Hydroxide, sodium dihydroxylation

Unger and coworkers [26] described the synthesis of FPS containing l,2-epoxy-3- pro-poxypropyl groups. Initially, polyethoxysiloxane (MW = 800) was prepared from TEOS by acid hydrolysis, which was further used in hydrolytic polycondensation with 1,2-epoxy-3-propoxypropyltriethoxysilane. Homogeneity of the reaction medium in the second stage was maintained by addition of sodium or ammonium hydroxide, so that the final product contained either 1,2-dihydroxyl-3-propoxypropyl or hydroxylamine functional groups. 

Yet another approach by Corey and Snider [43] utilised a novel allylic functionalisation of the acetal (37) with 7V-phenyltriazolinedione to give the intermediate (38), the A -methyl derivative of which afforded the hydrazine (39a) on dihydroxylation of the olefinic bond and hydrolysis of the lirazole moiety with potassium hydroxide. Hydrogenolysis then led to the amine (39b) which underwent ring contraction to (lOd) on treatment with sodium nitrite in aqueous acetic acid. 

One of the earliest known method of syn-dihydroxylation of alkenes is by treatment with dilute KMnO solution in presence of sodium hydroxide (Scheme 67). In fact the change in purple colour is the basis for the presence of double bond and this is known as Baeyer s test for unsaturation. 

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