Silver‐Catalyzed Double Hydrocarbonation of 2‐Trifluoromethyl‐1,3‐Conjugated Enynes with 1,3‐Dicarbonyl Compounds: Synthesis of Ring‐Trifluoromethylated Cyclopentene

Abstract

An unexpected atom-economic tandem intermolecular hydrocarbonation and intramolecular hydrocarbonation (double hydrocarbonation sequence) of 2-trifluoromethyl-1,3-conjugated enynes with 1,3-dicarbonyl compounds leading to ring-trifluoromethylated cyclo-pentene frameworks by combination use of AgNO 3 as a catalyst and Et 3 N as a base was developed. Enynes possessing electron-withdrawing aryl groups on the alkyne moiety are general good candidates for present transformation.

Synthesis of Trifluoromethylated Pyrazolidines, Pyrazolines and Pyrazoles via Divergent Reaction of β-CF3-1,3-Enynes with Hydrazines

“…enynes bearing electron-withdrawing aryl group on the alkyne moiety are generally good reaction partners for the present transformation, and the desired trifluoromethylated pyrazolines could be obtained in moderate to excellent yield; the electron-withdrawing group on the alkyne moiety can facilitate the allene intermediate formation accounting for this phenomenon …”

“…To assess the generality of this reaction, we tested a range of β-CF 3 -1,3-enynes 1 and sulfonyl hydrazines 2 (Scheme ). There are some points to note: enynes bearing electron-withdrawing aryl group on the alkyne moiety are generally good reaction partners for the present transformation, and the desired trifluoromethylated pyrazolines could be obtained in moderate to excellent yield; the electron-withdrawing group on the alkyne moiety can facilitate the allene intermediate formation accounting for this phenomenon Enynes bearing substituents at the meta - or ortho -positions of aryl group on the alkyne moiety were also amenable to the reaction conditions, providing the desired products in moderate to good yields ( 3h – 3j ). As for aryl sulfonyl hydrazines reaction partners, electronic and steric effects have dramatic influence on this annulation, as evidenced by the formation of pyrazolines 3k – 3u .…”

“…Double Hydroamination Reaction of β-CF 3 -1,3enynes with Primary Amines and Hydrazines alkyne moiety can facilitate the allene intermediate formation accounting for this phenomenon. 10 (2) Enynes bearing substituents at the meta-or orthopositions of aryl group on the alkyne moiety were also amenable to the reaction conditions, providing the desired products in moderate to good yields (3h−3j). (3) As for aryl sulfonyl hydrazines reaction partners, electronic and steric effects have dramatic influence on this annulation, as evidenced by the formation of pyrazolines 3k−3u.…”

Synthesis of Fluoroalkyl Cyclopentenes: Highly Diastereoselective Phosphine‐Catalyzed [3+2] Annulation of β‐Fluoroalkylvinyl Arylsulfones with Morita‐Baylis‐Hillman Carbonates

“…In 2017, Zhang, Xiao and co-workers reported a silver-catalyzed tandem CÀ C/CÀ C bond forming reaction to generate 1-trifluoromethylated cyclopentene (Scheme 1a). [10] In 2012, utilizing axially chiral multifunctional thiourea-phosphines as catalysts, Shi and co-workers developed asymmetric [3 + 2] annulation of trifluoroethylidene-malonates with Morita-Baylis-Hillman (MBH) carbonates, affording chiral trifluoromethylated cyclopentenes (Scheme 1b). [11] In 2020, Lu, Ding and co-workers disclosed a [3 + 2] annulation between 3butynoates and β-trifluoromethyl enones through an amine-phosphine binary catalytic system to furnish chiral 3trifluoromethylated cyclopentenes (Scheme 1c).…”

“…However, only limited related methods were reported. In 2017, Zhang, Xiao and co‐workers reported a silver‐catalyzed tandem C−C/C−C bond forming reaction to generate 1‐trifluoromethylated cyclopentene (Scheme 1a) [10] . In 2012, utilizing axially chiral multifunctional thiourea‐phosphines as catalysts, Shi and co‐workers developed asymmetric [3+2] annulation of trifluoroethylidene‐malonates with Morita‐Baylis‐Hillman (MBH) carbonates, affording chiral trifluoromethylated cyclopentenes (Scheme 1b) [11] .…”