Synthesis of Thio‐/Selenopyrrolines via SnCl₄‐Catalyzed (3+2)‐Cycloadditions of Donor‐Acceptor Cyclopropanes with Thio‐/Selenocyanates

Abstract

A straightforward protocol has been developed to access thio-/ selenopyrrolines through a (3 + 2)-cycloaddition of aryl thio-/ selenocyanates with donor-acceptor cyclopropanes (DACs) in the presence of SnCl 4 as a Lewis acid catalyst. Further, good chemoselectivity was observed when DACs were treated with 3-cyano phenyl thiocyanate. These results suggest that thiocyanate is more reactive than nitrile moiety in such (3 + 2)cycloaddition reactions.

Organic Selenocyanates: Rapid Advancements and Applicationsin the Field of Organic Chemistry

“…In 2021, Singh and coworkers accomplished tin chloride (IV)-catalyzed synthesis of various selenopyrroline derivatives 185 through (3 + 2)-cycloaddition reactions of donor-acceptor cyclopropanes(DACs) 183. [65] Under the optimized reaction conditions, a panel of electron-deficient and electron-rich substituted aryl selenocyanates (184 a-184 h) responded well to accomplish the selenopyrroline cycloadducts (185 a-185 h) in good to excellent yields. This conversion was suitable for a wide variety of functional groups, along with bromo, iodo, ester, nitro, and tert-butyl groups (184 b-184 g).…”

“…Because of the distinctive polarization of the electronically activated nitrile functional group of selenocyanates, this group of compounds is an appealing collaborator for cycloaddition reactions, resulting in a broadly substituted heterocyclic compounds. In 2021, Singh and coworkers accomplished tin chloride (IV)‐catalyzed synthesis of various selenopyrroline derivatives 185 through (3+2)‐cycloaddition reactions of donor‐acceptor cyclopropanes(DACs) 183 [65] . Under the optimized reaction conditions, a panel of electron‐deficient and electron‐rich substituted aryl selenocyanates ( 184 a – 184 h ) responded well to accomplish the selenopyrroline cyclo‐adducts ( 185 a – 185 h ) in good to excellent yields.…”

“…Without further optimization, this technique could be used to synthesize selenopyrroline on a gram‐scale (Scheme 86). [65] …”

Synthesis of Heterocycles from Donor-Acceptor Cyclopropanes: A Five-Year Recap

“…Review / Short Review 52 Both electron-deficient and electron-rich selenocyanates/thiocyanate reacted efficiently with the DAC to deliver the corresponding selenopyrrolines 107/thiopyrrolines 108 in good to excellent yields. It was observed that the thiocyanate moiety reacted faster than the nitrile moiety towards the DAC which was also proved experimentally.…”

“…Seleno- and thiopyrrolines of the type 107 and 108 were synthesized by Goswami and co-workers in 2021 by the (3+2) cycloaddition of aryl seleno- or thiocyanates 105 and 106 with DACs in the presence of SnCl 4 as Lewis acid catalyst (Scheme 23 ). 52 Both electron-deficient and electron-rich seleno- and thiocyanate reacted efficiently with DACs to deliver selenopyrrolines 107 and thiopyrrolines 108 , respectively, in good to excellent yields. It was observed that the thiocyanate moiety reacted faster than the nitrile moiety with the DAC, which was also proved experimentally.…”