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NHC-Catalyzed Enantioselective Dearomatizing Hydroacylation of Benzofurans and Benzothiophenes for the Synthesis of Spirocycles
Ist Teil von
ACS catalysis, 2016-09, Vol.6 (9), p.5735-5739
Ort / Verlag
American Chemical Society
Erscheinungsjahr
2016
Link zum Volltext
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Benzofurans and benzothiophenes have been efficiently employed as substrates in an enantioselective intramolecular hydroacylation. Breaking aromaticity in a 5-exo-trig cyclization of easily accessible heteroarenes by NHC-catalyzed hydroacylation gives access to a simple class of mainly unexplored spirocycles with up to 99% enantiomeric excess (ee). The formed product class bears interesting three-dimensional pseudoaxial chirality and shows typical ketone reactivity. Density functional theory (DFT) calculations reveal erosion of the ee via a stepwise mechanism bearing a hetero Wheland intermediate. Theoretical data are in agreement with deuterium-labeling studies and a linear correlation between electronics (σ) and the ee.