A Concise Synthesis of Fused Tricyclic Pyrrolo[3,2-d]pyrimidines

A concise approach to partially saturated fused tricyclic pyrrolo[3,2- d ]pyrimidines has been developed. Herein, we report a three-step route to the core templates, starting with a Sonogashira coupling and utilising either a CuI-catalysed or base-mediated 5- endo - dig cyclisation to form the pyrrolopyrimidine ring, followed by Mitsunobu cyclisation to afford the tricyclic system. This method facilitates synthetic access to a structural class with limited representation in the literature and is amenable to further elaboration by virtue of a halide incorporated at the 4-position.