Chemodivergent [3+2] and [4+2] Annulations of Isoindigos with Morita–Baylis–Hillman (MBH) Carbonates

On the basis of catalyst control, we developed a chemodivergent annulation strategy between isoindigos and <i>o</i>-amino-aryl Morita-Baylis-Hillman (MBH) carbonates for the highly efficient and selective synthesis of two types of polycyclic alkaloid scaffolds. The choice of catalyst critically determines the reaction pathway: the use of a tertiary phosphine promotes a [3+2] annulation, affording the desired products in up to 90% yields over two steps. Conversely, when DABCO is used as the catalyst, a [4+2] annulation takes place, affording the corresponding products in excellent yields (up to 96%). Furthermore, moderate to excellent enantioselectivities were attained by employing chiral catalysts.