An efficient [4 + 1] annulation reaction between in situ
generated
azoalkene intermediates and α-bromocarbonyls has been established.
A series of skeletally diverse aza-heterocycles with a functionalized
quaternary center were obtained in up to 89% yield under mild conditions.
The chemoselective annulation of aza-ortho-quinone
methide generated by in situ o-chloromethyl sulfonamide
has been achieved with bifunctional acyclic olefin. This efficient
approach provides access to the diastereoselective synthesis of functionalized
tetrahydroquinoline derivatives containing indole scaffolds through
the inverse-electron-demand aza-Diels–Alder reaction under
mild reaction conditions with excellent results (up to 93% yield,
> 20:1 dr). Moreover, this article realized the cyclization of
α-halogeno
hydrazone with electron-deficient alkene affording the tetrahydropyridazine
derivatives, which had never been reported.
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