737003-75-7Relevant academic research and scientific papers
Aminomethyl and aminoacetyl complexes of palladium(II), platinum(II), iron(II) and rhenium(I) with N-phthaloyl as amino protecting group and mechanistic studies on the palladium-catalyzed amidocarbonylation
Enzmann, Armin,Eckert, Markus,Ponikwar, Walter,Polborn, Kurt,Schneiderbauer, Stefan,Beller, Matthias,Beck, Wolfgang
, p. 1330 - 1340 (2007/10/03)
New aminomethyl and aminoacetyl complexes with N-phthaloyl as the amino protecting group were synthesised by oxidative addition of N-phthaloylmethyl or -acetyl halide to carbonylmetallates or to Pd(PPh3)4 or [Pt(C2H4)(PPh3)2] to give [Re{C(O)CH2N-phthaloyl}(CO)5] (1), [FeCp(CH 2N-phthaloyl)(CO)2] (2), [FeCp{C(O)CH2N- phthaloyl}(CO)2] (3), trans-[PdBr(CH2N-phthaloyl)(PPh 3)2] (4) and trans-[Pd{C(O)CH2N-phthaloyl}(X) (PPh3)2] (X = Br, Cl; 5, 6). The bis(phosphane) complexes [Pd(CH2N-phthaloyl)(X)-(R2PCH2CH 2PR2)] and [Pd{C(O)CH2N-phthaloyl}(X)-(R 2PCH2CH2PR2)] (X = Cl, Br; R = Ph, C6H11) 8-13 were obtained by ligand exchange from 4, 5 or 6 with the corresponding bis(phosphanes). Halide abstraction from 4, 5, 6, 10, 11 or 12 gives the cationic complexes 14 and 15 with formation of a five-membered chelate ring which includes one carbonyl atom of the phthaloyl group. The reaction of 6 with the tridentate ligand PhP(CH2CH 2PPh2)2 affords the five-coordinate complex 16 and from [Pt(C2H4)(PPh3)2] and organic halides the platinum(II) complexes trans-[Pt(CH2N-phthaloyl) (Cl)(PPh3)2] (17) and [PtC(O)CH(CH2Ph)N- phthaloyl(Cl)(PPh3)2] (18) were isolated. The structures of 2, 11, 14, 15 and 16 were determined by single-crystal X-ray analysis. The mechanism of the palladium-catalysed amidocarbonylation was studied using phthalimide, formaldehyde and CO as a model system which gives N-phthaloylglycine in good yield. The proposed elementary steps in the palladium-catalysed amidocarbonylation could be verified by use of the possible intermediates phthaloyl-NCH2OH and phthaloyl-NCH2Br as substrates, by oxidative addition of phthaloylmethyl bromide to Pd0, by insertion of CO into the palladium-carbon-bond of 4 and 8 with formation of 5 or 9, respectively, and by use of the isolated possible intermediates 4, 5 and 14 as catalysts. Thus, all crucial steps of the palladium-catalysed amidocarbonylation with the model system phthalimide/formaldehyde/CO have been verified for the first time. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
