Cobalt halides synthesis

Typically, the synthesis of the precursor iron(II) and cobalt(II) halide complexes proceeds by treatment of an anhydrous or hydrated divalent iron or cobalt halide (e.g. MX2 jcH20 or MX2 X = Cl or Br) with 1 (and also 2-4) in... 

This led us to find new catalytic systems able to turn the electrochemical process to the synthesis of organozinc compounds. In this context, a simple cobalt halides salt can be used advantageously6. As a matter of fact, the work devoted to the study of the... 

A more efficient and more generahy applicable cobalt-catalysed Mizoroki-Heck-type reaction with aliphatic halides was elegantly developed by Oshima and coworkers. A catalytic system comprising C0CI2 (62), l,6-bis(diphenylphosphino)hexane (dpph 73)) and Mc3 SiCH2MgCl (74) allowed for intermolecular subshtution reactions of alkenes with primary, secondary and tertiary alkyl hahdes (Scheme 10.25) [51, 53]. The protocol was subsequently applied to a cobalt-catalysed synthesis of homocinnamyl alcohols starting from epoxides and styrene (2) [54]. 

A. I. Yashin, E. I. Tinyakova, Yu. V. Bryantseva, K. G. Miesserov, V. Mahdi, and B. A. Dolgoplosk. Synthesis of oligomeric Tr-allyl complexes based on reactions of tri-isobutyl-alurainium with nickel and cobalt halides. Izvest. Akad. Nauk S.S.S.R., Ser. khim., 1978, 27, 1608. 

Low-valent cobalt pyridine complexes, electrogenerated from CoCl2 in DMF containing pyridine and associated with a sacrificial zinc anode, are also able to activate aryl halides to form arylzinc halides.223 This electrocatalytic system has also been applied to the addition of aryl bromides containing an electron-withdrawing group onto activated alkenes224 and to the synthesis of 4-phenylquinoline derivatives from phenyl halides and 4-chloroquinoline.225 Since the use of iron as anode appeared necessary, the role of iron ions in the catalytic system remains to be elucidated. 

Synthesis of 2,6-Bis(imino)pyridine Iron(II) and Cobalt(II) Halides. 110... 

Scheme 2 Synthesis of bis(arylimino)pyridine iron(II) and cobalt(II) halides...

The synthesis of metalloporphyrins which contain a metal-carbon a-bond can be accomplished by a number of different methods(l,2). One common synthetic method involves reaction of a Grignardreagent or alkyl(aryl) lithium with (P)MX or (PMX)2 where P is the dianion of a porphyrin macrocycle and X is a halide or pseudohalide. Another common synthetic technique involves reaction of a chemically or electrochemically generated low valent metalloporphyrin with an alkyl or aryl halide. This latter technique is similar to methods described in this paper for electrosynthesis of cobalt and rhodium a-bonded complexes. However, the prevailing mechanisms and the chemical reactions... 

Fischer polypeptide synthesis org chem A synthesis of peptides in which a-amino acids or those peptides with a free amino group react with acid halides of a-haloacids, followed by amination with ammonia. fish-ar pal-e pep,tTd. sin tha sas ) Fischer projection orgchem) A method for representing the spatial arrangement of groups around chiral carbon atoms the four bonds to the chiral carbon are represented by a cross, with the assumption that the horizontal bonds project toward the viewer and the vertical bonds away from the viewer fish-ar pra.jek-shon) Fischer s salt See cobalt potassium nitrite. fish-3rz solt)... 

Lee, K. Y. Kawthekar, R. B. Kim, G. J. (2007) Synthesis of chiral intermediates eatalyzed by new ehiral polymeric (salen) cobalt complexes bearing Lewis acidic metal halides., Korean Chem. Soc., 28 1553-1561. 

Other interesting anionic transition metal amido derivatives have come from the reactions of primary amido ligands with metal halides by Fenske and coworkers. This has allowed the synthesis of a range of cobalt, nickel and copper amido cluster species with unusual structures which also incorporate NPh as coligand (cf. Table... 

A Belgian patent (178) claims improved ethanol selectivity of over 62%, starting with methanol and synthesis gas and using a cobalt catalyst with a halide promoter and a tertiary phosphine. At 195°C, and initial carbon monoxide pressure of 7.1 MPa (70 atm) and hydrogen pressure of 7.1 MPa, methanol conversions of 30% were indicated, but the selectivity for acetic acid and methyl acetate, useful by-products from this reaction, was only 7%. Ruthenium and osmium catalysts (179,180) have also been employed for this reaction. The addition of a bicyclic trialkyl phosphine is claimed to increase methanol conversion from 24% to 89% (181). 

An unusual synthesis of acyldienes from conjugated dienes, carbon monoxide, and alkyl or acyl halides using cobalt carbonylate anion as a catalyst should be mentioned here (57). The reaction apparently involves the addition of an acylcobalt carbonyl to a conjugated diene to produce a l-acylmethyl-7r-allylcobalt tricarbonyl, followed by elimination of cobalt hydrocarbonyl in the presence of base. The reaction can thus be made catalytic. Since the reaction was discussed in detail in the recent review by Heck (59), it will not be pursued further here. 

Among the electrochemical syntheses related to the change of metal oxidation number, we emphasize obtaining acetylacetonates of divalent iron, cobalt, and nickel [551,623]. The method of alternating-current electrochemical synthesis was applied to isolate Ji-complexes of monovalent copper with allylamines, allylimines, and ally-lurea from the salts of divalent copper [624-628], We note that the same method was used for preparation of analogous ji-complexes with copper(II) halides (X = Cl, Br) [629a]. Other electrochemical syntheses with participation of metal salts and complexes are described in monographs [201,202] and literature cited therein. 

The Takai-Utimoto reaction of alkyl halides 360 with aldehydes 361 is a convenient method for the synthesis of branched alcohols 363 with high functional group tolerance [455]. Vitamin B12 362 or cobalt phthalocyanine served as the catalyst and CrCl2 as the stoichiometric reducing agent (Fig. 99). The reactions proceeded well with aromatic and aliphatic aldehydes. 

By using this method, 4-methyl-2 -cyanobiphenyl, an important intermediate for the synthesis of the antihypertensive drug Losartan, can be easily prepared.132 2-(t>-Chlorophenyl)-oxazoline reacts with excess of arylmagnesium halide without catalysis, as it was shown by Meyers for 2-(o-methoxyphenyl)-oxazolines.133 Cobalt(ll) salts catalyze the coupling of Grignard reagents with a-chloroazines at —40°C in ether (Scheme 47).134 135... 

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