TfOH-Catalyzed Formal [3 + 2] Cycloaddition of Cyclopropane 1,1-Diesters with Nitriles

Abstract

A triflic acid-catalyzed formal [3 + 2] cycloaddition of cyclopropane 1,1-diesters with nitriles was developed. This reaction was expeditious, and the scope of the substituents in both cyclopropanes and nitriles was broad. This supplies an efficient and practical method for the synthesis of 1-pyrrolines.

Stronger Brønsted Acids: Recent Progress

“…Although Lewis-acid-catalyzed reactions have been reported, 87,88 Wang and co-workers developed a Brønsted-acid-catalyzed formal [3 + 2] cycloaddition reaction of cyclopropane 1,1-diester 68 with benzonitriles. 89 Enantiopure substrate 70 (99% ee) underwent the [3 + 2] cycloaddition to furnish adduct 71 with slight racemization (73% ee) (Scheme 22). This result suggests that the present reaction proceeded by a S N 2 mechanism in which a Ritter nitrilium intermediate 72 was involved.…”

Synthesis of new tricyclic 5,6-dihydro-4H-benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepine derivatives by [3+ + 2]-cycloaddition/rearrangement reactions

“…In this pathway, the reaction is initiated by AlCl 3 coordination with the acetate moiety of 8a to generate the azocarbenium ion 14 as a reactive intermediate, which cannot be isolated by now [31]. Then, the nitrogen atom of the nitrile approaches to the central electron-deficient carbon atom in 14 to form a Ritter-type nitrilium salt 15 [48]. Salt 15 then undergoes a concerted but asynchronous cyclization [49] to afford the initial spiro-substituted adduct 16 , which has a strong proclivity for ring expansion to occur.…”

Synthesis and Reactivity of Donor-Acceptor Substituted Aminocyclopropanes and Aminocyclobutanes

“…Their unique reactivity and their combination with various 1,3 formal dipoles gave access to diverse structures such as pyrrolines [116][117][118][119][120][121][122] or pyrroles [123][124][125][126][127]. Their unique reactivity and their combination with various 1,3 formal dipoles gave access to diverse structures such as pyrrolines [116][117][118][119][120][121][122] or pyrroles [123][124][125][126][127].…”