A Homo [3+2] Dipolar Cycloaddition: The Reaction of Nitrones with Cyclopropanes

Abstract

Pole-to-pole: Cyclopropanediesters when treated with nitrones in the presence of catalytic ytterbium triflate undergo a dipolar homo [3+2] cycloaddition to form tetrahydro-1,2-oxazines diastereoselectively (see scheme). This new process has been used in a two-step preparation of the tricyclic core of FR-900482.