Rh-Catalysed hydroacyloxylation of cyclopropenes: regio- and diastereoselective synthesis of acyloxycyclopropanes

Acyloxycyclopropanes are essential building blocks in biological and medicinal chemistry. However, their accessibility is severely limited by the need to pre-synthesise highly reactive cyclopropane derivatives. Herein, we report an efficient stereoselective synthesis of polysubstituted acyloxycyclopropanes via Cp*Rh(iii)-catalysed hydroacyloxylation of cyclopropenes. This catalytic system allows the regio-, facial-, and syn-selective addition of various inexpensive and commercially available carboxylic acids to the double bond of cyclopropene. This protocol is carried out under very mild conditions and shows a wide group tolerance, providing undescribed acyloxycyclopropanes with very good yields and exclusive diastereoselectivity. Furthermore, the reaction can be carried out intramolecularly towards interesting cyclopropyl spiro-lactones. Isolation of key organometallic complexes, NMR monitoring studies, HMRS experiments and DFT calculations have revealed significant mechanistic insights.