A mild, palladium-catalyzed method for the dehydrohalogenation of alkyl bromides: synthetic and mechanistic studies.
We have exploited a typically undesired elementary step in cross-coupling reactions, β-hydride elimination, to accomplish palladium-catalyzed dehydrohalogenations of alkyl bromides to form terminal olefins. We have applied this method, which proceeds in excellent yield at room temperature in the presence of a variety of functional groups, to a formal total synthesis of (R)-mevalonolactone. Our mechanistic studies have established that the rate-determining step can vary with the structure of the alkyl bromide and, most significantly, that L(2)PdHBr (L = phosphine), an intermediate that is often invoked in palladium-catalyzed processes such as the Heck reaction, is not an intermediate in the active catalytic cycle.
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Alex C
AC
Bissember
Anna
A
Levina
Gregory C
GC
Fu
D000473:Alkanes / Q000737:chemistry*; D000475:Alkenes / Q000138:chemical synthesis*; D001966:Bromine / Q000737:chemistry*; D002384:Catalysis; D054879:Halogenation; D010165:Palladium / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry
D000473:Alkanes; D000475:Alkenes; D010720:Phosphines; D010165:Palladium; C044646:phosphine; D001966:Bromine