Transition‐Metal‐Free Cross‐Coupling of Benzothiophenes and Styrenes in a Stereoselective Synthesis of Substituted (E,Z)‐1,3‐Dienes

Abstract

A transition metal‐free one‐pot stereoselective approach to substituted (E,Z)‐1,3‐dienes was developed by using an interrupted Pummerer reaction/ligand‐coupling strategy. Readily available benzothiophene S‐oxides, which can be conveniently prepared by oxidation of the parent benzothiophenes, undergo Pummerer coupling with styrenes. Reaction of the resultant sulfonium salts with alkyllithium/magnesium reagents generates underexploited hypervalent sulfurane intermediates that undergo selective ligand coupling, resulting in dismantling of the benzothiophene motif and the formation of decorated (E,Z)‐1,3‐dienes.

C‐Aryl Glycosylation via Interrupted Pummerer Rearrangement†

“…[ 4‐5 ] The representative route for C ‐aryl glycoside construction is nucleophilic substitution from arylmetal species toward glycosyl electrophiles, such as arylzincates, [ 6‐8 ] arylaluminates, [ 9‐11 ] and Grignard reagents. [ 12‐13 ] Pummerer rearrangement [ 14 ] is a powerful reaction, featured with sulfonium‐tethered [3,3]‐sigmatropic rearrangement, offering efficient construction of carbon‐ carbon bonds without transition metal catalysis, [ 15‐20 ] enabling functionalization at β position of sulfinyl group (Figure 1b). [ 21 ] Based on our research of glycal [ 22 ] and organosulfur chemistry, [ 23 ] C ‐aryl glycosides and 1,2‐dihydrobenzofuran‐fused C ‐aryl glycosides herein were constructed via interrupted Pummerer process between sulfoxide glycals and phenols (Figure 1c).…”