M-Diol monoesters

Resins s. Ion exchange resins Resolution s. Stereoisomers Resonance system s. No-bond resonance system Resorcinol monoesters s. m-Diol monoesters Resorcinols... 

In the first step, the peroxy acid adds to the carbonyl group of the ketone to form a peroxy monoester of a m-diol. 

A. Corma, M. Rodriguez, N. Sanchez and J. Aracil, in Process for the selective production of monoesters of diols and trials using zeolitic catalysts , EP, 1994. 

The epoxidation reaction is achieved most conveniently by employing m-chloroperbenzoic acid (or perbenzoic acid) in a solvent such as chloroform. The use of other peracids, such as peracetic acid or pertrifluoroacetic acid, give lower yields of the oxirane since the oxide may be readily cleaved to form the monoester of the diol (e.g. Section 5.4.5, p. 547). 

A spectroscopic study (i.r. and n.m.r.) of the monoesters of trifluoroacetic acid with the diols HO-CHa-CHa-OH, HO CHaCMea-OH, and HO CMea CMea OH has shown that with the pinacol ester (27), significant amounts of the cyclic tautomer (28) are present at equilibrium in various solvents (CCI4, 60% CsHe, 72% MeCN, 95% 1,4-dioxan, 95%) considerably smaller amounts of the corresponding trichloroacetate cyclic tautomer are present at equilibrium (CCU, 7% MeCN, 13%). ... 

The transformation of enantiomerically enriched 1,1,4-trisubstituted but-2-yne-l,4-diols (262) into 2,2,5-trisubstituted 3-acyloxy-2,5-dihydrofurans (267) with complete stereospecificity has been achieved by an Ag(I)-mediated rearrangement of the monoesters (263) to allenic intermediates (265), followed by Ag(I)-assisted cycUzation. A possible mechanism for the rearrangement and cyclization is shown in Scheme 66, in which the carbon-oxygen bond (b) in (266) is formed from the back side of the carbon-oxygen bond (a) in (264). A novel synthetic method has been developed for the rearrangement of 3-aryl-l,2-dialkynylallyl alcohols into m-enediynes under mild acidic conditions. The allylic rearrangement has been shown to involve an acid-catalysed isomerization step to convert the allyl alcohol into an allylic cation... 

Similarly as for prochiral substrates, many of the lipase-catalyzed asymmetrizations of meso compounds are accompanied by a second reaction step that usually enhances the enantiomeric excess of the product. This second step is a kinetic resolution. For example, in the hydrolysis of a m o-diester, die reaction usually does not stop at the monoester stage (Scheme 15). The two enantiomeric monoesters will react further giving the same me o-diol. This second step usually favors the minor monoester enantiomer and therefore leads to an increase of the enantiomeric excess of the major monc ster, but a decrease in the yield. This has been illustrated and described by Wang et al. for the lipase-catalyzed hydrolysis of meso-l,5-diacetoxy-cw-2,4-dimethylpentane [117]. The monoacetate was afforded in 89.7% e.e. 

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