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

Abstract

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(CH2N‐phthaloyl)(CO)2] (2), [FeCp{C(O)CH2N‐phthaloyl}(CO)2] (3), trans‐[PdBr(CH2N‐phthaloyl)(PPh3)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)(R2PCH2CH2PR2)] and [Pd{C(O)CH2N‐phthaloyl}(X)(R2PCH2CH2PR2)] (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(CH2CH2PPh2)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)

Recent chemistry of the η5-cyclopentadienyl dicarbonyl iron anion

“…A rather unusual phthalimidomethyl Fp complex was reported by Enzmann et al [96] after they reacted the Fp anion with bromomethylphthalimide (Scheme 30). This complex was prepared as part of a study to understand N-protected groups and Scheme 29. their role and use as catalysts in amidocarbonylation reactions for potential use in peptide synthesis.…”

“…Phthaloyl chloride was also reacted with Fp anion using a known procedure. Although Beck and coworkers also prepared [96] an Fp phthaloylacetyl complex from Fp anion and phthaloylacetyl chloride (Scheme 66). The N-protected aminoacetyl Fp complex could be useful for the synthesis of peptides.…”

Catalysts for Cross‐Coupling Reactions with Non‐activated Alkyl Halides

“…[63] Model studies with N-(chloromethyl)phthalimides revealed the palladium-catalyzed activation of an intermediate a-halo N-acyl amine. [64] Subsequent carbonylation of the resulting alkyl palladium species leads directly to a wide range of amino acids, such as aryl glycines and hydantoins. [65] …”

The Role of Anions in Addressing the Outcome of the Reaction of Tetramethylthiourea with cis‐PtII(phos)2 Moieties (phos = PPh3 or ${1 \over 2}$dppe), Cyclometallation vs. Hydrolysis to Monothiocarbamato, and the Crystal Structure of trans‐Bis(N‐dimethylmonothiocarbamato)bis(triphenylphosphane)platinum(II)

“…Note the rather high Pt-P coupling constant, which in trans-Pt II (PPh 3 ) 2 complexes is usually in the 2500-3000 Hz range; higher values have, however, also been reported. [12,15] The FAB + mass spectrum of 9 (see Experimental section) shows only a weak peak (ca. …”