With finesse and strain: Highly strained derivatives of fenestranes, [4.6.4.6]fenestradienes, have been prepared using a remarkable reaction cascade featuring a 4‐exo‐dig cyclocarbopalladation, a Sonogashira‐type coupling, a regioselective alkynylation, and an 8π/6π electrocyclization sequence.
carbopalladation/Sonogashira coupling tandem reaction, and a subsequent P-2 Ni induced semi-hydrogenation. This leads to a first generation of cyclooctatrienes and [4.6.4.6]fenestradienes. Next, the second approach will be presented, in which the second generation of these compounds is accessed in a one-pot reaction including five steps, starting from the same alkenyl bromide compounds. These methods
Two new palladium catalyzed cascade reactions involving a 4-exo-dig cyclocarbopalladation are described. These processes are shown to convert bromoenediynes and bromodienynes into strained aromatic compounds in a single step.
The syntheses of new scaffolds containing small strained rings are described via an original domino reaction. The process works efficiently and selectively via 4-exo-dig/5- or 6-exo-trig/3-exo-trig cyclocarbopalladations followed by a β-hydride elimination. During this cascade, the palladium moves several times along the carbon structure for the creation of threenew C–C bonds and threenew rings.
Synthesis of [4.6.4.6]Fenestradienes and [4.6.4.6]Fenestrenes Based on an 8π−6π-Cyclization-Oxidation Cascade
作者:Catherine Hulot、Gaëlle Blond、Jean Suffert
DOI:10.1021/ja800691c
日期:2008.4.1
compounds of synthetic and theoretical interest are a class of tetracyclic skeletons, defined as doubly a,a'-bridged spiroalkanes. The reported results are focused on the synthesis of new and original [4.6.4.6]fenestradienes 3a-f and [4.6.4.6]fenestrenes 4a-e. Our approach implies the formation of this tetracyclic structure by a reaction cascade, based on consecutive transformations starting from the trienyne