Diazonium ions conversion

An important reaction of aryl diazonium ions is their conversion to phenols by hydrolysis... 

Diazotization (Section 24.8) The conversion of a primary amine, RNH2, into a diazonium ion, RN2+, by treatment with nitrous acid. 

The diazotization of amino derivatives of six-membered heteroaromatic ring systems, particularly that of aminopyridines and aminopyridine oxides, was studied in detail by Kalatzis and coworkers. Diazotization of 3-aminopyridine and its derivatives is similar to that of aromatic amines because of the formation of rather stable diazonium ions. 2- and 4-aminopyridines were considered to resist diazotization or to form mainly the corresponding hydroxy compounds. However, Kalatzis (1967 a) showed that true diazotization of these compounds proceeds in a similar way to that of the aromatic amines in 0,5-4.0 m hydrochloric, sulfuric, or perchloric acid, by mixing the solutions with aqueous sodium nitrite at 0 °C. However, the rapidly formed diazonium ion is hydrolyzed very easily within a few minutes (hydroxy-de-diazonia-tion). The diazonium ion must be used immediately after formation, e. g., for a diazo coupling reaction, or must be stabilized as the diazoate by prompt neutralization (after 45 s) to pH 10-11 with sodium hydroxide-borax buffer. All isomeric aminopyridine-1-oxides can be diazotized in the usual way (Kalatzis and Mastrokalos, 1977). The diazotization of 5-aminopyrimidines results in a complex ring opening and conversion into other heterocyclic systems (see Nemeryuk et al., 1985). 

In Sections 5.2 and 5.3 it was shown that experimental data are consistent with a direct rearrangement of the (Z)- to the (ii)-diazohydroxide rather than with a recombination after a primary dissociation of the (Z)-isomer into a diazonium ion. Positive evidence for direct formation of the (ii)-diazohydroxide from the diazonium ion and a hydroxide ion (or water) is still lacking (see Scheme 5-15 in Sec. 5.2). For diazo ethers, however, Broxton and Roper (1976) came to the conclusion that there is no direct (Z) >(E) conversion, but rather that in the system ArNj + OCH3/(Z)-diazo ether/(Zi)-diazo ether the (Z)-ether is the kinetically determined product and the (iE )-isomer the thermodynamic product, as shown in Scheme 6-3. 

In the pH range 3.7-6.2, the kinetic equation does not contain a pH-dependent term this is consistent with a direct reaction of diazonium ions with neutral molecules of indole. At higher pH (6.2-8.6) an initial increase in rate is observed, in spite of the partial conversion of the diazonium chloride into the unreactive diazohydroxide. Probably an alternative path involving the conjugate base of indole also becomes operative. 

Atomic motions involved in the conversion of a contact ion-pair between an aromatic diazonium ion and a nucleophile into the E and the Z-isomer of the covalent diazo-compound... 

Fluorodikylammes react with nitrous acid to produce the corresponding unstable fluoroahphatic diazonium ions Placement of the tnfluoromethyl group at a carbon position a, P, or Y to a diazonium ion was used to probe the inductive effect on the chemistry of the transient carbocation resulting from dediazoniation [7] If the fluoroalkyl group is bound to the same carbon as the amino group, conversion to the more stable diazo compound occurs For example, 4-diazo-1,1,1,2,2-pentafluoro-3-pentafluoroethyl-3-tnfluoromethylbutane is obtained from the reaction of the poly-fluoroalkylamine salt with sodium nitnte [S, 9] (equation 8)... 

Brase and coworkers were the first to introduce triazene linkers for use in SPOC in a seminal report in 2000 [18]. They found immobilized diazonium ions have high stability, which enabled their application as linkers and scavengers. Their synthesis involves the reduction of 3-amino-6-chlorobenzoic acid, which was subsequently coupled onto a Merrifield resin via standard etherification. Subsequent conversion of the amino group into a diazonium salt generated the supported diazonium tet-rafluoroborate, which was found to sequester amines (Scheme 8.12). 

Reviews this year include the collation of evidence in favour of the o-bridged 2-norbornyl cation,the use of aliphatic diazonium ions as means for the production of carbocations, terpene rearrangements in superacid media,and the formation of carbocations by the silver-assisted reactions of chloroformates. A convenient procedure, using syringe techniques, has been described for the preparation of ca. IM solutions of alkyl cations in SbF5-S02ClF from suitable precursors that are soluble in SO2CIF at —78 Since conversions are essentially quantitative, the... 

The mechanism by which this mixture of products is formed involves formation of a diazonium ion. The conversion of a primary amine to a diazonium ion is called diazotization. 

Analogs of (I) in which the benzyl group was replaced by a methyl or ethyl group showed almost no inhibition although their hydrolysis is enzyme catalyzed. This lack of inhibition may result from the conversion of intermediate alkyl diazonium ions into di azoalkanes. 

We recall that breaking both the O—H bond of an alcohol and the C—H bond at the carbon atom bearing the hydroxyl group is an oxidation reaction or an a-ehmtnation reaction. Amines can be similarly oxidized, but the products are sensitive to reaction conditions, and synthetic applications of this chemistry are limited. We recall, for example, that imines are very reactive. In this chapter, we consider only one type of reaction that can be termed an oxidation. Nitrous acid (HNO2) is a mild oxidizing agent that generates intermediates that are oxidized relative to an amine. We have already seen some of this chemistry in the conversion of aromatic amines into aromatic diazonium ions (Section 13.8). We will expand on this reaction and related chemistry in this chapter for alkyl-... 

And finally, conversion of the amino group into a cyano group is achieved in two steps. First, para-isopropylaniline is treated with sodium nitrite and HCl, giving an aromatic diazonium ion, which is then treated with CuCN to give a Sandmeyer reaction that affords the desired product ... 

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