A Cascade Reaction of Cinnamyl Azides with Acrylates Directly Generates Tetrahydro-Pyrrolo-Pyrazole Heterocycles

Developing reactions to generate
complex and modular building blocks
in a concise and direct fashion remains a contemporary synthetic challenge.
This work describes a stereoselective cascade reaction between allylic
azides and acrylates that directly generates tetrahydro-pyrrolo-pyrazole
ring systems. These products contain up to four contiguous stereocenters,
two of which may be tetrasubstituted carbon atoms attached to a nitrogen
atom. Over 30 examples are provided with an average isolated yield
of 71% (ranging from 40% to 94%). The reaction was easily scaled to
use more than one gram of starting material, and the products can
be readily diversified.