Copper‐Catalyzed (2+1) Annulation of Acetophenones with Maleimides: Direct Synthesis of Cyclopropanes

Abstract

A practical copper‐catalyzed direct oxidative cyclopropanation of electron‐deficient alkenes with acetophenone derivatives is reported. The dehydrogenative annulation involves a double CH bond functionalization at the α‐position of the ketone using di‐tert‐butyl peroxide as oxidant. The broad scope of the reaction and excellent functional‐group tolerance is demonstrated for the stereoselective synthesis of fused cyclopropanes. The developed transformation revealed an unprecedented reactivity for copper‐catalyzed processes.

Synthesis of 3‐Azabicyclo[3.1.0]hexane Derivates

“…Cyclic precursor maleimides as substrates were utilized in the construction of 3‐azabicyclic [3.1.0] hexane derivatives via cyclopropanation strategy. In 2015, Antonchick and co‐workers disclosed a direct copper‐catalyzed stereoselective cyclization of acetophenone derivative 6 and maleimide 7 for the synthesis of 3‐azabicyclic [3.1.0] hexane derivative 8 (Scheme 4a) [31] . Under an argon atmosphere, CuI was used as catalyst along with 2,2’‐bipyridine as ligand and di‐tert‐butylperoxide (DTBP) as the oxidant in chlorobenzene at 110 °C.…”