Tandem Double-Cross-Coupling/Hydrothiolation Reaction of 2-Sulfenyl Benzimidazoles with Boronic Acids

Abstract

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Recent Metal-Catalyzed Methods for Thioether Synthesis

“…187 Alkyne hydrothiolation was also incorporated into a tandem reaction sequence for the synthesis of functionalized benzimidazoles 95 (Scheme 54). 188 Thioethers 93 were treated with 2 equivalents of boronic acids 94 in the presence of a Pd(0)…”

Recent developments in palladium-catalyzed C–S bond formation

“…Recently, Gulea and co-workers have demonstrated a unique palladium-catalyzed cascade Suzuki-Miyaura coupling/ desulfenylative coupling/hydrothiolation of 2-sulfenyl benzimidazoles (59) with boronic acids (60) for the preparation of various substituted benzimidazoles bearing a stereodefined alkenyl sulfide (61) (Scheme 24). 48 This cascade protocol was carried out with excess boronic acids (3 equiv. ), Pd 2 (dba) 3 (5 mol%), PCy 3 (20 mol%), and K 2 CO 3 (3 equiv.)…”

Synthesis of Medium-Sized Heterocycles by Transition-Metal-Catalyzed Intramolecular Cyclization

“…This represents a rare example of competing processes between 10-exo and 11-endo cyclocarbopalladation of alkynes. We also attempted to trap the vinyl-palladium intermediate by a Suzuki-Miyaura coupling instead of the reduction to produce benzimidazole-fused thiazocines bearing a stereo-defined tetrasubstituted exocyclic double bond; however, the yield was very low [43].…”

“…The cyclocarbopalladation is followed by an allene insertion and final capture of the resulting π-allyl palladium(II) species by a secondary amine nucleophile. The authors explored the possibility of forming an eight-membered ring using this methodology; therefore, one example was achieved starting from substrate 16, affording the desired tetrahydro-2benzoxocine 17 and the acyclic product 18 resulting from the direct coupling in a 1:1.4 mixture, with We also attempted to trap the vinyl-palladium intermediate by a Suzuki-Miyaura coupling instead of the reduction to produce benzimidazole-fused thiazocines bearing a stereo-defined tetrasubstituted exocyclic double bond; however, the yield was very low [43].…”