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Oligoene‐Based π‐Helicenes or Dispiranes? Winding up Oligoyne Chains by a Multiple Carbopalladation/Stille/(Electrocyclization) Cascade
Author(s) -
Milde Bastian,
Leibeling Markus,
Hecht Alexander,
Jones Peter G.,
Visscher Arne,
Stalke Dietmar,
Grunenberg Jörg,
Werz Daniel B.
Publication year - 2015
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.201501797
Subject(s) - helicene , racemization , stille reaction , steric effects , domino , chemistry , pfaffian , cascade , stereochemistry , computational chemistry , molecule , mathematics , combinatorics , polymer , organic chemistry , chromatography , catalysis
Abstract A domino approach consisting of up to five consecutive steps to access either highly substituted dispiranes or π‐helicenes from oligoyne chains is reported. The domino sequence consists of several carbopalladation reactions, a Stille cross‐coupling to obtain the helicenes, and, depending on the steric demands of the helicene, a final 6π‐electrocyclization to afford the dispiranes. Formally, the latter transformation contravenes the Woodward–Hoffmann rules, as revealed by X‐ray crystallography of the dispirane. Additionally, the racemization barrier of the ( Z , Z , Z )‐triene‐based helicene has been determined by a kinetic analysis and compared with results from density functional theory calculations. Characteristic points on the reaction coordinate were further analyzed according to their relaxed force constants (compliance constants).