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Pyramidalization in Derivatives of Bicyclo[5.1.0]oct‐1(7)‐enes and 2,2,5,5‐Tetramethylbicyclo[4.1.0]hept‐1(6)‐enes
Author(s) -
Irngartinger Hermann,
Altreuther Annegret,
Sommerfeld Thomas,
Stojanik Torsten
Publication year - 2000
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 - 10.1002/1099-0690(200012)2000:24<4059::aid-ejoc4059>3.0.co;2-v
Subject(s) - cyclopropene , chemistry , bicyclic molecule , ring (chemistry) , ring strain , ab initio , lone pair , stereochemistry , ab initio quantum chemistry methods , cyclohexane conformation , cyclopropane , computational chemistry , ring size , crystallography , hydrogen bond , molecule , medicinal chemistry , organic chemistry
Bicyclo[4.1.0]hept‐1(6)‐ene and bicyclo[5.1.0]oct‐1(7)‐ene systems have been investigated by X‐ray diffraction and ab initio methods. The syntheses of 3b−3e , 4a , 4b , 6a , 7a , 8b , 9b , 12 , 13 , and 16 have been described and the structures of 1 , 3a , 4b , 5a , 7a , 10 , 11 , and 13−16 have been determined by X‐ray analysis. To complement these experimental data, several model compounds have been studied theoretically. For the cyclopropenes 14 and 15 , substantial pyramidalization has been observed, and the six‐membered ring species is considerably more strongly deformed than the seven‐membered ring system [ 14 : Φ = 14.5(6)°; 15 : Φ = 30.2(5)°]. Our analysis, with the aid of the model compounds M‐3.OH , M‐63.H , M‐63.OH , M‐73.H , and M‐73.OH , clearly shows that the decisive factors for pyramidalization are ring size, conformation, and repulsion between the occupied π bond and the oxygen lone pairs. The last factor contributes to the pyramidalization stemming from ring strain in 14 and is the dominant source of deformation in 15 . In the cyclopropenylidene systems 4b [Φ = 0.7(4)°], 11 [Φ = 1.1(3)°], 13 [Φ = 4.7(5)°], and 1 [Φ = 7.9(5)°], we have studied the electronic influence on pyramidalization. A high degree of pyramidalization is favored by weak cyclopropenylium character, and cyclopropenylidenes exhibit, in general, smaller deformations than do analogous cyclopropene systems.