Mechanism acid-catalyzed epoxide cleavage

Mechanism 8-10 Acid-Catalyzed Opening of Epoxides 362 8-14 Syn Dihydroxylation of Alkenes 364 8-15 Oxidative Cleavage of Alkenes 366 8-16 Polymerization of Alkenes 369 8-17 Olefin Metathesis 373... 

The acid-catalyzed hydrolysis of epoxides proceeds by either heterolytic cleavage of the carbon-oxygen bond to form a carbonium ion intermediate that subsequently reacts with water to form the diol (8, 1 mechanism) ... 

The synthesis of hydroxycarbamates from secondary aliphatic amines, C02 and epoxides has been found to be catalyzed by (5,10,15,20-tetraphenylporphinato) aluminum(III) acetate, AI(TPP)(02CCH3) [80], Scheme 6.14 illustrates the mechanism proposed for the catalytic process, which can be carried out under not severe conditions (293-343 K 0.1-5 MPa C02 pressure). The key step here is the insertion of epoxide into the Al-O bond of the A1-carbamate A (Scheme 6.14), which preliminarily forms by the reaction of A1(TPP)(02CCH3) with the amine and C02. Protolytic cleavage of the Al-alkoxide bond in the insertion product, C, by dialkylcarbamic acid regenerates the catalytkally active carbamato-species A and... 

Some bismuth(III) carboxylates catalyze the oxidative C-C bond cleavage of epoxides into carboxylic acids in a DMSO-O2 system (Scheme 14.109) [229], In the initial stage DMSO transfers an oxygen atom to epoxides activated by Bi(OCOR)3, producing a-hydroxy ketones [230]. a-Hydroxy ketones can be converted into carboxylic acids by O2 under bismufh(III) mandelate catalysis (Scheme 14.110). In the presence of catalytic amounts of Bi and Cu(OTf)2, 1,2-disubstituted epoxides are oxidized to a-diketones by a combination of O2 and DMSO (Scheme 14.111) [231]. The mechanism presumably involves two catalytic cycles fhe first oxidative ringopening to a-hydroxy ketones is catalyzed by Cu(OTf)2-DMSO, and the second oxidation to a-diketones is achieved by the Bi /Bi redox cycle under the action of O2. 

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