Hydroxyalkylation 3-Hydroxyalkyl mercury acetates

An acid-base reaction transfers a proton to another water molecule (or to an acetate ion). This step produces the (hydroxyalkyl)mercury compound. 

When (/3-hydroxyalkyl)mercury(II) acetates are treated with NaBH4 and no additional reagent, they first form (( - h y d roxy a Iky 1) me rcu ry (II) hydrides. These decompose via the chain reaction shown in Figure 1.12 to give a mercury-free alcohol. Overall, a substitution reaction R—Hg(OAc) — R—H takes place. The initiation step for the chain reaction participating in this transformation is a homolysis of the C—Hg bond. This takes place rapidly at room temperature and produces the radical Hg—H and a /3-hydroxylated alkyl radical. As the initiating radical, it starts the first of the two... 

Fig. 1.12. NaBH4 reduction of (/3-hydroxyalkyl)mercury(II) acetates to alcohols and radical fragmentation of (j3-hydroxyalkyl)mercury (II) hydrides.

Fig. 1.13. NaBH4-mediated addition of (/3-hydroxyalkyl )mercury (II) acetates to an acceptor-substituted olefin.

Alkenes react with mercuric acetate in a mixture of tetrahydrofuran (THF) and water to produce (hydroxyalkyl)mercury compounds. These (hydroxyalkyl) mercury compounds can be reduced to alcohols with sodium borohydride. 

Tertiary amines form complexes with mercury(II) ion, which then give iminium ions by loss of a piotoa Addition of perchloric acid permits isolation of the iminium ion as the perchlorate salt and generally the more-substituted ion is favored (equation 14). Intramolecular trapping by a hydroxyalkyl group is also possible to form aminals (equation 15). The lactam products result from over-oxidation, which is promoted by heat. Basification on the other hand usually allows the isolation of enamines although hydroxyenamines have been obtained by reaction of enamines with mercury(II) acetate (equation 16), while dihydroaromatic systems undergo aromatization (equation 17). ... 

Thus, two groups of investigators reported that the irradiation of certain oxygen heterocycles having a hydroxyalkyl side chain in cyclohexane in the presence of (diacetoxyiodo)benzene and iodine at room temperature gave bis-spiroacetals in good yields (Scheme 30). Subsequent work showed that similar reaction conditions could be applied to the synthesis of a number of five- and six-membered cychc acetals from y- and e-hydroxyethers (Scheme 31). The formation of a cychc acetal was also found in the hypoiodite reaction of hydroxysteroid with mercury(ll) oxide and iodine (Scheme 32). 

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