Abstract
A straightforward methodology for the regioselective synthesis of pyrazoles has been developed by a domino sequence based on a photoclick cycloaddition followed by a photocatalyzed oxidative deformylation reaction. Distinguishing features of this protocol include an unprecedented photoredox-catalyzed Norrish type fragmentation under green-light irradiation and the use of α,β-unsaturated aldehydes as synthetic equivalents of alkynes, where the aldehyde is acting as a novel photoremovable directing group.
Highlights
Pyrazoles are privileged structures in organic and medicinal chemistry, because they are present in numerous natural products and therapeutic agents based on small molecules, such as Celecobix, Rimonabant, or Lersivirine, among others.[1]
Synthesis of Pyrazoles and Pyrazolines from Tetrazoles α,β-Unsaturated aldehydes have been extensively used as dipolarophiles in 1,3-dipolar cycloadditions[13] with a great variety of dipoles.[14,15]
The synthetic versatility of the formyl group is beyond any doubt because it can be straightforwardly converted into many other functional groups
Summary
Pyrazoles are privileged structures in organic and medicinal chemistry, because they are present in numerous natural products and therapeutic agents based on small molecules, such as Celecobix, Rimonabant, or Lersivirine, among others.[1]. Synthesis of Pyrazoles and Pyrazolines from Tetrazoles α,β-Unsaturated aldehydes have been extensively used as dipolarophiles in 1,3-dipolar cycloadditions[13] with a great variety of dipoles.[14,15] The synthetic versatility of the formyl group is beyond any doubt because it can be straightforwardly converted into many other functional groups.
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