Visible-light-mediated Barbier allylation of aldehydes and ketonesviadual titanium and photoredox catalysis

Abstract

We report a photocatalytic Barbier-type allylation of various aldehydes and ketones with allyl bromide for the synthesis of homoallylic alcohols enabled by dual titanium and photoredox catalysis. This environmentally benign...

Activation of Chromium Catalysts by Photoexcited Hantzsch Ester for Decarboxylative Allylation of Aldehydes with Butadiene

“…Butadiene is one of the most convenient industrial raw materials and frequently used for organic synthesis. , Recently, transition metal-catalyzed three-component allylation of carbonyls with butadiene has attracted a great deal of attention due to its overall synthetic efficiency and environmental sustainability. − In particular, a radical-based Cr-catalyzed three-component allylation was first reported by Takai and further developed by Zhang and Glorius using fluoroalkyl iodides or 4-alkyl-HEs as radical precursors. − Carboxylic acids are highly attractive feedstocks in organic synthesis due to their excellent features, such as their low cost, abundance, easy operation, and large structural diversity. Photocatalytic radical decarboxylative functionalization through redox-active esters [ N -hydroxyphthalimide (NHPI) esters] by forming an electron donor–acceptor complex has achieved great success. − Specifically, in this work, the multiple roles of HE are to reduce redox-active esters to deliver alkyl radicals, to activate Cr catalysts, and to break the Cr–alkoxy bond, thereby bypassing exogenous photocatalysts, metallic reductants, and additives.…”

Organic thermally activated delayed fluorescence (TADF) compounds used in photocatalysis

“…110a), 277 the Barbier allylation of aldehydes and ketones (Fig. 110b) 278 and the allylation of carbonyls with 1,3-butadiene (Fig. 110c) 279 all of which use Cp 2 TiCl 2 as the titanium catalyst of choice.…”

“…For the Barbier allylation reaction, allyl bromide could also quench the PC, although at a slower rate than Cp 2 TiCl 2 (k q = 3.3 Â 10 9 L mol À1 s À1 and 5.8 Â 10 8 L mol À1 s À1 for Cp 2 TiCl 2 and allyl bromide, respectively, with 4CzIPN). 278 Again, in the allylation with 1,3-butadiene, BrCF 2 CO 2 Et could also act as a quencher but at a much slower rate (k q = 3.65 Â 10 9 L mol À1 s À1 and 3.05 Â 10 7 L mol À1 s À1 for Cp 2 TiCl 2 and BrCF 2 CO 2 Et, respectively, with [Ir(dF(CF 3 )ppy) 2 (dtbbpy)]PF 6 .…”

Sustainable radical approaches for cross electrophile coupling to synthesize trifluoromethyl- and allyl-substituted tert-alcohols

“…Barbier-type allylation has been the traditional approach to the synthesis of trifluoromethyl-and allylsubstituted tert-alcohols (Guo et al, 2017;Nie et al, 2011;Tordeux et al, 1990). The Barbier process involves the introduction of metal complexes, such as indium (Araki et al, 1988;Loh et al, 1999;Roy and Roy, 2010;Shen et al, 2013), zinc (Grellepois et al, 2017;Metzger et al, 2010;Yin et al, 2020), ruthenium (Cicco et al, 2017;Wang et al, 2017Wang et al, , 2021, titanium (Li et al, 2020), or mercury (Cao et al, 2016;Gong et al, 2019), into the carbon-halide/carbon-silyl bond for generating the reactive nucleophilic allylmetal intermediates, which react with the trifluoromethyl ketone to furnish the trifluoromethyl-and allyl-substituted tert-alcohol (Figure 1a). Despite these advantages, the Barbier reaction requires stoichiometric amounts of metals, and catalytic approaches are limited to the use of allylboron/allylsilane reagents that are difficult to prepare.…”