|
|
Bibliographic Information
Air stable, sterically hindered ferrocenyl dialkylphosphines for palladium-catalyzed C-C, C-N, and C-O bond-forming cross-couplings. Kataoka, Noriyasu; Shelby, Quinetta; Stambuli, James P.; Hartwig, John F. Dep. Chem., Yale Univ., New Haven, CT, USA. Journal of Organic Chemistry (2002), 67(16), 5553-5566. Publisher: American Chemical Society, CODEN: JOCEAH ISSN: 0022-3263. Journal written in English. CAN 137:217039 AN 2002:509541 CAPLUS
Abstract
Pentaphenylferrocenyl di-tert-butylphosphine I (R = R1 = Ph) was prepd.; the scope of various cross-coupling processes catalyzed by palladium complexes of I has been investigated. I (R = R1 = Ph) was prepd. by lithiation of ferrocene followed by removal of solvent, addn. of a 5:1 pentane:THF mixt., and addn. of di(tert-butyl)chlorophosphine to give mono(di-tert-butylphosphino)ferrocene with high chemoselectivity; arylation of the ferrocenylphosphine with chlorobenzene as a solvent in the presence of palladium (II) acetate and sodium tert-butoxide yielded I in 40-65% yield overall. I (R = R1 = Ph) acts as a highly effective ligand for palladium-catalyzed amination and for Suzuki coupling reactions with aryl- and alkylboronic acids. Unactivated, electron-rich, and electron-poor aryl bromides and chlorides undergo coupling reactions in the presence of palladium complexes of I (R = R1 = Ph) with high turnover nos. Aryl bromides were coupled to alcs. in the presence of I (R = R1 = Ph); silanols and electron-rich phenols were coupled to activated aryl halides in the presence of I (R = R1 = Ph). Intramol. coupling reactions of alcs. and aryl bromides were successful, although substrates with hydrogens a to the alc. oxygen underwent some b-hydride elimination. Acyclic and cyclic primary and secondary alkyl- and arylamines underwent coupling reactions with aryl bromides and chlorides in the presence of I (R = R1 = Ph). Aryl- and primary alkylboronic acids underwent coupling reactions in the presence of I (R = R1 = Ph); coupling of alkylboronic acids with aryl halides was successful in the absence of toxic or expensive bases. Other substituted ferrocenylphosphines I (R = R1 = 4-MeOC6H4, 4-F3CC6H4) were prepd. but palladium catalysts derived from the ligands showed little difference in catalytic activity when compared to palladium catalysts derived from I (R = R1 = Ph). Palladium catalysts derived from I (R = R1 = 3,5-Me2C6H3) were active in coupling reactions with aryl halides and alcs.
but not in amination or Suzuki coupling reactions; I (R = Ph; R1 = H) acted as a catalyst for coupling reactions but gave significantly decreased yields due to decreased steric hindrance of the reaction center in the palladium complexes. I (R = R1 = Ph) not only generates highly active palladium catalysts, but is also air stable both in soln. and in the solid state. Palladium(0) complexes of I (R = R1 = Ph) are air stable solids and react only slowly with oxygen in soln. The crystal structures of I(R = R1 = Ph; R = Ph, R1 = H) were detd. by x-ray crystallog.
_ |
|
回复此楼