Visible-light-promoted synthesis of gem-dihaloenones

Abstract

Visible light-promoted strategies were developed for the synthesis of gem-dihaloenones using alkynes and polyhalomethanes as the starting materials. The methods produce a broad range of gem-dibromoenones and gem-dichloroenones without using...

Photocatalytic Multicomponent Annulation of Amide-Anchored 1,7-Diynes Enabled by Deconstruction of Bromotrichloromethane

“…Combined with these experimental outcomes and previous related works [ 17 , 18 , 19 , 20 ], we proposed a plausible mechanism about this photoredox-catalyzed multicomponent annulation of 1,7-diynes. As shown in Scheme 5 , the photocatalytic cycle was initiated by the activation of Ir(III) with blue light irradiation to form the excited state Ir(III)* species, which reacts with BrCCl 3 to yield trichloromethyl radical A and a bromine anion, together with Ir(IV) complex via a single electron transfer (SET).…”

“…When a 4 Å molecular sieve was employed as dehydrating agent and dry EtOH as solvent under standard conditions, the reaction process was completely inhibited (Scheme 4b). In addition, the reaction was carried out in the presence of H 2 18 O (98 atom% 18 O), and the products 2a and 2a-O 18 were identified by HR-MS in a 3:1 ratio (Scheme 4c). These two survey results indicated that the oxygen source of the ester and carbonyl group in target products come from water.…”

“…Several control experiments were performed to gain mechanistic insight action pathway. Firstly, the use of a radical inhibitor TEMPO (2,2,6,6-tetrameth idinyloxy) successfully suppressed the reaction process, and the result confir trichloromethyl radical may be involved in these transformations (Scheme 4a Å molecular sieve was employed as dehydrating agent and dry EtOH as sol standard conditions, the reaction process was completely inhibited (Scheme 4 tion, the reaction was carried out in the presence of H2 18 O (98 atom% 18 O), and th 2a and 2a-O 18 were identified by HR-MS in a 3:1 ratio (Scheme 4c). These two sults indicated that the oxygen source of the ester and carbonyl group in targ come from water.…”

“…Compared with halodifluoromethyl reagents [ 14 ], CBrCl 3 or CBr 4 is also widely pursued as a catalyst, reagent, and mediator for the preparation of polyhalogenated compounds in various organic transformations [ 15 , 16 ]. Among them, these tetrahalomethanes can undergo homolytic cleavage to deliver a bromine radical and a trihalomethyl radical by using visible light irradiation, which provides a green and efficient method for preparing important gem -dihaloalkene scaffolds through double cleavage of C-Br and C-X (X = Cl, Br) bonds ( Scheme 1 a, path I) [ 17 , 18 , 19 , 20 ]. In contrast to the well-developed methodology for building up gem -dihaloalkenes by means of tetrahalomethanes as radical precursor, investigations on bromotrichloromethane serving as C1 sources via quadruple cleavage are considerably less common ( Scheme 1 a, path II).…”

Visible photons as ideal reagents for the activation of coloured organic compounds

“…130 A similar approach was also proposed by using aqueous DMSO or neat alcohols as reaction media. 131 The generation of a trihalomethyl radical was also exploited in the iron(0) catalysed benzannulation of allylarenes to form 1-halonaphthalenes. 132 Umemoto's reagent 24.1 (Scheme 24) has traditionally been employed in photoredox catalysed trifluoromethylation.…”