From diyls to ylides to my idyll.

Chemical research and mountaineering have much in common. If the goal or the summit is to be reached, both initiative and determination as well as perseverance are required. But after the hard work it is a great joy to be at the goal or the peak with its splendid panorama. However, especially in chemical research as far as new territory is concerned the results may sometimes be quite different: they may be disappointing or delightful. Looking back at my work in scientific research, I will confine this talk to the positive results (1). Some 50 years ago I was fascinated by an idea which I investigated experimentally. The question was how ring strain acts on a ring if an accumulation of phenyl groups at two neighboring carbon atoms weakens the C-C linkage and predisposes to the formation of a diradical (for brevity called diyl) (Fig. 1). Among the many experimental results (2) I choose the synthesis of the hydrocarbons 1 and 4 (3), which we thought capable of diyl formation. Starting materials were appropriate dicarboxylic esters, which we transformed into the corresponding glycols. While these were obtained under the influence of phenylmagnesium halide only in modest yield, phenyllithium proved to be superior and was readily accessible by the method of K. Ziegler, using bromobenzene and lithium. The glycolates resulting from the reaction with potassium phenylisopropylide formed on heating with methyl iodide the corresponding dimethyl ethers, which supplied the equivalent hydrocarbons 1 and 4 by alkali metal splitting and demetalation with tetramethylethylene dibromide.