Treatment of α-alkylcinnamaldehydes with orthoesters, alcohols, or thiols in the presence of BF3·OEt2 induces an intramolecularelectrophilicaromaticsubstitution reaction to afford 1-alkoxy-2-alkylindenes. The reaction mechanisms of the indene formation have been elucidated on the basis of the reaction behaviors of β-deuterated α-methylcinnamaldehyde and the NMR studies of the reaction mixture. The
Asymmetric Nazarov Cyclizations of Unactivated Dienones by Hydrogen‐Bond‐Donor/Lewis Acid Co–Catalyzed, Enantioselective Proton‐Transfer
作者:Jan B. Metternich、Martin Reiterer、Eric N. Jacobsen
DOI:10.1002/adsc.202000831
日期:2020.10.6
cyclization catalyzed by chiral hydrogen‐bond‐donors in concert with silyl Lewis acids. The developed transformation provides access to tri‐substituted cyclopentenones in high levels of enantioselectivity (up to 95% e.e.) from a variety of simple unactivated dienones. Kinetic and mechanistic studies are consistent with a reversible 4π‐electrocyclization C−C bond‐forming step followed by rate‐ and enantio‐determining