An Evolving Multifunctional Molecular Building Block: Bicyclopropylidene

Abstract

The elucidation of the chemistry of the highly strained and unusually tetrasubstituted alkene bicyclopropylidene (2), has proved to be fruitful, both with respect to synthetic applications as a multifunctional C 6 building block and for the understanding of certain reaction principles. The different, and steadily improved, methods developed over the last thirty years for the preparation of this unusual alkene, and the more recent methods for the synthesis of functionally substituted as well as spirocyclopropanated derivatives, are presented. The rich chemistry of bicyclopropylidene, beginning with its well-known thermal rearrangement and dimeriz-[a] and books. His scientific achievements have been published in over 420 original publications, review articles, and chapters in books. His current research interests include the development of new cascade reactions for the efficient construction of complex skeletons and new small-ring building blocks to be applied in the synthesis of natural and nonnatural compounds, new highly strained polycyclic compounds with interesting properties, as well as the development of new synthetic methodology based on metal-mediated and -catalyzed transformations of organic compounds.

Synthesis of Spiro[2.2]pentanes and Spiro[2.3]hexanes Employing the Me3Al/CH2I2 Reagent

“…It is known that the relatively bulky zinc carbenoid impedes the cyclopropanation of sterically hindered alkenes. Bicyclopropylidenes and bicyclobutylidenes showed low reactivity towards zinc carbenoids , . [3]Triangulane was obtained in 5–15 % yield by using Zn/Cu and Zn/Ag couple from vinylidenecyclopropane .…”

Interatrial defect sizing by intracardiac and transesophageal echocardiography compared with fluoroscopic measurements in patients undergoing percutaneous transcatheter closure

“…In particular, systems containing olefinic moieties present a challenging class of compounds as their reactivity involves a variety of interesting reactions, creating a multitude of unusual structures. Bicyclopropylidene ( BCP ) serves as a sophisticated example in which two cyclopropylidene rings are connected by a shared carboncarbon double bond 2.…”

Cyclopropylidenes, bicyclopropylidenes, and vinylcarbenes — some modes of formation and preparative applications

“…13 Bicyclopropylidene (3) is also the key intermediate en route to perspirocyclopropanated (second generation) bicyclopropylidene 4, the third generation bicyclopropyl idene 5 and perspirocyclopropanated [3] The latter alkene, which had previously been pre pared by Fitjer, 23 can be extended to allene 22 by the Doering-Skattebøl-Moore protocol, i.e., dibromo carbene addition and treatment of the resulting di bromocyclopropanation product with methyllithium in ether (Scheme 3). 24 Upon cyclopropanation of 22 with in situ generated diazocyclopropane, perspirocyclopropanated bicyclo propylidene 4 was obtained in 35% yield along with regioisomeric cyclopropanation product 23 and tetraspiro cyclopropanated [3]rotane 24, a branched [8]triangulane, resulting from twofold cyclopropanation of allene 22 with diazocyclopropane. 24,25 Perspirocyclopropanated bicyclopropylidene 4 served as the starting material for perspirocyclopropanated [3]rotane, D 3h symmetric branched [10]triangulane 2.…”

“…For the same reason, the yet unknown cyclo [8]tri angulane 6 should be an isolable molecule in spite of its extrapolated strain energy of 292 kcal mol -1 . The ring opening of, e.g., an external cyclopropane bond in 6 would also require about the same activation energy, but once this would have happened to give 1,3 diradical 32, the molecule would rapidly unzip to [8]radialene 33 (see Scheme 5).…”

“…3-5 For bicyclopropylidene (3), this has been demonstrated in a number of ways 6-9 and even quantified by the kinetics of its bromination. 10 Our own first synthesis of 3 8 was not much better than the first published synthesis by Conia et al, 11 but -after a number of improvements had been made by Conia et al and by our group 12eventually we were able to develop a really produc tive synthesis of this unique C 6 H 8 hydrocarbon, which is easily reproducible and also scalable to multikilo gram quantities. 13 In the meantime, we have created ac cesses to the second generation bicyclopropylidene 4 and even the third generation derivative -speaking in terms of dendrimers -5.…”