Visible-Light Photoredox Catalysis: Dehalogenation of Vicinal Dibromo-, α-Halo-, and α,α-Dibromocarbonyl Compounds

Abstract

vic-Dibromo-, α-halo-, or α,α-dibromocarbonyl compounds can be efficiently dehalogenated using catalytic tris(2,2'-bipyridyl)ruthenium dichloride (Ru(bpy)(3)Cl(2)) in combination with 1,5-dimethoxynaphthalene (DMN) and ascorbate as sacrificial electron donor. For this process, a visible light promoted photocatalytic cycle is proposed that involves the reduction of carbon halogen bonds via free radical intermediates.

Hantzsch Ester as a Photosensitizer for the Visible‐Light‐Induced Debromination of Vicinal Dibromo Compounds

“…[5] Both of these methods require a costly transitionmetal catalyst. In 2014, the photoreductive debromination using sexithiophene as photocatalyst was demonstrated by Scaiano and co-workers, who focused on stilbene and a-carbonyl dibromo compounds.…”

Synthesis and antiproliferative activity of α-branched α,β-unsaturated ketones

“…Low overall yields can be explained by possible side self-condensation reaction between two aliphatic aldehydes molecules. However, the mixtures of E (2) and Z (3) isomers of the corresponding a,bunsaturated ketones were formed during reaction of 1def with aromatic aldehydes, especially those having an ortho-substituent (Table 1, entries 14, 15, 17e19, 22,23,26). The reaction of 1d with 4-methoxybenzaldehyde was complicated and took longer times for the full conversion of the alkyne; and also a lot of tars were produced.…”

Iron‐Catalyzed Stereoselective Cross‐Coupling Reactions of Stereodefined Enol Carbamates with Grignard Reagents

“…[18] Theh ighest stereoselectivity for the synthesis of 26 that we could find was achieved by ar eductive debromination of the corresponding vicinal dibromide with an E/Z ratio of 5.25:1 with an overall yield of 65 %. [19] As can be seen in Table 2, the Fe-catalyzed cross-coupling between (E)-1 and phenethylmagnesium chloride gave 26 in an E/Z ratio of > 50:1 and 82 %yield. Finally, this method is readily scalable,with a20mmol scale reaction yielding almost identical yields and stereoselectivities as the same reaction on 1mmol scale (see compound 18 in Table 2).…”