Cobalt-Catalyzed Annulation of Salicylaldehydes and Alkynes to Form Chromones and 4-Chromanones
A unique cobalt(I)–diphosphine catalytic system has been identified for the coupling of salicylaldehyde (SA) and an internal alkyne affording a dehydrogenative annulation product (chromone) or a reductive annulation product (4-chromanone) depending on the alkyne substituents. Distinct from related r...
Saved in:
| Main Authors: | , |
|---|---|
| Other Authors: | |
| Format: | Article |
| Language: | English |
| Published: |
2017
|
| Subjects: | |
| Online Access: | https://hdl.handle.net/10356/83163 http://hdl.handle.net/10220/42480 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Institution: | Nanyang Technological University |
| Language: | English |
| Summary: | A unique cobalt(I)–diphosphine catalytic system has been identified for the coupling of salicylaldehyde (SA) and an internal alkyne affording a dehydrogenative annulation product (chromone) or a reductive annulation product (4-chromanone) depending on the alkyne substituents. Distinct from related rhodium(I)- and rhodium(III)-catalyzed reactions of SA and alkynes, these annulation reactions feature aldehyde C−H oxidative addition of SA and subsequent hydrometalation of the C=O bond of another SA molecule as common key steps. The reductive annulation to 4-chromanones also involves the action of Zn as a stoichiometric reductant. In addition to these mechanistic features, the CoI catalysis described herein is complementary to the RhI- and RhIII-catalyzed reactions of SA and internal alkynes, particularly in the context of chromone synthesis. |
|---|