Azidomercuration

Hydrazoic acid can be added to certain Michael-type substrates (Z is as defined on p. 975) to give 3-azido compounds. The reaction apparently fails if R is phenyl. Ammonia also adds to enol ethers CH2=CHOR to give CH3—CH(OR)N3, and to silyl enol ethers, but it does not add to ordinary alkenes unless a Lewis acid catalyst, such as TiCU, is used, in which case good yields of azide can be obtained. Ammonia can also be added indirectly to ordinary alkenes by azidomercuration, followed by demercuration, analogous to the similar procedures mentioned in... 

The formal addition of H—N3 across C—C double bonds can also be brought about via azidomercuration-demercuration, a process recently reviewed.267 In the presence of NaN3, Hg(OAc)2, Hg(02CCF3)2 or Hg(N03)2, in aqueous THF, methanol or DMF, alkenes undergo azidomercuration (equation 188).268-... 

Only two dienes, and no alkynes, have been subjected to azidomercuration (equations 189 and 190).275-277... 

An example of intramolecular aminomercuration has been reported by Weimeb as part of the synthetic strategy to the tricyclic nucleus of madangamine A - an alkaloid that shows cytotoxicity toward a number of tumor cell lines (equation 15). Pearson has recently reported the first example of an azidomercuration involving aliphatic azides (see equation 16) according to a protocol that exhibits wider applicability and is, therefore, more convenient than the analogous acid-promoted Schmidt reaction. ... 

Azldomercuratlon. Azidomercuration of the unsaturated sugar 1 with NaN, and mercury(II) acetate proceeds in low yield (20%). However, use of NaN, and... 

Heathcock has observed that secondary and tertiary alkyl azides are obtained in good yields from terminal alkenes, but that non-terminal alkenes are relatively unreactive, except where reactivity is enhanced by steric strain as in norbornene. The order of reactivity in this reaction is similar to that in hydroxymercuration. A correlation between the reactivity sequence for azidomercuration and the known order of alkene-Ag stability constants was also apparent zmd Heathcock therefore proposed a mechanism which entails a rapid equilibrium involving the ion 197 which affords the organomercury... 

Application of the azidomercuration-demercuration procedure to the 5-ene (9) gave the 6- and 5-azides (10) and (11) in the ratio 1 4 (Scheme 1). The synthesis of azido-sugars via 2,3-anhydro-furanosides has been reported. Methyl 2,3-anhydro-0 -D-lyxofuranoside (12) gave the 3-azide (13) in 95% yield, and its 5-0-tosyl ester (14) gave the 3,6-diazide (15) in 84% yield. In contrast, the 2,3-anhydro-riboside (16) gave a mixture of the 2- and 3-azides (17) and (18) in the ratio 3 2. However, substitution at C-5 of (16) resulted in steric hindrance of the approach to C-3 and consequently the 5-tosylate (19) afforded the 2,6-... 

Unsaturated hydroperoxides, e.g. (E)-PhCH =CHCH200H, undergo cycloperoxymercuration on treatment with Hg(OAc)2 and/or Hg(NOj)2 (e.g. to/ra s-PhCHOOCH2CHHgX). Azidomercuration of dimethyl tricycle[4.2.0.0 ]deca-3,7,9-triene-9,10-dicarboxylate has been studied. Methoxymercuration of PhC CPh provides PhC(HgCl)2CPh(OMe)2 however, under die reaction conditions, this adduct may be transferred into cis-ClHgCPh=CPhOMe. 

An improved method for the azidomercuration of alkenes with mercuric trifluoroacetate has been described.When applied to unsaturated carbohydrates it provides, after demercuration and reduction, a high-yielding synthesis of amino-sugars. 

The first successful approach was reported by Heathcock in 1969 using mercury(ll) salts. The reaction proceeds via an olefin azidomercuration followed by a reductive demercuration in the work-up. The azides derived from terminal olefins were obtained in 50-88% yield with good Markovnikov selectivity, while non-terminal olefins gave lower yields (Figure 4.2). An obvious drawback of this procedure is the use of a stoichiometric amount of mercury salts. This procedure also leads to the formation of potentially explosive Hg(N3)2. Nevertheless, this method is unique and reliable for the hydroazidation of monosubstituted non-activated olefins. 

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