Modular Synthesis of Triaroyl Cyclopropanes via a Formal Cyclotrimerization of Phenacyl Bromides and Their Transformation into Diazabicycles

Step-efficient cyclotrimerization reactions are entrancing approaches for saturated carbocycles. In this context, we demonstrate the α-bromocarbonyl (1+1+1) cyclotrimerization modularity to obtain stereoselective trisubstituted cyclopropanes under metal-free conditions. These cyclopropanes were condensed with hydrazine to afford diazabicyclic adducts and further expanded through a ring expansion reaction. In contrast to the classical alkylating reactivity, α-bromocarbonyl cyclotrimerization was also achieved by using various nucleophiles. A wide range of bromoacyl substrates established the broad scope of the transformation.