(g)Hydroxylation of carbon–carbon double bonds with osmium tetraoxide proceeds with syn ad-dition of hydroxyl groups.The product is chiral but is formed as a racemic mixture containing equal amounts of the9R,10Sand 9S,10Rstereoisomers.(h)Hydroboration–oxidation gives syn hydration of carbon–carbon double bonds with a regio-selectivity contrary to Markovnikov’s rule. The reagent attacks the less hindered face of thedouble bond of a-pinene.(i)The starting alkene in this case is b-pinene. As in the preceding exercise with a-pinene, diboraneadds to the bottom face of the double bond.(j)The starting material is an acetal. It undergoes hydrolysis in dilute aqueous acid to give a
This is the end of the preview. Sign up
access the rest of the document.