Combining aromaticity and strain with Tetsuo Nozoe--a passage of time with friends.

Note from the Editor: Tetsuo Nozoe lived his entire life on one of several island nations (Japan and Formosa, subsequently Taiwan, then returning to Japan). Those of us--and that is most of us!--who have never lived on an island nation likely cannot completely appreciate the 'isolation' and 'lack of diversity' that accompanies--along with many other valuable and happy consequences--such a life experience. As a New Zealander, colloquially as a Kiwi, Brian Halton shares this life experience with Nozoe. Indeed, New Zealand is far more isolated than either Japan or Taiwan in terms of distance to its nearest neighbor, population density, and size of its chemical community. Often during his career, Halton travelled to foreign lands, as did Nozoe, to fill his cup with collegiality and science. And Halton welcomed visitors to his beautiful country, as did Nozoe. Indeed, their mutual friendship was a blessing and honor to each of them. As Brian Halton tells his story of place and of science, I can well imagine Tetsuo Nozoe's response if he could read these words. He surely would have beamed in understanding these shared experiences!--Jeffrey I. Seeman Guest Editor University of Richmond Richmond, Virginia 23173, USA E-mail: jseeman@richmond.edu.

A Cyclopropabenzenylidenethenone (propadienone) via a new route to alkylidenecycloproparenes.

Reaction of 1,1-dichloro-2,5-diphenylcyclopropabenzene 6 with Meldrum's acid 8 in the presence of pyridine leads to coupling of the cycloproparenyl cation 7 with the stabilized diketo anion 9. Subsequent, spontaneous, base-induced dehydrochlorination gives the alkylidenecyclopropabenzene 11 in a one-pot reaction. Flash vacuum thermolysis of 11 at 650 degrees C ejects acetone and carbon dioxide, giving cyclopropabenzenylidenethenone 12 that is isolated in an Ar matrix at 20 K and characterized by a strong ketene band at 2107 cm(-1) in the IR spectrum. [reaction: see text]

C6H4 valence bond isomers: a reactive bicyclopropenylidene.

[reaction: see text] The simple bicyclopropenylidene derivative 21b, stabilized by fusion into naphthalene, results from reaction of dimesitylcyclopropenone 20b with the 1-trimethylsilyl-1H-cyclopropa[b]naphthalenyl anion. Although unstable in air, the molecule survives ambient conditions long enough for separation and mass spectral characterization. Aerial oxidation of 21b leads to 2,3-dimesitylanthracene-1,4-dione 22b whose X-ray crystal structure has been determined. While diphenylcyclopropenone 20a does not give identifiable products, the di-tert-butyl analogue 20c gives quinone 22c but in lower yield.

Synthetic protocols, molecular polarity, and 13C NMR correlations for 1-aryl- and 1-diarylmethylidene-1H-cyclopropa[b]naphthalenes.

The Peterson olefination for alkylidenecycloproparene synthesis from a 1,1-disilylcycloproparene has been refined into five distinct protocols that have provided 43 new aryl- (5 and 6) and diaryl- (7 and 8), and aryl(phenyl)- (9 and 10) methylidene derivatives. The permanent dipole moments of these and other previously reported compounds have been measured and the direction of the dipole, to or from the cycloproparenyl moiety, established for each compound. The 13C NMR spectra are fully assigned and linear correlations of carbon chemical shift with the Hammett sigmap+ constants for each atom within the cycloproparene moiety are provided for the 8-11 compounds that comprise each substitution pattern present in 5-10.

Diphenylmethylidenecyclobuta[a]cyclopropa[d]benzene: synthesis and spectral characterization.

[reaction: see text] The first derivative of the novel and highly strained rocketene (cyclobuta[a]cyclopropa[d]benzene) 5, namely, the C4 diphenyl-substituted exocyclic alkene 8, has been prepared in 16% overall yield as a yellow oil with properties fully consistent with its highly strained nature.