The cyclopropa[b]naphthalene electron donor: nonplanar 8π 7C cycloheptatrienylidene derivatives

Studies in the Cycloproparene Series: Cross‐Conjugated π‐Extended Alkylidenecycloproparenes

“…As expected, [21] 5 and 6 (1.38 and 1.88 D) are more polar than the diphenyl congeners 3 and 4 (0.44 and 1.19 D), respectively; HF/6-31G** calculations predict that the direction of the dipole lies from the cycloproparene moiety toward the exocyclic substituents. The fact that the diethers 4 [2] and 6 have an increased dipole moment relative to their non-ether counterparts 3 [6] and 5, respectively, [21] provides further experimental verification that the cyclopropa[b]naphthalenyl moiety is an electron donor. The degree of twisting of the terminal (C-5Ј) phenyl groups in 5 and 6 mirrors those in simple (E)-stilbenes [22] in that the twist angle is about 18°.…”

The Fulvalenes

“…[44] Recent experimental findings confirm the donation of electrons from the three-membered ring. [177] The electronic state properties have been assessed, [83] and a variety of derivatives including the exploded quinonoid derivative 128 were studied as early as 1975. [178] The first derivatives obtained were ones in which the larger ring was able to provide an appropriate electron sink with charge separation favouring the cyclopropenyl cation.…”

“…The extent of this depends upon electron donation -the stronger electron donating ether 139 is bent more than hydrocarbon 136 ( Figure 3) indicating a resistance to the development of 8π antiaromaticity in the cycloheptatrienylidene moiety. [177] Figure 3. Superimposed side perspectives of the triaheptafulvalenes 136 (broken lines) and 139 (solid lines) (reprinted from ref.…”

“…Superimposed side perspectives of the triaheptafulvalenes 136 (broken lines) and 139 (solid lines) (reprinted from ref. [177] with permission, copyright 2004, Elsevier).…”

Combining Aromaticity and Strain with Tetsuo Nozoe—A Passage of Time with Friends

“…Because of this, electron pair donation to the 6π cycloheptatrienylidene moiety creates an unfavourable antiaromatic 8π7C ring and this distorts from planarity for stabilization. [20] It served to remind me of Nozoe's life-long fascination with the sevenmembered ring and the tropolones in particular. Apart from the properties of all these compounds being duly assessed, extensions eventually took us to the cyclobutacyclopa derivative rocketene 22, [21] and the propadienone 23 that has transient existence even at low temperatures.…”