Metallation, ortho

This protective group was used to improve the directed ortho metallation. Cleavage... 

The Henegar modification of the Friedlander reaction has been recently reported. The A-Boc protected derivative of o-aminobenzaldehyde (25, in this case prepared via directed ortho metallation of 24) is a stable, crystalline compound that can be stored for extended periods (in contrast with 4, which typically is freshly prepared). Treatment of 25 with ketone 26 in acetic acid results in deprotection of the aniline in situ and subsequent formation of 27, an intermediate in the synthesis of mappicine. 

When both a-positions are blocked, the highly specific reactivity toward organolithium compounds disappears and metalation depends on the kind of a-substituents present. Thus whereas 2,5-dimethylthio-phene is not metalated at all, 2-methoxy-5-methylthiophene is metalated in the 3-position, similar to the known ortho metalation of anisole. On the other hand, 5-methyl-2-methylthiothiophene is also metalated (in low yield) in the 3-position, in contrast to thioanisole... 

Polysubstituted 3-thiofiirans which are receiving a great interest as flavour and odour chemicals have been obtained by mono-//J5osubstitution and ortho-metallation from 3,4-dibromofuran <96T4065>. Dihydrofuran is used in a new synthesis of ketones from acids via acyl hemiacetals (Scheme 8, <96JOC6071>). 

Concerning the yldiide Ph3P=CH-Li, the question as to whether it could be obtained by direct lithiation of the ylides 23 (Y=H), for a long time in debate between Schlosser and Corey, could have found an answer. Effectively NMR studies seem to show that a directed ortho-metallation occurs on an aromatic ring when 23 is reacted with t-BuLi [65], leading thus to the formation of 24 whose evolution does not afford Ph3P=CH-Li (Scheme 13). 

However an unexpected new cyclic ruthenium phosphorus ylide half-sandwich complex 42 has been obtained by reaction of 41 with dichloromethane as solvent [79]. The cyclisation involves a C-Cl activation and corresponds to the incorporation of the methylene moiety in the P-C bond and to the ortho-metal-lation of one phenyl of the phosphine. An other novel unusual phosphonium ylide ruthenium complex 43 has also recently been described [80]. 

Under comparable conditions, no ortho-metallated species are obtained from the 1-phenyl-pyrazole (1-Phpz) adduct, Au(N)Cl3, formed by reaction of 1-Phpz with Na[AuCl4] [17[. 

Chamoin S, Houldsworth S, Kruse CG, Bakker WI, Snieckus V. The Suzuki-Miyaura cross coupling reactions on solid support. Link to solution phase directed ortho metalation. The Leznoff acetal linker approach to biaryl and heterobiaryl aldehydes. Tetrahedron Lett 1998 39 4179-4182. 

The X-ray structures of two ortho-metalated compounds, (166), have been discussed.310 Weak interactions between the hydride ligand and C—H protons of the PPh3 groups are recorded. 

The coordinatively unsaturated [Ni(PPh3)3] (1034) has trigonal planar Ni,2502 the structure showing some close approach of three o-phenyl H atoms to the central Ni (2.74-3.09 A) with implications for ortho-metallation. 

Complexes with mixed C,P or C,As donor ligands are derived of ortho-metalated phosphines or arsines or of methanide derivatives. The dinuclear complexes [Au2(C6F[3-2-EPh2-6-R)2] (E = P (589), As R = H, Me) are obtained by reaction of 2-EPh2-6-R-C6F[3Li with [AuBr(PEt3)] at —70 °c.2002 2004,20 6 The treatment of the dimer [Au2(C6Fl4PPh2)2] with methyltriflate yields, unexpectedly, [Au5(C6Fl4PPh2)4]+.3134 The mixed dinuclear derivative [Au2(5-Me-C6H3-2-... 

The insertion reactivity of the electrophilic iridium methylene species 57 was noted above. A cationic iridium methylene complex is also the likely intermediate in the thermal rearrangement of Ir(=CH2)I(CO)(PPh3)2 to the ortho-metallated ylide complex 75 ([Pg.167]

Triruthenium Complexes with Ortho-Metallated Ligands... 

Triruthenium Complexes with Ortho-Metallated 2,2 -bipyridine or 1,10-Phenanthroline... 

Fig. 4 ORTEP drawing (30% thermal ellipsoids) of R113 cluster dimer 37a linked by ortho-metallated bpym...

Fig. 7 UV-vis-nIR absorption spectra of 3+ trimer 46 (line), neutral trimer 46a (dots) and 2+ trimer 46b (dashes) containing ortho-metallated pyq, measured in dichloromethane solutions...

An ( )-TolBINAP-Ir complex with a protic amine such as benzylzmine as the additive has been applied for the hydrogenation of 2-phenyl-3,4,5,6-tetrahydropyridine, and enantioselectivity up to 90% ee is obtained.314 An ortho-metallated Ir dihydrid complex has been used in the hydrogenation of 2-methylquinoxaline, and enantiopurity up to 90% ee has been obtained for the 2-methyl-1,2,3,4-tetrahydroquinoxaline product (Scheme 16).327... 

Deactivation may also be inherent to the catalytic system and similar to deactivation of the homogeneous catalyst. An example is the formation of a stable ortho-metalated species. 

K. Dedeian, P.I. Djurovich, F.O. Garces, G. Carlson, and R.J. Watts, A new synthetic route to the preparation of a series of strong photoreducing agents fac tris-ortho-metalated complexes of Iridium (III) with substituted 2-phenylpyridines, Inorg. Chem., 30 1685-1687 (1991). 

Angular anthracyclinonesThe ortho-metalation of a benzyl alcohol has been used to provide a synthesis of angular benzanthraquinone. Thus the cw-tetralol... 

C02 to give adduct complexes. NMR evidence indicates that [ReH(dppe)2] undergoes rapid but reversible ortho metalation and insertion into the C-H bonds of benzene. Irradiation of the complexes [ReH5L3] (L = PMe2Ph, PMePh2, PPh3) and [ReH3 ... 

This species is extremely reactive and does not persist as such but instead undergoes the ortho-metallation reaction shown in... 

Scheme 14. Synthetic scheme for an ortho-metallation resistant hindered 2,6-diphenyl phenol derivative.142...

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