Cobalt-containing heterocycles

Only cobalt- and iridum-containing heterocycles were described between 1995 and 2006. Protonation of the alky-nylcobalt complex Co(C CPh)(CO)[PPh(OEt)2]3 62 by HBp4-Et20 or CE3SO3H allowed the synthesis of [Co 7 7 -C H4P(OEt)2C(H)=C(H)Ph (CO) PPh(OEt)2 2]BPh4 metallacycle 17, which was characterized crystal-lographically and spectroscopically <19950M4126>. 

Scheme l.545 The cobalt and nickel complexes M(S2N2H)2 (M = Co or Ni) may also take part in condensation reactions with chlorosilanes to give cobalt- and nickel-containing heterocyclic systems (Scheme 2).546 The... 

The sulfite group present in the heterocyclic ring of endosulfan is rapidly hydrolyzed by alkali. In the presence of atmospheric oxygen it then oxidizes divalent cobalt to cobalt(III). Phosphamidon, which contains a 2-chloro-2-diethylcarbamoyl group, ox-... 

The preparation of oximes from olefins is a valuable approach for the synthesis of nitrogen-containing compounds such as amino acids and heterocycles. Okamoto and colleagues have reported that a catalytic reduction-nitrosation of styrenes 31 with ethyl nitrite and tetrahydroborate anion by the use of bis(dimethylglyoximato)cobalt(II) complex afford the corresponding acetophenone oximes 32 (Scheme 23). 

Table 23 Preparations Cobalt Complexes Containing Six-Membered N-Heterocyclic Ligands... 

In chapter 6 we described the use of the remarkable Pauson-Khand reaction for the synthesis of cyclopentenones. If the components (CO, alkene and alkyne) are tethered by a nitrogen atom, a heterocycle will also be formed. The first stage in this process is to couple the cobalt carbonyl complex, e.g. 236, of ahalo-alkyne with an amine containing the alkene in the side chain. The best way to do this is to react 234 with Co2(CO)9 to give 235 and then 236 and to capture this complex with the amine without isolation of intermediates.34... 

The skeleton of vitamin 8,2 (i.e., the porphyrin nucleus minus C-20) is called corrin. The compound containing the corrin nucleus is edled a corrinoid. The compound containing the cobalt atom and the standard side chains in the free acid form is called cobyrinic acid, but cobyric acid when the side chains are at positions a, b, c, d, e, g, are in the amide form. Cobyrinic acid substituted with D-l-amino-2-propanol at position f is called cobinic acid. The substituted cobyric acid is called cobinamide. Cobinic acid substituted with d ribofuranose-3-phosphate at position 2 of the aminopropanol is called cobamic acid the substituted cobinamide is called cobamide. Many 8,2 vitamins and derivatives in which the heterocyclic base is 5,6-dimethylbenzimidazole are given the trivial name cobalamin see D. Dolphin, ed., 8,2, Wiley-Interscience, New York, 1982. 

Bromoacetals containing carbon-carbon triple bonds were cyclized to 5-membered heterocyclic rings (5- xo-exclusively) using [chloropyridine-bis(dimethylglioximato)] cobalt(I) (cobaloxime I) generated from cobaloxime III as an electron transfer reagent (mediator) in alkaline methanol solution at constant current. The most efficient molar substrate/mediator ratio was 2 1 with 70-87% yields of isolated products. The proposed... 

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