenyl chloride (6) affords exclusively the anti-Markovnikov product 1,3-dichloro-2-(phenylthio)propane (8) in 85-90percent yield.Oxidation of 8 with 1 equiv of MCPBA to sulfoxide 9 followed by DBU-catalyzed dehydrochlorination yields 3-chloro-2-(phenylsulfinyl)-1-propene (1d) (70percent).Treatment of 8 with 2 equiv of MCPBA yields sulfone 10 which is similarly dehydrochlorinated to 3-chloro-2-(phenylsulfonyl)-1-propene (1e)(81percent).The reaction of pyrrolidine enamines of cyclic ketones with 1d and 1.1 equiv of triethylamine in Me2SO at 95-100 deg C affords moderate yields of bicyclic keto thioenol ethers, formed via an α,α'-annelation-Pummerer reaction sequence, together with noncyclized, 2-(phenylsulfinyl)allylated ketone.Similar reactions with 1e provide good yields of bicyclic keto sulfones as approximate 1:1 mixtures of endo and exo isomers, which may be equilibrated to mixtures containing predominantly the exo compounds by treatment with methanolic sodium methoxide.