Untersuchungen zur Stabilität und Reaktivität von (3‐Cyclopropylidenprop‐1‐enyl)‐ethyl‐ether

Abstract

~~~ ~ Stability and Reactivity of 3-Cyclopropylideneprop-1-enyl Ethyl Ether3-Cyclopropylideneprop-1-enyl ethyl ether (1) dimerizes to a cyclobutane derivative 2 which, upon prolonged heating, is converted to a cyclooctadiene (3). The reactivity of 1 is discussed. The structures of 2 and 3 as well as of their derivatives have been determined using 'H-NMR spectroscopy and X-ray crystal-structure analysis.

Synthesis and Properties of 2,3‐Diethynyl‐1,3‐Butadienes

“…Whereas catalyzed [4+4]‐cyclodimerizations of 1,3‐butadienes are well established, heat‐promoted processes are much rarer events, and heat‐promoted, concerted pericyclic [4+4]‐cycloadditions are disallowed by the Woodward–Hoffmann rules . We suspect that [4+4]‐cyclodimers of DEBDs are either the products of a stepwise biradical mechanism or the result of [2+2]‐cyclodimerization/Cope rearrangement . Diels–Alder dimers 18 and 19 were found to decompose on prolonged heating, which explains the absence of the [4+2]‐cycloadduct from the product mixtures analyzed by the Hopf group.…”