CuI-Catalyzed Asymmetric [3 + 2] Cycloaddition of Azomethine Ylides with Cyclobutenones.

The catalytic asymmetric 1,3-dipolar cycloaddition of cyclobutenones with azomethine ylides provides straightforward access to densely substituted 3-azabicyclo[3.2.0]heptanes. In the presence of CuI/(R)-Fesulphos as the catalytic system, high levels of diastereoselectivity and enantioselectivity were achieved (up to 98% enantiomeric excess (ee)).