Synthesis of Azaspiro Tricyclic Scaffolds through Post‐Ugi Modifications: Scope and Limitation of Aza‐Michael Cyclization

Abstract

Post-Ugi modifications offer a great tool to construct functionalized heterocycles in an atom-economic manner. Using this approach, we have constructed highly functionalized azaspiro tricyclic scaffolds that involve Ugi condensation and ipso-cyclization followed by aza-Michael ring closures. Herein, we present a detailed account of aza-Michael cyclizations with respect to substrate scope and limitations, along with new methods to prepare novel azaspiro tricyclic scaffolds.

Palladium(II)-Catalyzed Decarboxylative Difunctionalization of Alkynoic Acids To Access (E)-β-Sulfonylacrylamides and DFT Study

“…Although alkynes provide a wide compatibility in most of the transition-metal catalyzed transformations, the alkynoic acids serve as an excellent surrogate to offer extended scope in terms of reactivity and selectivity through decarboxylative functionalizations . There are elegant reports describing the use of alkynoic acids to obtain vinyl sulfones through decarboxylative sulfonylation in a regioselective manner. − However, the studies on the difunctionalization of alkynoic acids to prepare functionalized olefins are limited. − In our endeavors to develop efficient synthetic methods through alkyne functionalizations using isocyanides, − we achieved the synthesis of ( E )- and ( Z )-β-sulfonylacrylamides through a stereoselective difunctionalization of alkynes using sodium sulfinates and isocyanides in a stepwise manner (Scheme a) . The reaction proceeds via ( E )-β-iodovinylsulfone ( I ) that undergoes stereoselective amidation to yield ( Z )-β-sulfonylacrylamides ( II ) in one pot.…”