Pnictogen-Bonding Catalysis: An Interactive Tool to Uncover Unorthodox Mechanisms in Polyether Cascade Cyclizations.

Miguel Paraja, Andrea Gini, Naomi Sakai, Stefan Matile

Chemistry (Weinheim an der Bergstrasse, Germany) 2020 Dec 01

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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 SN 2- to SN 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 SbV catalyst is used to demonstrate that this unorthodox polyether cascade cyclization mechanism occurs. © 2020 Wiley-VCH GmbH.

Citation

Miguel Paraja, Andrea Gini, Naomi Sakai, Stefan Matile. Pnictogen-Bonding Catalysis: An Interactive Tool to Uncover Unorthodox Mechanisms in Polyether Cascade Cyclizations. Chemistry (Weinheim an der Bergstrasse, Germany). 2020 Dec 01;26(67):15471-15476