Cu‐promoted Access to 1,4‐Diazine‐Fused Isoindoles Through Concomitant C sp 3 −N and C sp 2 −N Bonds Formation Starting from Constrained N,O ‐acetals

Scarce dihydro‐1,4‐diazinoisoindole framework bearing two points of diversity was prepared through a cascade process based on concomitant C sp 3 − N and C sp 2 − N bond formation. This approach consists of an amidation in basic medium of a tosyl group by nucleophilic substitution followed by Cu‐mediated Goldberg reaction in the same operation. The required β‐bromoenamide bearing a tosyl group was obtained by tosylation of fused brominated N,O ‐acetals for the first time in acidic medium using submolar amounts of PTSA. The obtained piperazines are useful building blocks as illustrated by the formation of a pentacyclic product via the intramolecular interception of the enamide function.