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Hydrazide‐Catalyzed Polyene Cyclization: Asymmetric Organocatalytic Synthesis of cis ‐Decalins
Author(s) -
Plamondon Samuel J.,
Warnica Josephine M.,
Kaldre Dainis,
Gleason James L.
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201911952
Subject(s) - polyene , enantioselective synthesis , chemistry , catalysis , bicyclic molecule , stereochemistry , ring (chemistry) , organocatalysis , organic chemistry
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.