New and Concise Syntheses of the Bicyclic Oxamazin Core Using an Intramolecular Nitroso Diels–Alder Reaction and Ring-Closing Olefin Metathesis.

Herein two new and concise synthetic approaches for making an unsaturated bicyclic oxamazin core are reported. The first involves the use of an intramolecular Diels–Alder reaction to form both of the fused rings in one step. The second approach incorporates ring-closing olefin metathesis in the final step to form the second fused ring of the core. The scope of the second approach was also expanded further to afford larger ringed bicyclic systems. [ABSTRACT FROM AUTHOR]