Potassium hexacyanoferrate , reagent

The actual catalyst is a complex formed from osmium tetroxide and a chiral ligand, e.g. dihydroquinine (DHQ) 9, dihydroquinidine (DHQD), Zj -dihydroqui-nine-phthalazine 10 or the respective dihydroquinidine derivative. The expensive and toxic osmium tetroxide is employed in small amounts only, together with a less expensive co-oxidant, e.g. potassium hexacyanoferrate(lll), which is used in stoichiometric quantities. The chiral ligand is also required in small amounts only. For the bench chemist, the procedure for the asymmetric fihydroxylation has been simplified with commercially available mixtures of reagents, e.g. AD-mix-a or AD-mix-/3, ° containing the appropriate cinchona alkaloid derivative ... 

When oxidized by iron(III) ions 4-aminoantipyrine reacts with phenols to yield colored quinonoid derivatives (cf. 4-aminoantipyrine — potassium hexacyanoferrate(III) reagent in Volume 1 a). It is an oxidative coupling based on the Emerson reaction. 

Some luminol derivatives have been developed as CL labeling reagents. Analytes prelabeled with luminol derivatives are separated by HPLC, mixed with postcolumn reagents such as hydrogen peroxide and an alkaline solution of potassium hexacyanoferrate (III), and then detected by a CL detector. Highly sensitive determination is possible by optimizing the conditions to increase the CL reaction efficiency for each analyte. 

Using a different dimerization method, namely phenolic oxidation, chiral substrates react in a more stereoselective manner than under reductive conditions. The choice of oxidizing reagent may drastically affect the stereochemical outcome of the reaction. Thus, when potassium hexacyanoferrate(III) is used (17 )-l,2,3,4-tetrahydro-6-methoxy-l,2-dimethyl-7-isoquino-linol couples to give a mixture of atropisomers 3 in 38 % yield and with a d.r. (M)I(P) of 45 553,4. Only one single atropisomer, namely (A/)-3, is formed, in a 66% yield by anodic oxidation, which is attributed to electrode surface effects3. 

Potassium hexacyanoferrate(II) solution white precipitate of variable composition if the reagent is added in some excess the composition of the precipitate is K2Zn3[Fe(CN)6]2 ... 

The spot-test technique is as follows. In adjacent depressions of a spot plate place a drop of distilled water and a drop of the test solution. Add a drop of the reagent (equal volumes of 0-5m iron(III) chloride solution and 0 033m potassium hexacyanoferrate(III) solution) to each. A blue colouration or precipitate is formed. 

Mild oxidation of 3-substituted quinoxalin-2-ones, formed by reaction of quinoxalin-2(l//)-ones and Grignard reagents, with potassium hexacyanoferrate(III) or hydrogen peroxide gives aromatic systems. ... 

Potassium ferricyanide [potassium hexacyanoferrate(lll)], K3Fe-(CN), in the presence of a base, dehydrogenates hydroaromatic compounds to aromatic compounds [919] and can cause dehydrogenative cy-clizations [920]. The reagent is used for the conversion of acid hydrazides into aldehydes [921], of sterically hindered phenols into phenoxy radicals [922, 923], and of primary amines into nitriles [924], Tertiary amines are demethylated to secondary amines [925, 926]. 

---