Cobalt bromide-triphenylphosphine

Reactive halogen on carbohydrates was readily replaced by cobalt tetracarbonyl anion in ether solution. As an example, treatment of tetra-O-acetyl-a-D-glucopyranosyl bromide (80) with sodium cobalt tetracarbonyl in ether under 15 atmospheres of anhydrous carbon monoxide for 2 days at room temperature, followed by addition of triphenylphosphine, gave an almost quantitative yield of 2,3,4,6-tetra-0-acetyl-/8-D-glucosyl cobalt tricarbonyl triphenylphosphine... 

Cobalt(II) bromide-triphenylphosphine, catalyst, 53,30,32 Condensation, of p-acetylbenzenedi-azonium bromide with acrylic acid, 51,1... 

As mentioned in the chapter on the reaction mechanism, the anion, especially of Ni-salts, is important in affecting the reaction course. The catalytic efficiency of the nickel halides strongly increases in the series fluoride, chloride, bromide, iodide [374—376]. The molar ratio of cobalt or nickel to iodine is also very important [414]. As in the hydroformylation reaction, metal carbonyls substituted by phosphine ligands are very reactive [377, 1009], and especially modified rhodium and palladium catalysts [1021, 1045] allow reactions under mild conditions. Thus, the nickel bromide triphenylphosphine allyl bromide complex shows an increased reactivity in the carbonylation of acetylenes. On the other hand, carbonyls substituted by phosphine ligands are also readily soluble in the reaction mixture [345, 377]. 

Bis(glyoximato)cobalt(II) complexes of the types Co(DH)2B2 and Co(DH)2B2 (DH = disubstituted glyoxime, B = base, e.g. pyridine or triphenylphosphine) reduce benzyl bromide in benzene and acetone solutions ... 

The octacyclic dimer (+)-94 could be obtained in short order from the tetracyclic bromide (+)-93 via a Co(I)-mediated reductive dimerization protocol first implemented in our prior syntheses of (+)-chimonanthine (7), (+)-folicanthine (8), and (—)-calycanthine (9) [7]. Simple exposure of intermediate (+)-93 to tris (triphenylphosphine)cobalt(I) chloride [48] in acetone under anaerobic conditions rapidly afforded dimer (+)-94 in 46 % yield. While higher yields (52 % yield) could be obtained in tetrahydrofuran on small scale, performing the reaction in acetone reproducibly afforded higher yields on gram scales. Notably, the product was obtained in similar efficiency on multi-gram scale (43 % yield on 8-g scale)... 

TRIMETHYLPENTANAL, 51, 4 TRIMETHYLSILYL AZIDE, 50, 107 Triphenylphosphine-cobalt(II) bromide, catalyst, 53, 30,... 

Again, cobalt hydrotricarbonyl probably adds initially. The addition could be either a 1,4-addition or a 1,2-addition in which cobalt initially adds to the second carbon atom of the diene, and then undergoes an allylic rearrangement. The 3-pentenoylcobalt tricarbonyl triphenylphosphine prepared in this manner contains considerably more of the cis isomer than the same compound prepared from trans crotyl bromide and sodium cobalt tetracarbonyl. This, indicates that the hydrocarbonyl prefers cis addition (47). 

Nitrosylpentaamminecobalt(II) chloride, synthesis 49 cts-Bromoamminebis (ethylenediamine) cobal t (111) bromide, CIS- and trans-aquoamminebis(ethylenediamine)cobalt(IIl) bromide, and cis- and triphenylphosphine)rhodium and chloro-carbonylbis(triphenylarsine)rhodium, synthesis 56 Sodium hexachlororhodate(III) 2-hydrate and potassium hexachlororhodate(III) 1-hydrate, synthesis 57 Ammonium hexachloroiridate(IV), synthesis 58 Resolution of the tris(l,10-phenanthroline)nickel(II) ion, synthesis 59... 

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