Chiral Brønsted acid-catalyzed asymmetric intermolecular [4 + 2] annulation of ynamides with para-quinone methides
Catalytic asymmetric transformations of ynamides have attracted considerable attention in recent years. However, most of them were limited to intramolecular reactions or required metal catalysts. Herein, a chiral Brønsted acid-catalyzed asymmetric intermolecular [4 + 2] annulation of ynamides with p...
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Veröffentlicht in: | Science China. Chemistry 2023-05, Vol.66 (5), p.1467-1473 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Catalytic asymmetric transformations of ynamides have attracted considerable attention in recent years. However, most of them were limited to intramolecular reactions or required metal catalysts. Herein, a chiral Brønsted acid-catalyzed asymmetric intermolecular [4 + 2] annulation of ynamides with para-quinone methides (
p
-QMs) is disclosed, which not only represents the first metal-free protocol for catalytic asymmetric nucleophilic addition of ynamides to electrophiles, but also constitutes the first enantioselective annulation between
p
-QMs and alkynes. This methodology leads to the practical synthesis of biologically important chiral 4-aryl-3,4-dihydrocoumarins and 4-aryl-coumarins. Preliminary control experiments indicate that the
ortho
-hydroxyphenyl substituted
p
-QMs could isomerize into
ortho
-quinone methides (
o
-QMs) in the presence of chiral catalyst, which further react with ynamides
via
enantioselective [4 + 2] annulation, to generate the chiral product. |
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ISSN: | 1674-7291 1869-1870 |
DOI: | 10.1007/s11426-022-1536-9 |