Anionische Cycloaddition an elektronenarme Alkine – Synthese und Stereochemie von 3‐Pyrrolin‐3‐carbonsäure‐N,N‐dimethylamiden

Abstract

Einen Zugang zu 3‐Pyrrolin‐Derivaten wie (2) mit definierter räumlicher Anordnung der Substituenten an C‐2 und C‐5 eröffnet die Umsetzung von (1) mit elektronenarmen Alkinen. Verbindungen vom Typ (2) interessieren wegen ihrer biologischen Aktivität.

Mechanism of Anionic [3 + 2] Cycloadditions. An ab Initio Computational Study on the Cycloaddition of Allyl-, 2-Borylallyl-, and 2-Azaallyllithium to Ethylene

“…There are many examples involving olefins with aromatic and/or electron- withdrawing substituents. , Alkenes bearing organoelement groups containing Si, Ge, P, As, S, and Se have proved to be very useful extensions, 9bb,cc, since such substituents can easily be replaced by a large number of other functionalities. Cycloadditions with some dienes and alkynes, ,9bb, aromatic nitriles, and with CN, CS, and NN double bonds 9r,13 also have been reported.…”

“…An equally elegant access to pyrrolidine ring systems is provided by the cycloaddition of 2-azaallyl anions and olefins. Numerous examples of both reactions have been reported in the literature. − Frontier orbital considerations (the Woodward−Hoffmann rules) 15 predict that, for these reactions, a concerted 4π s + 2π s cycloaddition mechanism is symmetry-allowed (route A in Scheme ). Alternatively, a two-step pathway may be followed, involving pentenyl or azapentenyl anion intermediates (route B).…”

Gold(I)‐Catalyzed Cycloisomerization of 1,6‐Diynes: Synthesis of 2,3‐Disubstituted 3‐Pyrroline Derivatives

“…Nu = nucleophile. (21072206, 20472096, 20872162, 20672127, 20821002, and 20732008 [2][3][4][5][6][7][8][9]. As for substrate 1 k having a methyl group on the benzene ring (R 4 = CH 3 ) and R 2 and R 3 were methyl groups, the corresponding product 2 g was formed in 88 % yield (Table 2, entry 10).…”

Gold(I)‐Catalyzed Cycloisomerization of 1,6‐Diynes: Synthesis of 2,3‐Disubstituted 3‐Pyrroline Derivatives

“…[3f] We therefore anticipated that a new cascade process initiated by gold-induced CÀC bond formation along with cycloisomerization might be achieved in a system in which a nitrogen atom connects 1,6-diyne to give heterocyclic products (Z = N). Herein, we report a novel C À C bond formation along with cycloisomerization from 1,6-diyne-containing propargylic ester and arene-yne (arenyne) units toward nitrogen-containing fivemembered heterocyclic rings such as 2,3-disubstituted 3pyrrolines, [4] which have been extensively used as synthetic building blocks in organic synthesis and appear as structural motifs in many natural products, thus exhibiting interesting biological activities. [5] Initial studies using propargylic acetate arenyne 1 a (0.2 mmol) as the substrate were aimed at determining the reaction outcome and subsequently optimizing the reaction conditions.…”

“…Nu = nucleophile. [2][3][4][5][6][7][8][9]. As for substrate 1 k having a methyl group on the benzene ring (R 4 = CH 3 ) and R 2 and R 3 were methyl groups, the corresponding product 2 g was formed in 88 % yield (Table 2, entry 10).…”