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Experimental Assessment of the Effect of a Bicyclo[1.1.0]butane System in Strain‐Induced Localisation of Aromatic π‐Bonds
Author(s) -
Cohrs Carsten,
Reuchlein Horst,
Musch Patrick W.,
Selinka Carola,
Walfort Bernhard,
Stalke Dietmar,
Christl Manfred
Publication year - 2003
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.200390137
Subject(s) - norbornane , chemistry , bicyclic molecule , methylene , moiety , norbornene , pyridazine , butane , stereochemistry , double bond , ring strain , medicinal chemistry , cyclopropane , organic chemistry , molecule , ring (chemistry) , monomer , catalysis , polymer
The geometrical parameters of the dimethyl pyridazine‐1,4‐dicarboxylates 13 − 16 , in which a σ‐bond system is annulated at the C5−C6 bond, have been determined by X‐ray diffraction. As compared to the cyclopentene subunit in 16 , which is believed to exert no significant influence on the bond lengths of the aromatic moiety, the norbornene, benzvalene, and bicyclo[2.1.1]hexene subunits of 13 − 15 , respectively, cause alternating bond elongations and shortenings in the pyridazine moiety, with increasing magnitudes, in that order. These effects are in line with the heats of the isodesmic reactions that convert norbornene ( 8 ), benzvalene ( 6 ), and bicyclo[2.1.1]hex‐2‐ene ( 4 ) with buta‐1,3‐diene into ethene as well as 2,3‐bis(methylene)norbornane ( 9 ), 3,4‐bis(methylene)tricyclo[3.1.0.0 2,6 ]hexane ( 7 ), and 2,3‐bis(methylene)bicyclo[2.1.1]hexane ( 5 ), respectively. Calculated originally by W. L. Jorgensen and W. T. Borden in the 1970s, the reactions have now been reexamined by employing much higher levels of theory. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)