The Fritsch–Buttenberg–Wiechell rearrangement: modern applications for an old reaction

Abstract

The Fritsch-Buttenberg-Wiechell rearrangement of carbene/carbenoid intermediates has evolved into a valuable synthetic methodology for the preparation of polyyne structures. Various synthetic routes toward the formation of the corresponding precursors, alkynyl-substituted dibromoolefins, have been developed. Additionally, the scope of this methodology is expanded significantly by the development of functional group-tolerant one-pot procedures. The preparation of various polyynes up to the octa- and decaynes is, thus, possible on a scale that enables thorough physico-chemical characterization. Hence, series of polyynes have been investigated by, e.g., UV-vis, IR- and Raman spectroscopy, as well as X-ray crystallography. These investigations give unique insight into the structural characteristics of longer polyynes and hint to the structure of carbyne.

The Synthesis of Functionalised Diaryltetraynes and Their Transport Properties in Single‐Molecule Junctions

“…Shorter chains of multiple conjugated alkyne units (i.e., diynes, oligoynes and polyynes), which possess terminal substituents to enhance their solubility and stability, have been studied for many years 5. They are fundamentally important molecules for experimental6–9 and theoretical studies10, 11 of conjugation and charge‐transport through carbon‐rich backbones.…”

Absolute Raman intensity measurements and determination of the vibrational second hyperpolarizability of adamantyl endcapped polyynes

“…Thus, although polyynes terminated with hydrogen or nitrogen atoms can be reasonably stable when dissolved in suitable solvents at high dilution, stability is quickly lost upon concentration of the solution . When endcapped by bulky groups, however, stabilized polyynes are formed, and polyynes as long as 44 contiguous sp‐hybridized carbon atoms have been synthesized and studied …”

Adamantyl‐endcapped polyynes

“…In spite of their simple structure, much remains unknown about the synthesis and properties of polyynes. Studies over the past decade have begun to unravel some aspects of polyyne chemistry, taking over from work of pioneers such as Walton, Jones, and Bohlmann in the 1950s, 1960s, and 1970s . Synthetic achievements have provided polyynes with unprecedented lengths and structure, whereas their physical characteristics have been analyzed in detail through, for example, Raman spectroscopy, nonlinear optical analyses, X‐ray crystallography, and theoretical studies …”