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[2+2] Photocycloaddition of 3‐Alkenyloxy‐2‐cycloalkenones: Enantioselective Lewis Acid Catalysis and Ring Expansion
Author(s) -
Brimioulle Richard,
Bach Thorsten
Publication year - 2014
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201407832
Subject(s) - enantioselective synthesis , chemistry , triethylsilane , ring (chemistry) , intramolecular force , cyclobutane , lewis acids and bases , racemization , catalysis , cleavage (geology) , medicinal chemistry , yield (engineering) , stereochemistry , organic chemistry , geotechnical engineering , fracture (geology) , engineering , materials science , metallurgy
Abstract By application of substoichiometric amounts (50 mol %) of a chiral Lewis acid, the intramolecular [2+2] photocycloaddition of the title compounds was achieved with high enantioselectivity (up to 94 % ee ). Upon cleavage of the cyclobutane ring the resulting tricyclic products underwent ring‐expansion reactions under acidic conditions and formed anellated seven‐ or eight‐membered‐ring systems without racemization. The ring expansion could be combined with a diastereoselective reduction (triethylsilane) or allylation (allyltrimethylsilane) upon BF 3 catalysis (48–87 % yield).