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Syntheses, Structures and Conformational Dynamics of 1,3,5‐Tris(3″‐ethynylbiphenyl‐2′‐yl)benzene Derivatives
Author(s) -
Trawny Daniel,
Quennet Marcel,
Rades Nadine,
Lentz Dieter,
Paulus Beate,
Reissig HansUlrich
Publication year - 2015
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201500615
Subject(s) - chemistry , iodine monochloride , benzene , conformational isomerism , ring (chemistry) , reagent , derivative (finance) , medicinal chemistry , bipyridine , sonogashira coupling , crystallography , crystal structure , organic chemistry , molecule , palladium , iodine , catalysis , financial economics , economics
Following a route described by Müllen et al. we improved the preparation of 1,2,3‐tris(3″‐iodobiphenyl‐2′‐yl)benzene ( 4 ). During the required iododesilylation with iodine monochloride the unexpected formation of a mono‐chlorinated compound 6 as major product was observed, when an excess of the iodination reagent was employed. The reaction mechanism for the formation of this compound involving an oxidizing process is discussed. X‐ray crystallography of the subsequent alkynylated product 7 proves the location of the chlorine atom at the central benzene ring. The related compound 5 was likewise investigated by X‐ray analysis revealing a preferred solid‐state conformation (“2‐up‐1‐down”) different from that of the chlorinated compound (“propeller” conformation). Compound 7 showed remarkable conformational dynamics in solution as observed by 1 H NMR spectroscopy. Temperature‐dependent measurements allowed the calculation of an energy difference of two major conformers of ca. 2 kJ/mol and a rotational barrier Δ G rot of ca. 77 kJ/mol. These values were convincingly confirmed by DFT calculations. A subsequent Sonogashira reaction of 4 with a suitable bipyridine derivative provided a unique trivalent bipyridine derivative.