Dissolving metals epoxides

Sterically hindered epoxides are sometimes easier to reduce by dissolving metals 2-methyl-2,3-epoxybutane gave, after treatment with lithium in ethylenediamine at 50° for 1 hour, 74% of 3-methyl-2-butanol and 8% of 2-methyl-2-butanol [659. ... 

The metal-NHs reductions of carbonyl groups are exceedingly fast reactions for the reaction of acetone with an ammoniated electron the rate is 9 x 10 M" s". Although many, particularly older, published experimental procedures for the metal-NHs reduction of ketones employ prolonged reaction times with excess metal, these conditions are unnecessarily harsh. The reactions of carbonyl compounds with metals in NH3 are effectively instantaneous and by using short reaction times it appears that reduction of terminal alkenes and disubstituted alkynes can be avoided.In addition to the functional groups mentioned above, alcohols, amines and ethers, other than epoxides, are usually stable to reductions of aldehydes and ketones by dissolving metals. " ... 

Although Smh is more chemoselective than traditional dissolving metal reagents, it does react with sulfoxides, epoxides, the conjugated double bonds of unsaturated ketones, aldehydes and esters, alkyl bromides, iodides and p-toluenesulfonates. It does not, however, reduce carboxylic acids, esters, phosphine oxides or alkyl chlorides. In common with most dissolving metal systems, ketones with an a-hetero substituent suffer loss of the substituent rather than reduction of the carbonyl group. ... 

Mesylates, which tend to undergo O—S scission with dissolving metals, were reduced electrochemi-cally in DMF. Yields of 70-85% were reported under conditions which left esters, nitriles and epoxides unchanged. The conversion of (30) to (31) again indicated a carbanionic intermediate. 

Table 8 Reduction of Epoxides with a Dissolving Metal ...

Reactions of carbon-carbon % bonds dissolving metal reductions, conversions to alcohols and enantiomerically pure alcohols, chemo- and enantioselective epoxidations, procedures for cleavage of carbon-carbon double bonds, and reactions of carbon-carbon triple bonds... 

One of die most popular reactions in organic chemistry is dissolving metal reductions [1-3], Two systems are frequently used - sodium dissolved in ammonia with alcohol and lithium dissolved in alkylamines [4]. Although calcium is seldom used, it has been successfully applied to the reduction of a variety of compounds and functional groups [5], including aromatic hydrocarbons, carbon-carbon double and triple bonds, benzyl ethers, allyl ethers, epoxides, esters, aliphatic nitriles, dithianes, als well as thiophenyl and sulfonyl groups. 

The procedure developed for the decyanation of secondary nitriles has been extended to a,P-unsaturated nitriles. The reaction of a-unsubstitutcd a,p-unsaturatcd nitriles with LDA in THF/HMPA results in the abstraction of a y-hydrogen from a methylene site to afford a delocalized anion. Trapping this anion at the a-position by dimethylation ° ° followed by reduction-elimination with dissolving metals leads to tetrasubstituted alkenes (Scheme 6.56). ° Epoxidation of the... 

Baeyer-Villiger oxidation (p. 853) catalytic hydrogenation (p. 844) chemoselective reaction (p. 848) dissolving-metal reduction (p. 846) enantioselective reaction (p. 857) epoxidation (p. 855) functional group interconversion (p. glycol (p. 858)... 

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