179320-40-2Relevant academic research and scientific papers
Cyclization versus Pd-H elimination-readdition: Skeletal rearrangement of the products of Pd-C6F5 addition to 1,4-pentadienes
Albéniz, Ana C.,Espinet, Pablo,Lin, Yong-Shou
, p. 7145 - 7152 (2007/10/03)
The reactions of [Pd(C6F5)Br(CH3CN)2] with 1,4-pentadiene or 3-methyl-1,4-pentadiene at low temperature afford, after insertion of one double bond into the Pd-C6F5 bond, two types of η1-η2-pentenylpalladium derivatives: the 4.5-membered palladacycles [Pd2(μ-Br)2(5-Pf-3-R-1,2,4-η1-η2-pentenyl)2] (Pf = C6F5; R = H (2a), Me (2b)) and the 5.5-membered metallacycles [Pd2(μ-Br)2(5-Pf-3-R-1,2,5-η1-η2-pentenyl)2] (R = H (3a), Me (3b)). Both enyls isomerize to η3-allylic derivatives following two competitive pathways, i.e. (i) Pd migration or (ii) cyclopropane formation and reopening, which lead to the isomeric η3-allylpalladium complexes [Pd2(μ-Br)2(5-Pf-3-R-1-3-η3-pentenyl)2] (R = H (5a), Me (5b)) and [Pd2(μ-Br)2(4-Pf-3-(CH2R)-1-3-η3-butenyl)2] (R = H (6a), Me (6b)), respectively. After the cyclopropane formation-reopening process, [Pd2(μ-Br)2(3-CH2Pf-1,2,5-η1-η2-pentenyl)2] (8) is also formed which isomerizes to 6b. The reaction of a mixture of the η1-η2-pentenyl complexes at low temperature with CO/NaOMe gives methyl ester derivatives. Again, the formation of the major ester CH2=CH(CH2Pf)CHRCOOMe involves cyclopropane formation-reopening in the enyl derivative 2. An unusual acyl complex, [Pd(μ-Br)(η1-η2-3-CH2Pf-1-oxo-4-pentenyl)]2 (15) containing a chelating η2-η1-olefin acyl moiety has been characterized.
