Indium-carbon bonds

Regio- and Stereoselectivity. For the allylation of carbonyl compounds mediated by indium and other compounds in aqueous media, usually the carbon-carbon bond forms at the more substituted carbon of the allyl halide, irrespective of the position of halogen in the starting material. However, the carbon-carbon bond forms at the less-substituted carbon when the y-substituents of allyl halides are large enough (e.g., trimethylsilyl or tert-butyl) as shown by Chan et al.139 (Scheme 8.10). The following conclusions can be drawn ... 

The thallium complexes show somewhat different electrochemical behavior, and reversible oxidations are observed for both n-alkyl and n-aryl thallium porphyrins, indicating that the oxidized complexes have a more stable metal—carbon bond than the gallium or indium analogs. Spectroelectrochemistry revealed that the first oxidation is porphyrin ring-centered. The first reduction is reversible and ring... 

Most of the studies on organo-gallium, indium, and thallium porphyrin complexes have focused on synthesis and properties of the complexes, and rather little attention has been devoted to reaction chemistry. Two areas which have received some attention are the insertion of small molecules (SO2 or CO2) into the metal—carbon bonds and photochemical metal—carbon bond cleavage. The... 

Inter-ring metal migrations, dynamic NMR studies, 1, 412 Intracyclic germanium-carbon bond formation large rings, 3, 706 small rings, 3, 703 Intramolecular Alder-ene reactions with metals, 10, 576 with palladium, 10, 568 with rhodium, 10, 575 with ruthenium, 10, 572 with transition metal catalysts, 10, 568 Intramolecular allylations, in cyclizations, with indium compounds, 9, 679... 

The zinc-mediated Reformatsky reaction is one of the classical methods for carbon-carbon bond formation. To date, various main group metals and transition metals have been used for this reaction. Rieke s activated indium powder mediates readily the coupling of ethyl a-bromoacetate and a variety of carbonyl compounds yielding /3-hydroxy esters in good yields (Scheme 87).3 Later, commercially available indium powder has been found to be equally effective for the indium-based Reformatsky reaction in THF.28 This indium Reformatsky reaction is accelerated by ultrasound irradiation (Scheme 88).322,323 Indium(i) iodide also mediates the Reformatsky reaction of aldehydes and ketones to give /3-hydroxy esters, presumably via organoindium(m) diiodide (Scheme 89).27... 

Nair, V., Ros, S., Jayan, C. N., Pillai, B. S. Indium- and gallium-mediated carbon-carbon bond-forming reactions in organic synthesis. Tetrahedron 2004, 60,1959-1982. 

A wide variety of carbon-carbon bonds can be formed in aqueous conditions (Figure 4.15). An indium-mediated Barbier reaction on unprotected galactose led... 

Intermolecular alkyl radical addition to imine derivatives was studied in aqueous media using indium as a single electron transfer radical initiator. The one-pot reaction based on radical addition to glyoxylic hydrazone provided a convenient method for preparing the a-amino acids. Indium-mediated radical addition to an electron-deficient C=C bond also proceeded effectively to provide a new carbon-carbon bond-forming method in aqueous media (Scheme 7.11).15... 

Another strategy involving tandem radical reactions that offers an advantage of multiple carbon-carbon bond formation in a single operation in the aqueous medium tandem construction of carbon-carbon bonds has been widely being studied by Naito and co-workers (Scheme 7.12). The indium-mediated tandem... 

The indium-mediated Barbier reaction has certainly become one of the most popular reactions for creating a carbon-carbon bond under aqueous conditions and has led to spectacular developments in recent years. Compared to other metals, indium is resistant to oxidation, hydrolysis, and has a very low first ionization potential (5.79 eV, in contrast to the second one which is quite normal) which confers on it a remarkable reactivity in Barbier-type reactions. In 1991, Li and co-workers reported the first allylation of aldehydes and ketones mediated by indium in water without any additives or special activation [133]. In particular, the use of indium allowed reactions with acid-sensitive compounds [134] or the preparation of complex carbohydrates such as deaminated... 

Similar photochemical insertion reactions are observed for indium alkylporphy-rins In the presence of pyridine and under irradiation by visible light, carbon dioxide inserts into the carbon-indium o bond leading to stable carboxylate indium porphyrins (Scheme 10). 

The presence of pyridine and irradiation by visible light are required for the insertion of carbon dioxide into the indium-carbon o bond. However, the UV-visible spectrum of the starting complex is invariant with increasing amounts of pyridine, thus implying a five coordinate species in the media studied. These results contrast with those obtained for... 

The interplanar separation of Rh(OEP)In(OEP) is 3.41 A compared to 3.26 A for [Ru(OEP)]2 As is also observed for the ruthenium dimer the In(OEP) core is twisted 21.8° relative to the Rh(OEP) group. Both the indium and rhodium atoms have an out-of-plane distance A4N which is the same as that previously reported for the corresponding o-bonded metal carbon complexes (given in Table 15 of part B V). A covalent radius of 1.36 A may be estimated from the metal-carbon bond length in In(TPP)(CH3). Similarly the covalent radius of the rhodium atom in Rh(OEP)(CH3) is equal to 1.26 A, giving a predicted covalent Rh-In distance of 2.62 A. This latter value is in good agreement with the observed value (2.584(2) A). In addition, the reactivity of the dimer... 

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