Reactivity of cyclic sulfamidates towards phosphonate-stabilised enolates: synthesis and applications of α-phosphono lactams

Abstract

Five and six ring α-phosphono lactams 14–20 are available by reaction of 1,2- and 1,3-cyclic sulfamidates respectively with enolates derived from ethyl dialkylphosphonoacetates 3 and 4. Subsequent Wadsworth–Emmons olefination provides the enantiomerically pure exo-alkylidene variants e.g.25, which is efficiently converted to vinyl triflate 29 (>98% ee). Suzuki coupling of 29 to a range of aryl and vinyl boronic acids leads to a structurally diverse range of pyrrolidinones exemplified by 30 and 34. The degree of epimerisation at the base-sensitive C(5) stereocentre during the Suzuki coupling of 29 is shown to be dependent on both the nature of the aryl boronic acid and the reaction conditions used.