Parallel mechanisms for the cycloaromatization of enyne allenes †
作者:Thomas S. Hughes、Barry K. Carpenter
DOI:10.1039/a904369a
日期:——
The Myers–Saito cycloaromatization of enyne allenes is proposed to consist of two parallel mechanisms, one involving a biradical and the other with dipolar character. MCSCF calculations suggest that a nonplanar cyclic allene could be fairly close in enthalpy to the biradical, while the planar zwitterion originally proposed as a possible second intermediate is in fact a transition state for the interconversion
Synthesis of [<i>n</i>]- and [<i>n</i>.<i>n</i>]Cyclophanes by Using Suzuki−Miyaura Coupling
作者:Beverly B. Smith、Darron E. Hill、T. Ashton Cropp、Rosa D. Walsh、David Cartrette、Sherry Hipps、Amy M. Shachter、William T. Pennington、William R. Kwochka
DOI:10.1021/jo025509m
日期:2002.7.1
Reaction of the bis-9-BBN adduct of several dienes with 1,3-dibromobenzene via Suzuki coupling leads to a series of [n]metacyclophanes ranging in size from 10 to 17 atom members. In each case, two carbon-carbon bonds are formed in one reaction vessel. However, when the bis-9-BBN adduct of 1,5-hexadiene is coupled with a variety of aryl dihalides, larger [n.n]cyclophanes were formed in preference to the [n]cyclophanes. Four carbon-carbon bonds are formed in this instance. Single-crystal X-ray analyses of these [n.n]cyclophanes reveal interestingly shaped molecules with large cavities.
One-step preparation of metacyclophanes and (2,6)pyridinophanes by nickel-catalzyed Grignard cyclocoupling