An Expedient Radical Approach for the Decarboxylative Synthesis of Stereodefined All-Carbon Tetrasubstituted Olefins

Identifier:  imarina:9369120

Handle: https://hdl.handle.net/20.500.11797/imarina9369120

Authors:  Zeng, Q; Nirwan, Y; Benet-Buchholz, J; Kleij, AW

Abstract:
We report a user-friendly approach for the decarboxylative formation of stereodefined and complex tri- and tetra-substituted olefins from vinyl cyclic carbonates and amines as radical precursors. The protocol relies on easy photo-initiated alpha-amino-radical formation followed by addition onto the double bond of the substrate resulting in a sequence involving carbonate ring-opening, double bond relay, CO2 extrusion and finally O-protonation. The developed protocol is efficient for both mismatched and matched polarity substrate combinations, and the scope of elaborate stereodefined olefins that can be forged including drug-functionalized derivatives is wide, diverse and further extendable to other types of heterocyclic and radical precursors. Mechanistic control reactions show that the decarboxylation step is a key driving force towards product formation, with the initial radical addition under steric control. A radical-based, photo-catalyzed decarboxylative formation of stereodefined tri- and tetrasubstituted olefins is reported using various alpha-amino radical precursors and heterocycles as substrates. This user-friendly protocol combines a wide structural scope, easy drug and postsynthetic manipulations, and variation in both reaction partners. The mechanistic studies reveal a key CO2 extrusion step to enable the overall transformation. image