Peer-Reviewed Journal Details
Mandatory Fields
Chen, S;Ibrahim, AA;Peraino, NJ;Nalla, D;Mondal, M;Van Raaphorst, M;Kerrigan, NJ
2016
September
Journal of Organic Chemistry
Catalytic Asymmetric Synthesis of Ketene Heterodimer beta-Lactones: Scope and Limitations
Published
4 ()
Optional Fields
TERT-BUTYLCYANOKETENE CYCLOADDITION ENANTIOSELECTIVE TOTAL-SYNTHESIS MUKAIYAMA-ALDOL-LACTONIZATION FATTY-ACID SYNTHASE DISUBSTITUTED KETENES NATURAL-PRODUCT ALDEHYDES DIMERIZATION KETOKETENES MECHANISM
81
7824
7837
In this article we describe extensive studies of the catalytic asymmetric heterodimerization of ketenes to give ketene heterodimer beta-lactones. The optimal catalytic system was determined to be a cinchona alkaloid derivative (TMS-quinine or Me-quinidine). The desired ketene heterodimer beta-lactones were obtained in good to excellent yields (up to 90%), with excellent levels of enantioselectivity (>= 90% ee for 33 Z and E isomer examples), good to excellent (Z)-olefin isomer selectivity (>= 90:10 for 20 examples), and excellent regioselectivity (only one regioisomer formed). Full details of catalyst development studies, catalyst loading investigations, substrate scope exploration, protocol innovations (including double in situ ketene generation for 7 examples), and an application to a cinnabaramide A intermediate are described. The addition of lithium perchlorate (1-2 equiv) as an additive to the alkaloid catalyst system was found to favor formation of the E isomer of the ketene heterodimer. Ten examples were formed with moderate to excellent (E)-olefin isomer selectivity (74:25 to 97:3) and with excellent enantioselectivity (84-98% ee).
WASHINGTON
0022-3263
10.1021/acs.joc.6b01481
Grant Details