Lactones, hydrolysis dioxide

A dihydro version of the pyranoindoI-3-one has also been used as a precursor of an indole quinodimethane, as the result of thermal loss of carbon dioxide <89TL7289, 93T439>. The dihydro compounds can be prepared effectively from the pyranoindolones by a sequence of lactone hydrolysis, carbonyl reduction and relactonization. They can then be decomposed thermally in the presence of suitable dienophiles such as maleimides, quinones, or unsaturated ketones or esters. For example, the dihydroindolone (309) in its thermal reaction with iV-phenylmaleimide gives the tetracyclic adduct (310) (Scheme 93). 

Several total syntheses of antirhine (11) and 18,19-dihydroantirhine (14) have been developed during the last decade. Wenkert et al. (136) employed a facile route to ( )-18,19-dihydroantirhine, using lactone 196 as a key building block. Base-catalyzed condensation of methyl 4-methylnicotinate (193) with methyl oxalate, followed by hydrolysis, oxidative decarboxylation with alkaline hydrogen peroxide, and final esterification, resulted in methyl 4-(methoxycar-bonylmethyl)nicotinate (194). Condensation of 194 with acetaldehyde and subsequent reduction afforded nicotinic ester derivative 195, which was reduced with lithium aluminum hydride, and the diol product obtained was oxidized with manganese dioxide to yield the desired lactone 196. Alkylation of 196 with tryptophyl bromide (197) resulted in a pyridinium salt whose catalytic reduction... 

The naphthalene-catalyzed (2.5%) lithiation of phthalan 330 (or its substituted derivatives ) in THF at room temperature allowed the preparation of the functionalized benzyllithium intermediate 331, which reacted with electrophiles at —78°C to give, after hydrolysis, the corresponding functionalized benzyl alcohols 332 (Scheme 97). When carbon dioxide was used as the electrophilic reagent, the corresponding 5-lactone was directly obtained . When carbonyl compounds were used as electrophiles, the cyclization of the resulting products 332 under acidic conditions (85% H3PO4) allows the synthesis of substituted isochromans. 

The controversy centered, on the structure of the free acids which were obtained from the esters by hydrolysie,and the question was not easily settled for apparently the reactions of the compound could be interpreted in two ways. In perfect accord with the unsaturated formula the acid added hydrobromic acid easily1 to give a product wnich was shown to be CKatJr-CHa-CH< ) ) on heating the vlnaconic acid", carbon dioxide was evolved and a monobasic acid and lactone CHa - CH - CHs were obtained. Tne forma-... 

The oxidation and subsequent hydrolysis of starch to a-D-glucofuran-urono-6,3-lactone has been studied nitric acid alone, or in combination with nitrites, and nitrogen dioxide, have been examined as oxidants. Good results were obtained for oxidations with nitric acid in the presence of formic acid. A number of patents have been issued on these topics (Ref. 1, pp. 1137, 1138). Treatment of methyl /1-D-glucopyranoside with liquid nitrogen dioxide for 5 h at 12 °C afforded mostly D-glucaric acid, and three isomeric hexopyranosiduloses accounted for an additional 6% of the products.119... 

In most cases, uronic acids are liberated from acidic polysaccharides by hydrolysis leading to irreproducible concomitant formation of lactones. Several methods to circumvent this problem have been published describing conversion of the uronic acid into methyl esters followed by reduction with borohydride or borodeuteride reagents and subsequent hydrolysis and GC-MS detection [129]. Other techniques are based on the liberation and quantification of carbon dioxide. Direct determination of uronic acid residues in hydrolyzates has frequently been performed according to colorimetric assays, which are rather insensitive and have thus mostly been replaced by high-performance anion exchange chromatography (HP-AEC) methods [130-132]. 

Electroreduction of benzal chloride in the presence of carbon dioxide in DMF solvent gives very low yield of phenylacetic acid (131) (equation 70). The study suggests that the monoanion adds C02 to yield intermediate a-chlorophenylacetate which forms a-lactone. The acid is obtained following hydrolysis of the a-lactone by adventitious moisture in the DMF as shown in Scheme 910. 

One veiy useful transfomiation of these adducts is given in equation (7S). Hydrolysis of the diester to the diacid, followed by bis-decaiboxylation either by a double Cuitius rearrangement or oxidatively with ceric artunonium nitrate,yields an unsaturated lactone. This overall sequence is equivalent to effecting a Diels-Alder reaction wiA carbon dioxide, which is unreactive as a dienophile. 

With the necessary carbons present in (49), it can be seen that the scheme of oxidation of the allylic methyl group to the aldehyde level (selenium dioxide), and a reduction of the coumarin with concommitant hydrolysis (zinc/acetic acid), afforded the hydroxy-aldehyde-acid intermediate (57), which expectedly and spontaneously cyclized to the tricyclic lactone (55) under the conditions of the reaction. 

Although, under neutral and alkaline conditions, cellulose, methyl p-gluco-pyranoside and methyl p-eellobioside react with chlorine predominantly via formation of hypoehlorites (see Seetion 6.6.1.1), in acid (pH <2), when radical reactions are suppressed by addition of chlorine dioxide, the products are exclusively glueono-5-lactone (and some cellobionolactone from the cello-bioside), in aeeord with hydride abstraction followed by hydrolysis (Figure 6.60)." ... 

Carboxylation has also been seldom used especially for the constmction of various spiro-8-lactones. Rieke et al. have developed a direct synthesis of spiro-8-lactones from conjugated dienes and epoxides [114,115] (Scheme 67). Treatment of 1,2-bis (methylene)-cyclohexane-magnesium reagent derived from diene 306, with an excess of ethylene oxide, gave intermediate 307, which upon reaction with carbon dioxide and hydrolysis afforded the spiro-8-lactone 308. 

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