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Lewis base and Brønsted base controlled chemodivergent annulations of α‐methyl substituted allenyl imide and o‐aminotrifluoroacetophenones are realized to afford highly valuable furo[3,2‐b]indol‐2‐ones and dihydroquinolines bearing a CF3‐substituted quaternary stereogenic center. The possible reaction mechanisms are proposed through deuterium labelling experiments. This work demonstrates the unprecedented dual reactivities of α‐methyl substituted allenyl imide with electrophilic−nucleophilic compounds in annulation reactions, and features chemodivergence in transforming allenyl imide through β'‐C−H functionalization via phosphine catalysis and β/γ‐bisfunctionalization via Brønsted base catalysis. [ABSTRACT FROM AUTHOR]

Unprecedented phosphine‐catalyzed [4+1] cycloadditions of allenyl imides have been discovered using various N‐based substrates including methyl ketimines, enamines, and a primary amine. These transformations provide a one‐pot access to cyclopentenoyl enamines and imines, or (chiral) γ‐lactams through two geminal C−C bond or two C−N bond formations, respectively. Several P‐based key intermediates including a 1,4‐(bis)electrophilic α,β‐unsaturated ketenyl phosphonium species have been detected by 31P NMR and HRMS analyses, which shed light on the postulated catalytic cycle. The synthetic utility of this new chemistry has been demonstrated through a gram‐scaling up of the catalytic reaction as well as regioselective hydrogenation and double condensation to form cyclopentanoyl enamines and fused pyrazole building blocks, respectively. [ABSTRACT FROM AUTHOR]