Catalytic Electrophilic Thiocarbocyclization of Allenes

Abstract

An efficient approach via catalytic electrophilic thiocarbocyclization of allenes to construct indene-based sulfides with excellent regioselectivities is disclosed. The reactions were carried out at low temperatures by selenide catalysis in the presence of TMSOTf. Not only electrophilic arylthio reagents but also electrophilic alkylthio reagents worked well under these conditions. Furthermore, the method could be applied to intermolecular azidothiolation of allenes.

NIS/HFIP‐Mediated Synthesis of Indene‐Based β‐Iodoalkenyl Sulfides from Propargylic Sulfides

“…Recently, alternative methods for synthesizing alkenyl sulfides based on transition metal‐free reactions under mild conditions have arisen as effective strategies [11] . In this regard, related 2‐indenyl sulfides were obtained upon the reaction of allenes with electrophilic sulfur sources like thiosuccinimides in the presence of diphenyl selenide as a catalyst [12] …”

“…[28] As a result, an allenyl thioether C is generated. This species could react with electrophiles [12,15] similarly to related carbon-substi-tuted allenes generating the iodonium D. Further evolution of D generates a pentadienyl-type carbocation E stabilized by the S-atom. Finally, a Nazarov cyclization accounts for the indene 2 formation through an intermediate species such as F.…”

“…[11] In this regard, related 2-indenyl sulfides were obtained upon the reaction of allenes with electrophilic sulfur sources like thiosuccinimides in the presence of diphenyl selenide as a catalyst. [12] Electrophilic iodocarbocyclization reactions [13] have emerged as valuable strategies for constructing iodofuntionalizated indene scaffolds from a diverse range of starting materials. [14] Inspired by these precedents, we hypothesized that propargylic sulfides could react with a suitable iodonium source triggering sulfur migration and causing a subsequent carbocyclization giving rise to indene-containing β-iodoalkenyl sulfides which could be useful building blocks for assembling polycyclic scaffolds like indenobenzothiophene core which possess relevant applications in material science.…”

Trifluoromethylthiolation/Selenolation and Lactonization of 2-Alkynylbenzoate: The Application of Benzyl Trifluoromethyl Sulfoxide/Selenium Sulfoxides as SCF3/SeCF3 Reagents

“…In the presence of the electrophilic species, either the carbonyl group (Figure A, pathway a) or the triple bond (Figure A, pathways b and c) could be activated for cyclization. We first examined pathway a, in which the carbonyl group of o -alkynylbenzoate was initially activated by Tf 2 O, and the six-membered intermediate IV was formed via allene III as an important intermediate . However, on optimization, both III and IV underwent ring opening to structures similar to II .…”

Synthesis of Trisubstituted Chromanes by Lewis-Base-Catalyzed Three-Component Electrophilic Thiofunctionalization of Cyclopropene with Phenols via a Formal [3 + 3] Annulation

“…Alkene sulfenofunctionalization is a powerful strategy for the efficient introduction of sulfur moieties into organic molecules . Elegant works by Zhao and Denmark groups extended the concept of Lewis base activation of Lewis acids, enabling the sulfenofunctionalization of alkenes and enol ethers and, more recently, 1,2-cumulene . To our knowledge, however, the related process of cyclopropene is unknown.…”