Highly Diastereoselective Synthesis of 1-Pyrrolines via SnCl₄-Promoted [3 + 2] Cycloaddition between Activated Donor–Acceptor Cyclopropanes and Nitriles

Abstract

Activated donor-acceptor cyclopropanes underwent formal [3 + 2] cycloaddition with nitriles in the presence of SnCl(4). The product 1-pyrrolines were isolated as single cis-diastereomers in moderate to good yields.

Stronger Brønsted Acids: Recent Progress

“…86 The [3 + 2] cycloaddition reaction of cyclopropanes with nitriles is a useful method for the preparation of 1-pyrrolines. 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).…”

Synthetic Applications of Aroyl‐ and Nitro‐substituted 2‐Aryl‐Cyclopropane‐1,1‐Dicarboxylates

“…With non‐lactonized substrates prepared by intermolecular cyclopropanation, the reaction could not be stopped at the 1‐pyrroline stage and further structural transformation occurred spontaneously to yield pyrroles . First, we decided to examine aroyl‐substituted D‐A cyclopropanes 1 as the 1,3‐dipole precursors for cycloaddition reactions with nitriles . It is obvious that these cyclopropanes possess a gem ‐diester moiety which would prevent any further spontaneous structural transformation in the expected 1‐pyrrolines.…”

“…nitriles 15 in the presence of 1 equiv. SnCl 4 in 1,2‐dichloroethane at room temperature, 1‐pyrrolines 16 were produced as single cis ‐diastereomers in yields ranging from 48–90 % (Scheme ) …”

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].…”