Stereospecific Synthesis of 2,3-Dimethyl-1,4-Thiamorpholines by Cyclization of β-N-Methoxycarbonylaminoalkyl Vinyl Sulfoxides and Related Compounds

Article abstract of DOI:10.1016/S0040-4020(01)85921-4

Synthesis of cis- and trans-N-methoxycarbonyl-2,3-dimethyl-1,4-thiamorpholine and their S-oxides and S,S-dioxides by intramolecular reaction of the corresponding 2-methoxycarbonylaminoalkyl-2'-chloroethyl thioethers, sulfoxides and sulfones with sodium hydride in dimethylformamide at room temperature is reported.Cyclization of chlorothioethers and -sulfones is stereospecific although, in the case of sulfones , the formed 1,4-thiamorpholines S,S-dioxides epimerize at C(2) after long reaction times.In chlorosulfoxides, elimination of HCl is previous to cyclization which also resulted stereospecific except in the case of the acyclic starting material of R*s,S*1,S*2 configuration, where epimerization at sulfur takes place.