Palladium-catalyzed modular assembly of electron-rich alkenes, dienes, trienes, and enynes from (E)-1,2-dichlorovinyl...

We have devised a modular construction of electron-rich alkene derivatives from trichloroethylene (TCE). The three C-Cl bonds of TCE have sufficiently different reactivities that they can be sequentially and selectively functionalized. Following the substitution of one chlorine by phenol to generate (E)-1,2-dichlorovinyl ether, the C(1)-Cl group next participates in palladium-catalyzed cross-coupling reactions with a variety of organometallic reagents. Subsequently, the C(2)-Cl group can engage in cross-couplings, while the C(2)-H may be deprotonated and quenched with an electrophile. Thus, isomerically pure tri- and tetrasubstituted electron-rich alkenes may be accessed in as few as two steps from simple and inexpensive starting materials. This method is ideally suited for diversity-oriented synthesis of highly conjugated molecules of interest as chromophores or as potential molecular electronics. It also gives access to diverse building blocks for further synthetic elaboration into high-value compounds.