Benzyl ethers acetoxylation

Asymmetric epoxidation of 10a under standard conditions yields the crystalline epoxy alcohol 2a in 95% ee (91% chemical yield). Treatment of 9a with thioanisol in 0.5N NaOH, in rerf-butyl alcohol solution, gives -after protection of the hydroxyl groups as benzyl ethers- the sulfide a (60% overall yield) through an epoxide ringopening process involving a Payne rearrangement. Since the sulfide could not be hydrolysed to the aldehyde 7a without epimerisation at the a-position, it was acetoxylated in 71% yield under the conditions shown in the synthetic sequence (8a... 

The three isomeric monosulphates of cholic acid are described. Syntheses of the four monoglucuronides of oestra-l,3,5(10)-triene-3,15a,16a,17/8-tetrol were achieved by carefully chosen routes via suitably protected intermediates. The 2- and 3-monomethyl ethers of 2,16/3-dihydroxy-oestrone and -oestradiol have been prepared from 2-hydroxyoestrone, protected at the phenolic hydroxy-groups by forming the 3-benzyloxy-2-methoxy- and 2-benzyloxy-3-methoxy-derivatives, respectively. Acetoxylation at the 16/3-position used the reaction between lead tetra-acetate and the A -enol acetates (516) and (517) the benzyl group was removed reductively as the final step, leading to the monomethyl ethers (518) and (519)." "... 

The or//io-palladation of 3,4-dioxygenated benzylic tertiary amines by lithium tetrachloropalladate can be directed exclusively to either C-2 or C-6. Substitution at C-6 prevails when AcO, methylenedioxy, PhCH20, methoxymethyl ether, or HO substituents are attached to C-3, whereas palladation occurs exclusively at C-2 when C-3 bears methylthiomethyl ether or phenylthiomethyl ether substituents. The resulting organopalladium compounds are crystalline solids, stable to air and moisture, and can readily be carbonylated, alkylated, arylated, Kinetic studies of the acetoxylation of arenes by potassium peroxydisulphate and acetic acid in the presence of (2,2 -bipyridyl)palladium(ii) acetate catalyst have led to a revision of the mechanism. The reaction is now thought to proceed via... 

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