Cover Picture: Synthesis of Phenylacetylene Dendrimers Having Sterically Congested Diazo Units and Characterization of Their Photoproducts (Eur. J. Org. Chem. 14/2004)

Abstract

The cover picture shows a phenylacetylene dendrimer having 12 diazo units, from which a dodecakiscarbene is generated. Diazo functional groups are usually labile and hence cannot be used as building blocks to prepare more complicated poly(diazo) compounds. We have shown that a diphenyldiazomethane prepared to generate a persistent triplet diphenylcarbene is also stable and can be used as a building block to construct poly(diazo) compounds, which can generate high‐spin polycarbenes. Details are discussed in the article by H. Tomioka et al. on page 2991 ff.

Sonogashira Reaction on Quinolizium Cations

“…Since it was introduced 30 years ago, the Sonogashira palladium-catalyzed cross-coupling reaction has emerged as one of the most straightforward and powerful methods for the preparation of conjugated alkynes . The numerous modifications of the original protocol and the improvement of many aspects of the sp-sp 2 carbon bond formation have led to the wide applicability of this reaction in the synthesis of a variety of compounds,2a including different heterocycles, and have made it a useful method for the synthesis of building blocks employed in the preparation of shape-persistent macrocycles, molecular electronic devices, dendrimers, etc.…”