Hydrazide‐Catalyzed Polyene Cyclization: Asymmetric Organocatalytic Synthesis of cis‐Decalins. (21st November 2019)

• Record Type: Journal Article
• Authors: Plamondon, Samuel J.; Warnica, Josephine M.; Kaldre, Dainis; Gleason, James L.
• Is Part Of: Angewandte Chemie. Volume 132:Number 1(2020)
• Page Start: 259
• Page End: 264
• Publication Date: 2019-11-21
• Subjects: Asymmetrische Katalyse -- cis-Decalin -- Hydrazid -- Organokatalyse -- Polyencyclisierung; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201911952
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Polyene cyclizations offer rapid entry into terpenoid ring systems. Although enantioselective cyclizations of ( E )‐polyenes to form trans ‐decalin ring systems are well precedented, highly enantioselective cyclizations of ( Z )‐polyenes to form the corresponding cis ‐decalins have not been reported. Here, we describe the first application of iminium catalysis to the initiation of polyene cyclizations. Ethyl 1, 2‐diazepane‐1‐carboxylate catalyzes the cyclization of polyenes bearing enal initiators. Moreover, chiral bicyclic hydrazides catalyze the cyclizations of ( Z )‐polyene substrates to form cis ‐decalins with enantioselectivities of up to 97:3 er. DFT calculations suggest the catalysts promote the reaction by stabilizing positive charge as it develops during the bicyclization. Abstract : Ferngesteuerte Stabilisierung : Chirale bicyclische Hydrazide katalysieren Cyclisierungen von ( Z )‐Polyenen zu cis ‐Decalinen mittels Iminiumionen‐Katalyse. Die hohe Enantioselektivität resultiert aus der Fernstabilisierung der entstehenden kationischen Ladung im Übergangszustand durch das Hydrazidcarbonyl.