An Integrated Building Block for Cascade Diels–Alder and Hetero-Diels–Alder Reactions

The Diels–Alder (DA) reaction and hetero-Diels–Alder (HDA) reaction are among the most powerful methods for the construction of carbocycles and heterocycles. Herein, an integrated building block of DA and HDA reactions is described. The triazenyl dienes could undergo a DA reaction, while the newly released alkene moiety and the triazene were able to engage in a HDA reaction. In these processes, the triazene group could facilitate the electron-demand DA reaction and also act as a fragment of diazadiene.