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Pnictogen‐Bonding Catalysis: An Interactive Tool to Uncover Unorthodox Mechanisms in Polyether Cascade Cyclizations
Author(s) -
Paraja Miguel,
Gini Andrea,
Sakai Naomi,
Matile Stefan
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202003426
Subject(s) - pnictogen , chemistry , stereochemistry , supramolecular chemistry , catalysis , epoxide , cascade , bond cleavage , organocatalysis , ring (chemistry) , crystallography , crystal structure , enantioselective synthesis , organic chemistry , physics , superconductivity , chromatography , quantum mechanics
Pnictogen‐bonding catalysis and supramolecular σ‐hole catalysis in general is currently being introduced as the non‐covalent counterpart of covalent Lewis acid catalysis. With access to anti‐Baldwin cyclizations identified as unique characteristic, pnictogen‐bonding catalysis appeared promising to elucidate one of the hidden enigmas of brevetoxin‐type epoxide opening polyether cascade cyclizations, that is the cyclization of certain trans epoxides into cis‐fused rings. In principle, a shift from S N 2‐ to S N 1‐type mechanisms could suffice to rationalize this inversion of configuration. However, the same inversion could be explained by a completely different mechanism: Ring opening with C−C bond cleavage into a branched hydroxy‐5‐enal and the corresponding cyclic hemiacetal, followed by cascade cyclization under conformational control, including stereoselective C−C bond formation. In this report, a pnictogen‐bonding supramolecular Sb V catalyst is used to demonstrate that this unorthodox polyether cascade cyclization mechanism occurs.