Asymmetric Catalysis of Chiral Bifunctional Selenides and Selenonium Salts Bearing a Urea Group

Abstract

Catalytic asymmetric reactions with chiral organoselenium catalysts have become one of the most important research topics in the field of organocatalysis. Despite the presence of several effective chiral selenium catalysts, further developments of new chiral organoseleniums are still desired due to their remarkable potential as asymmetric organocatalysts. Herein, we report the synthesis and asymmetric catalysis of chiral bifunctional selenides and selenonium salts bearing a urea group. The new chiral bifunctional selenide organocatalysts promote asymmetric halocyclizations with good to high levels of enantioselectivity. Furthermore, we report a reaction involving a precious example of a chiral tertiary selenonium salt‐catalyzed asymmetric phase‐transfer conjugate addition.

Selenonium Salt as a Catalyst for Nucleophilic Substitution Reactions in Water: Synthesis of Thiocyanites and Selenocyanates

“…Inspired by recent reports on the use of organochalcogenides, especially organochalcogenium salts, as chalcogen bond activators in organic transformations [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ], we decided to investigate whether selenonium salt C7 could catalyze the desired reaction. We compared its activity against C5 , which was the best catalyst tested previously.…”

“…Chalcogenonium salts (chalcogen IV species) are much better chalcogen bond donors compared with chalcogen (II) compounds, due to the depth of their σ-holes and increased Lewis acidity [ 5 , 6 , 7 ]. In recent years, research has focused on the application of selenonium salts as catalysts in various organic transformations [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].…”

Synthetic application of chalcogenonium salts: beyond sulfonium

“…Shirakawa et al reported the application of selenonium 73 as a phase-transfer catalyst to promote asymmetric conjugate addition of 3-phenyloxindole to N -phenyl-maleimide (Scheme 37). 62 Even though the adducts were obtained in good levels of diastereo- and enantioselectivity, the yields were low. Nevertheless, so far it has been the first report of application of a chiral selenonium salt to promote an asymmetric reaction.…”

Chiral sulfide and selenide catalysts for asymmetric halocyclizations and related reactions

“…A related chiral selenide catalyst ( S )- 6 bearing a urea moiety was also prepared (Scheme 16). 25 The utility of the chiral bifunctional selenide was demonstrated during asymmetric iodoaminocyclization. In the iodocyclization reactions, chiral bifunctional selenide catalysts provided enantioselectivities that were superior to those of chiral bifunctional sulfide catalysts.…”