Epoxides, reaction with ethanol

Treatment of the epoxide (28) with ethanolic solution of PhSH containing KOH afforded the aldol product (31), which was believed to form via the nucleophile promoted retro-aldolization and subsequent aldolization reactions 14). 

Reaction of Epoxidized Esters with Alcohols. Alcoholysis study of epoxidized RME with ethanol and heptanol was condueted to determine the best eleavage conditions of the oxirane group acid catalysts (zinc chloride, PTSA) and a basic catalyst (sodium methylate) were tested. The results are reported in Tables 9 and 10. As expected, no cleavage of the oxirane group occurred when no catalyst or basic catalyst was used at temperatures <100°C. 

A recent oommtiruo tion by Gritter and Wallace discloses initiation of a study of the free-radical chemistry of epoxides Under the influence of U t-butoxy radicals, formed by thermal decomposition of di-lerf-butyl peroxide, propylene oxide is believed to yield an epoxy radical as shown in Eq. (3). The latter undergoes Isomerization to CHsCOCH - and further reaction with unreaoted propylene oxide or other available substrates, such as 1-octene, toluene, oyolohexene, and ethanol,fl7a as shown in Eq. (3). 

Table 2. Relative rate constants for the reaction of epoxides with ethanol at 50 °C. 471 (Reproduced by courtesy of Marcel Dekker, Inc.)...

Cyclopropen-1-yl sodium derivatives are also readily prepared. Thus reaction of cyclopropene with one equivalent of sodium amide in liquid ammonia leads to 1-sodiocyclopropene which is alkylated by haloalkanes 77,78 reacts with ketones to produce tertiary alcohols and opens epoxides to produce 2-cyclopropenyl-ethanols in moderate to good yields79). Moreover, on reaction with two equivalents of base followed by haloalkane, 1,2-dialkylated species are obtained sequential reactions can also be used to produce unsymmetrically substituted cyclopropenes78). Reaction with a deficiency of sodium amide can also cause addition of the cyclopro-penyl anion to unreacted cyclopropene, leading to products derived from the 2-cyclo-propylcydopropen-l-yl anion and to 1,2-dicyclopropylcyclopropene 77). 

Reactions with Nucleophiles. The epoxide is, by far, the more reactive site and a wide variety of nucleophiles have been used (eq 2) to open the ring at C-3 such as HCl (96%), HOAc (>50%), H2S (65% as cyclized product 3-thietanol), HCN (66%), ethanol (90%), t-butanol (86%), phenyl or benzyl thiol (99% or 93%, respectively), and phenyl selenide (generated in situ from the diselenide and sodium hydroxymethyl sulfite) (>55%). If desired, the epoxide is easily formed from the chlorohydrin by treatment with excess KOH or Et3N. 

The cyclization in Step B is an improvement of Butler s procedure for the synthesis of which employs less convenient reagents, KNH and l-bromo-3-chloroacetone acetal. Beside the acetals derived from neopentyl glycol, those derived from ethanol, 1,3-propanediol and 2,4-pentanediol have been synthesized by the present method. The second part of Step B involves the formation and the electrophilic trapping of cyclopropenyl anion 2, which is the key element of the present preparations. Step B provides a simple route to substituted cyclopropenones, but the reaction is limited to alkylation with alkyl halides. The use of lithiated and zincated cyclopropenone acetal, on the other hand, is more general and permits the reaction with a variety of electrophiles alkyl, aryl and vinyl halides, Me3SiCl, Bu3SnCl, aldehydes, ketones, and epoxides. Repetition of the lithiation/alkylation sequence provides disubstituted cyclopropenone acetals. 

D-Glucose ([52], Fig. 9) has served as an intriguing educt for preparation (31) of the Corey lactone equivalent [59] (32). The iodo compound [53] was readily available from glucose in four steps. Reductive fragmentation, induced by zinc in ethanol, gave the unsaturated aldehyde [54]. Reaction with N-methylhydroxylamine was followed by a spontaneous nitrone cycloaddition to provide the oxazolidine [55]. Catalytic reduction of the N-O bond was accompanied by the unexpected loss of tosylate and aziridine formation. Olefin formation from [56] via the N-oxide and chain extension gave acid [57]. lodolactonization and tri-n-butyltin hydride reduction in the standard fashion led to lactone [58]. After saponification of the benzoates, stereoselective epoxide formation gave epoxy lactone [59]. 

The most direct way to prepare VO(acac)2 is by the reaction of vanadyl sulfate with a source of the ligand. Vanadium(V), such as V205, can be reduced to vanadium(IV) by ethanol solvent in the presence of sulfuric acid. Reaction with acetylacetone in sodium carbonate yields the desired product. The synthesis we will use produces the complex in high yield directly in a system that can visually shed light on the active catalyst species in the epoxidation of olefins, Figure 9.4. 

A mixture of epoxides 118, 119, and 120, accompanied by some additional products, results from the complex reaction of epoxide 111 with sodium hydroxide in aqueous ethanol.739... 

Cleavage of 2,3-epoxy halidesA zinc-copper couple, prepared by sonication of zinc powder and Cui in aqueous ethanol, cleaves epoxy halides to a radical that rearranges to an allylic alcohol. Since the epoxy halide is prepared by epoxidation of an allylic alcohol (m-chloroperbenzoic acid) followed by reaction with P(ChH5)3 and CBr4, the reaction effects 1,3-transposition of the hydroxyl group. 

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