Ethyl levulinates, 5-substituted

Ethylenedioxybutyl)-3-trichloro-acetamido-l-cyclohexene, 58, 9, 11 Ethylene glycol, 56, 44 Ethyl a-fluoro-l-naphthaleneacetate, 57, 73 Ethyl 2-fluoropropanoate, 57, 73 3-Ethylhexane, 58, 3, 4 3-ETHYL-l-HEXYNE, 58, 1, 2, 3, 4 Ethylidenecyclohexane, 59, 46 Ethyliodide, 59, 133 Ethyl 2-iodo-3-nitropropionate, 56,65 Ethyl isocyanide, 55, 98 Ethyl isocyanoacetate, 59,184 l-Ethyl-4-isopropylbenzene, 55,10 Ethyl levulinates, 5-substituted, 58, 81 ETHYL 2-METHYL1NDOLE-5CARBOXY-LATE, 56, 72... 

Levulinic acid is known to react with aldehydes at carbon atoms adjacent to both the acid (a) and keto (P and 8) groups to form a mixture of the a-, P-, and 8- alkylidene or arylidene derivatives 11,12), With excess formaldehyde, levulinic acid is substituted with five or six hydroxymethyl (methylol) groups, and cyclization to a lactone occurred 18), These condensation reactions could be utilized to produce inexpensive resins from the crude ethyl levulinate obtained from waste particle board without distillation. Another reason for studying the reactions of the ester with aldehydes is to determine the potential for similar reactions occurring during the cellulose... 

In order to selectively obtain the a-substituted condensation products from levulinate esters, it is necessary to protect the ketone group. Ethyl levulinate reacts with one mole of ethylene glycol to form the cyclic ketal. Condensation of the protected ester with benzaldehyde gave the a-benzylidene ester in 73% yield (Figure 3). 

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... 

The introduction of the trimethylsilyl chloride trapping technique" led to improved yields in the case of simple aliphatic esters. The initial silylated products are easily isolated and can be converted into the acyloins simply and in high yield. For simple aliphatic esters the yields are in the range 56-92%. Use of trimethylsilyl esters, rather than simple alkyl esters, leads to faster reactions, but lower yields.Substituted esters which have been successfully used in the newer procedure include ethyl 2-ethylhexanoate (83%), ethyl trimethylsilylacetate (90%)," ethyl 3-trimethylsilylpropionate (65%)," ethyl phenylacetate (48%)," ethyl 3-phenylpropionate (79%)" and 2-(2-methoxycarbonylethyl)-2-methyl-l,3-dioxolane derived from levulinic acid (65%)." In the case of ethyl adamantane-l-carboxylate the yield using the newer procedure is reported to be inferior to that using the earlier procedure. 

Reactions with functionalized alkyl halides significantly enhance the range of application of alkyl [ C]acetoacetates. Alkylation of ethyl [3- C]acetoacetate with halo esters, for example, followed by acid-mediated ketonic cleavage opens access to labeled keto acids/esters, as demonstrated by the synthesis of the [4- C]levulinic acid (307) a y-keto acid. The latter has served as a key intermediate in the synthesis of the 2,3-substituted indole 308 . Step 2 in Figure 6.85, the ketonic cleavage, has recently been shown to be accelerated by a factor of 20 when the reaction is submitted to microwave heating. ... 

Figure 6.85 Use of ethyl [S-" C]acetoacetate in the synthesis ofy-[4d C]keto acids[4- C] (e.g., levulinic acid) and its application to the synthesis of a substituted [3- C]indole...

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