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Structural Parameters and Electronic Interactions in Substituted 1,1‐Diethynylcyclopropanes − An Experimental Study
Author(s) -
de Meijere Armin,
Kozhushkov Sergei I.,
Boese Roland,
Haumann Thomas,
Yufit Dmitrii S.,
Howard Judith A. K.,
Khaikin Leonid S.,
Trætteberg Marit
Publication year - 2002
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(20022)2002:3<485::aid-ejoc485>3.0.co;2-7
Subject(s) - cyclopropane , chemistry , trimethylsilyl , diacetylene , silylation , carbene , crystal structure , acetylene , heptane , ethylene , bond length , medicinal chemistry , triple bond , yield (engineering) , stereochemistry , crystallography , ring (chemistry) , double bond , organic chemistry , catalysis , polymerization , polymer , materials science , metallurgy
1,1‐Bis(trimethylsilylethynyl)cyclopropane ( 4 ) and dimethyl 3,3′‐(1,1‐cyclopropanediyl)bis(2‐propynoate) ( 5 ) have been prepared by silylation of the known 1‐(bromoethynyl)‐1‐(trimethylsilylethynyl)cyclopropane ( 7 ) and by double carboxylation of 1,1‐diethynylcyclopropane ( 3 ) followed by esterification, in 91 and 74% overall yields, respectively. 7,7‐Diethynyldispiro[2.0.2.1]heptane ( 6 ) has been synthesized from ethyl dispiro[2.0.2.1]heptane‐7‐carboxylate ( 9 ) by a ten‐step sequence in 41% overall yield. Upon UV irradiation, the diacetylene 4 underwent ethylene extrusion, and the resulting bis(trimethylsilylethynyl)carbene dimerized with electron reorganization to give 1,4,8‐tris(trimethylsilyl)‐3‐(trimethylsilylethynyl)oct‐3‐ene‐1,5,7‐triyne ( 20 ) (24% yield). X‐ray crystal structure analyses of 4 , 5 , and 6 revealed strong electronic interactions between the acetylene fragments and the cyclopropane rings, but no homoconjugative effects between two ethynyl fragments on the same cyclopropane ring of either compounds 4 and 5 , as the bond lengths in the C≡C−C−C≡C fragments were exactly the same in both molecules and very close to those in unsubstituted 1,1‐diethynylcyclopropane ( 3 ). A gas‐phase electron‐diffraction structure analysis of 4 revealed triple bonds significantly longer [1.240(1) Å] than those found by crystal structure analysis [1.205(2) Å]. The observed shortening of the triple bonds in the dispiro[2.0.2.1]heptane derivative 6 [1.187(3) Å] relative to those in 4 and 5 [1.205(2) Å], as well as the slight increase in the angle α between the geminal ethynyl groups, are probably due to the different hybridization in the central ring of 6 .