The Preparation, Lithium Aluminum Hydride Reduction, and Electronic Spectra of Halogen-substituted 3,4-Bis(diphenylmethylene)-cyclobutenes and -cyclobutanes

The title compounds were prepared, and their physical and chemical properties were investigated. The reduction of the cyclobutenes with lithium aluminum hydride afforded halogenfree cyclobutane. The mechanism of the reduction is discussed. The cyclobutenes showed their K-bands in a wavelength region ca. 100 nm shorter than in the cases of the corresponding cyclobutanes. Furthermore, the K-band of the cyclobutenes is comparable to that of 1-phenylbuta-1,3-diene. On the basis of the electronic spectral data, a puckered structure was postulated for the cyclobutenes.