Fremy s salt

Juglone is most readily synthesized by Bemthsen s method. However, this method is too drastic and results in low yields (56). Somewhat better yields are obtained by using Fremy s salt (potassium nitroso disulfonate) as the oxidant (57). By using thallium trinitrate to oxidize 1,5-dihydroxynaphthalene, yields as high as 70% of juglone have been reported (58). 

Oxidation of phenols or anilines to quinones by means of potassium nitrosodlsuHanate (Fremy s salt). 

EPR studies of S-N radicals were reviewed in 1990. Many radicals containing the S-N linkage are persistent for more than several hours in solution at room temperature. Perhaps the best known example is the nitrosodisulfonate dianion [0N(S03)] , named as Fremy s salt. In the solid state this radical dianion dimerizes through weak N 0 interactions, but it forms a paramagnetic blue-violet monomer in solution. Although most chalcogen-nitrogen radicals dimerize in the solid state, a few heterocyclic C-S-N systems can be isolated as monomers (Section 11.3). 

Figure 15.52 Structures of various S-N oxoanions (a) hydroxylamine-A-sulfonate, (b) A-nitrosohydroxylamine A-sulfonate and (c) the dimeric anion in Fremy s salt K2[0N(S03)2])2.

Hydroxylamine trisulfonates, e.g. (K03S)0N-(S03K)2 are made by the reaction of K2SO3 with potassium nitrosodisulfonate (Fremy s salt). Acidification of the product results in rapid hydrolysis to the 0,A-disulfonate which can be isolated as the exclusive product ... 

Quinones are an interesting and valuable class of compounds because of their oxidation-reduction, or redox, properties. They can be easily reduced to hydroquinones (g-dihydroxybenzenes) by reagents such as NaBH4 and SnCl2/ and hydroquinones can be easily reoxidized back to quinones by Fremy s salt. 

Fremy s salt, 631 Frequency (/ ), 419-420 Friedel, Charles, 555 Friedel-Crafts acylation reaction. 557-558... 

Oxidation of 5//-dibenz[7>,/]azepine (12) with Fremy s salt [ON(S03K)2] yields a mixture of acridine-9-carbaldehyde (13) and 2//-dibenz[A,/]azepin-2-one (14).215 The dibenzazepin-2-one 14 is also obtained in 46% yield with bis(trifluoroacetoxy)pentafluoroiodobenzene [PhI(OCOCF3)2] in acetonitrile as the oxidant.221... 

Examples of radicals which are reported to meet these criteria are diphenylpicrylhydrazyl [DPPH, (22)], Koelsch radical (26), nitroxides [e.g. TEMPO (23), Fremy s Salt (24)], triphenylmethyl (25), galvinoxyl (27), and verdazyl radicals [e.g. triphenylverdazyl (28)]. These reagents have seen practical application in a number of contexts. They have been widely utilized in the determination of initiator efficiency (Section 3.3.1.1.3) and in mechanistic investigations (Section 3.5.2). 

Methoxy-5-quinoxalinamine (117, R = H) gave 6-methoxy-5,8-quinoxaline-quinone (118, R = H) [substrate hydrochloride, NaH2P04, H2O, 0N(S03K)2 (Fremy s salt) slowly, 20°C, 12 h 65%] ° 6-methoxy-3-morpholino-5-quinoxalinamine [117, R = N(CH2CH2)20] likewise gave 6-methoxy-3-morpholine-5,8-quinoxalinequinone [118, R = N(CH2CH2)20] (36%)/ ... 

DPPH- has an intense absorption maximum around 520 run (Yordanov and Christova, 1997), and antioxidant capacity and activity measured by the reduction of DPPH- are easily quantified by VIS-spectroscopy (Brand-Williams et al, 1995 Bondet et al, 1997, Espin et al, 2000). The stable radicals Fremy s salt (potassium nitrosodisulphonate) and galvinoxyl (2,6-di-tert-butyl-a-(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-l-ylidene)-p-tolyloxy radical) have been used in a similar manner but with ESR detection, which can be used with samples that are not optically transparent (Gardner et al, 1998). 

The phenanthrene 1,2- and 3,4-diones are synthetically accessible from the related 8 phenols. Oxidation of 2-phenanthrol with either Fremy s salt ((KS0 )2N0) or phenylseleninic anhydride gave phenanthrene 1,2-dione directly (55). Unexpectedly, oxidation of 3-phenanthrol with (KSOg NO yielded 2,2-dihydroxybenz(e)indan-l,3-d-ione (Figure 10). However, phenanthrene 3,4-dione was readily obtained from 3-phenanthrol by Fieser s method entailing diazonium coupling, reduction, and oxidation of the resulting 4-amino-3-phen-anthrol with chromic acid (56). 

An alternative new synthetic approach to chrysene 1,2-dihydro-diol based on Method IV has recently been developed (60). This method (Figure 12) entails synthesis of 2-chrysenol via alkylation of 1-1ithio-2,5-dimethoxy-1,4-cyclohexadiene with 2-(1-naphthyl) e-thyl bromide followed by mild acid treatment to ge nerate the diketone 12. Acid-catalyzed cyclization of 12 gave the unsaturated tetracyclic ketone 13 which was transformed to 2-chrysenol via dehydrogenation of its enol acetate with o-chloranil followed by hydrolysis. Oxidation of 2-chrysenol with Fremy s salt gave chrysene... 

The 3,4-dihydrodiol was also synthesized via Method IV (74). Oxidation of 3-hydroxy-MBA with Fremy s salt gave the 3,4-quinone which underwent reduction with LiAlH to give 19a. The yield in the reduction step was only 15%, but it is likely that this could be substantially improved by the use of the NaBH /02 system (18) developed after these studies were completed. 

The 9,10-dihydrodiol of 3-MC (24a) was synthesized from 9-hy-droxy-3-MC by Method IV (86). Oxidation of this phenol with Fremy s salt in the presence of Adogen 464, a quaternary ammonium phase transfer catalyst, furnished 3-MC 9,10-dione. Reduction of the qui-none with NaBH -C gave pure 24a in good yield. Treatment of 24a with m-chloroperbenzoic acid was monitored by HPLC in order to optimize the yield of the anti diol epoxide (25 ) and minimize its decomposition. 

The 7,8-dihydrodiol of 5-MC (30b) was prepared from 8-hydroxy-5-MC by Method IV (60,103). It was necessary to utilize the 8-rather than the Ot-phenol (i.e. 8-HO-5-MC rather than 7-HO-5-MC), since oxidation of the latter with Fremy s salt was anticipated to take place predominantly in the para position. The 8-hydroxy-5-MC was prepared in our laboratories by a modification of the procedure in Figure 18. An alternative preparation of 8-hydroxy-5-MC via photocyclization of methyl 3-phenyl-2-(l-(6-methoxynaphthyl) propenoate has also recently been described (103). 

Formyl fluoride, 50, 2 Fremy s salt, 52, 86, 88 Furan, 3-aeety1-2,4-dimethyl-, 53, 1... 

OXIDATION WITH THE NITROSODISULFONATE RADICAL. II. USE OF DIPOTASSIUM NITROSODISULFONATE (FREMY S SALT) 4,5-DIMETHYL-1,2-BENZ0QUIN0NE, 52, 88... 

Fremy s salt, which is frequently employed in a wide range of oxidation reactions [l], has been shown to selectively oxidize benzylic alcohols in preference to saturated and allylic alcohols [2], Yields are generally >95%, except for 4-nitrobenzyl alcohol. Under the normal reaction conditions, saturated primary alcohols are not... 

Selected examples of the oxidation of alcohols with Fremy s salt... 

The submitters report that approximately half of the nitrosodisulfonate radical had decomposed after the solution was stored at 0° for 2 weeks. They report the following procedure for the isolation of Fremy s salt (dipotassium nitrosodisulfonate). 

Caution Fremy s salt may decompose spontaneously in the solid stated... 

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