Proazaphosphatrane ligands

Proazaphosphatrane ligands in combination with Pd2(dba)3 also generate highly active catalysts for Buchwald-Hartwig amination of aryl chlorides, e.g. (132) from (130) and (131). The PAP ligand with R = Bu was particularly effective and the catalyst performed extremely well with sterically hindered substrates. ... 

Proazaphosphatrane ligands, such as 420, partnered with palladium species generated highly active catalysts for Buchwald-Hartwig reactions. An example of such transformations was illustrated when 26 was able to react with 413 to afford 414 [149]. 

Scheme 5.47 Stille coupling using proazaphosphatrane ligand...

In 2004 Verkade and co-workers reported a catalyst system of general applicability for the Stille coupling of aryl chlorides at 110 °C in dioxane and the coupling of aryl bromides at room temperature in THF. The catalyst system uses Pd2(dba)3, the bulky proazaphosphatrane ligand 32 in presence of CsF (or Me4NF). 

Head-to-tail dimerisation of methyl acrylate to the dimethyl ester of 2-methylenepentane-dioic acid (126) occurred in 82-85% yield in the presence of catalytic amounts of P(RNCH2CH2)3N with R = PP, Bu or Bz but the less sterically hindered proazaphosphatrane with R = Me, gave oligomer or pol-ymer. The proazaphosphatrane, P(RNCH2CH2)3N with R = Bu also acts as an effective ligand for the palladium-catalyzed direct arylation of ethyl cyano-acetate (127) with aryl bromides (e.g. 128) to form (129) in high yield. ... 

A new catalyst system for the synthesis of a-aryl substituted nitriles has been reported. The Bu-proazaphosphatrane serves as an efficient and versatile ligand for the palladium... 

The proazaphosphatrane bases serve as an effective ligand for the palladium catalysed amination of a wide array of bromides and iodides. Other bicyclic or acyclic triaminopho-sphines, even those of similar basicity and/or bulk, were inferior. The palladium catalysed... 

P(o-tolyl)3, P( Bu)3, Ph5FcP(PBu)2 (Q-phos), heterocyclic carbenes, (BiaryllPRg. -OP(f-Bu)2, and Verkade s proazaphosphatranes L = Chelating bidentate ligands dppf, BINAP, Xantphos, and Josiphos ligands... 

Scheme 6.13 Room-temperature Stille coupling employing a proazaphosphatrane as a ligand [31 b,cj.

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