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Scholl‐Type Cycloheptatriene Ring Closure of 1,4,9,12‐Tetraarylfenestrindanes: Reactivity and Selectivity in the Construction of Fenestrane‐Based Polyaromatic Saddles
Author(s) -
Wong WaiShing,
Lau WingWa,
Li Yuke,
Liu Zhifeng,
Kuck Dietmar,
Chow HakFun
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.201904949
Subject(s) - closure (psychology) , cycloheptatriene , ring (chemistry) , reactivity (psychology) , type (biology) , chemistry , geology , medicinal chemistry , organic chemistry , economics , medicine , paleontology , alternative medicine , pathology , market economy
Abstract The Scholl‐type cyclodehydrogenation, generating up to four cycloheptatriene rings around a fenestrindane core, leads to novel, saddle‐shaped polyaromatic hydrocarbon derivatives. In this article, we present the results of in‐depth experimental and computational work on the oxidative cyclization of various 1,4,9,12‐tetraarylfenestrindanes. In particular, the kinetic control of the four‐step cyclization of the electronically activated tetrakis(3,4‐dimethoxyphenyl) derivative is elucidated. The reasons for the exclusive emergence of one single among the three possible doubly cyclized intermediates and for the nonappearance of the singly and triply cyclized intermediates are clarified. In addition, the origin of the concomitant bridgehead hydroxylation is studied. The reactivity of a set of fifteen symmetrically and unsymmetrically substituted 1,4,9,12‐tetraarylfenestrindanes towards Scholl‐type cyclodehydrogenation is presented, pinpointing the structural factors that underlie this reaction and demonstrating the potential and limitations of this synthetic approach. A particularly surprising finding of this study is that the electronically nonactivated 1,4,9,12‐tetraphenylfenestrindane can also undergo the fourfold Scholl‐type cyclization process and can be transformed into the parent saddle hydrocarbon.