Of anhydrides to lactones

Regioselective hydrogenation of anhydrides to lactones. The last step in the synthesis of arylnaphthalene lignans is usually selective hydrogenation of an an-... 

Arene(tricarbonyl)chromium complexes, 19 Nickel boride, 197 to trans-alkenes Chromium(II) sulfate, 84 of anhydrides to lactones Tetrachlorotris[bis(l,4-diphenyl-phosphine)butane]diruthenium, 288 of aromatic rings Palladium catalysts, 230 Raney nickel, 265 Sodium borohydride-1,3-Dicyano-benzene, 279 of aryl halides to arenes Palladium on carbon, 230 of benzyl ethers to alcohols Palladium catalysts, 230 of carboxylic acids to aldehydes Vilsmeier reagent, 341 of epoxides to alcohols Samarium(II) iodide, 270 Sodium hydride-Sodium /-amyloxide-Nickel(II) chloride, 281 Sodium hydride-Sodium /-amyloxide-Zinc chloride, 281 of esters to alcohols Sodium borohydride, 278 of imines and related compounds Arene(tricarbonyl)chromium complexes, 19... 

Reduction of Cyclic Anhydrides to Lactones and Acid Derivatives to Alcohols... 

Results of reductions of cyclic anhydrides to lactones with sodium amalgam or with zinc are inferior to those achieved by complex hydrides [1020]. However, 95.6% yield of phthalide was obtained by reduction of phthalimide with zinc in sodium hydroxide [1021]. 

For the reduction of cyclic anhydrides to lactones, see page 1677, Section 2. 

Reduction of anhydrides to y-lactones. Carboxylic acid anhydrides are reduced by homogeneous hydrogenation catalyzed by this ruthenium complex... 

Acid derivatives are also reduced by L1A1H4. Reduction of the highly reactive acid chlorides 2 and acid anhydrides27 is rapid. Partial reduction of aromatic anhydrides to lactones has been reported by controlling the stoichiometry of L1A1H4 and the anhydride.28 In most cases, however, complete reduction to the diol... 

Catalytic enantioselective reductive desymmetrisation of achiral and meso-compounds, in particular, transformations of imides to lactams or lactones, anhydrides to lactones, and ring-opening of oxacycfic rings 13CC10666. 

Basic catalysts other than alkali acetates have been employed in the Perkin reaction thus salicylaldehyde condenses with acetic anhydride in the presence of triethylamine to yield coumarin (tlie lactone of the cis form of o-hydroxy-cinnamio acid) together with some of the acetyl derivative of the trans form (o-acetoxycoumaric acid) ... 

The principles set forth above account reasonably well for the course of bifunctional condensations under ordinary conditions and for the relative difficulty of ring formation with units of less than five or more than seven members. They do not explain the formation of cyclic monomers from five-atom units to the total exclusion of linear polymers. Thus 7-hydroxy acids condense exclusively to lactones such as I, 7-amino acids give the lactams II, succinic acid yields the cyclic anhydride III, and ethylene carbonate and ethylene formal occur only in the cyclic forms IV and V. 

Another approach to improve the color formation properties of Malachite Green lactone has been the introduction of nitrogen atoms into the phthalide ring. Thus, condensation of pyridine-2,3-dicarboxylic acid anhydride with dimethylaniline in the presence of zinc chloride has been shown54 to yield a mixture of the 4- and 7-azaphthalides 11 and 12. 

In analogy to the original preparation of Malachite Green lactone, pyromellitic anhydride has also been reacted with N, Ar-di me thy laniline in a zinc chloride melt to yield mixtures of the bisphthalides 29 and 30.109 However, far superior yields were obtained if reaction was carried out in two steps, as described in Scheme 12. The initial condensation was carried out... 

The first examples of a homogeneous reduction of this type were reported in 1971. Cobalt carbonyl was found to reduce anhydrides such as acetic anhydride, succinic anhydride and propionic anhydride to mixtures of aldehydes and acids. However, scant experimental details were recorded [94]. In 1975, Lyons reported that [Ru(PPh3)3Cl2] catalyzes the reduction of succinic and phthalic anhydrides to the lactones y-bulyrolaclone and phthalide, respectively [95], The proposed reaction sequence for phthalic anhydride is shown in Scheme 15.15. Conversion of phthalic anhydride was complete in 21 h at 90 °C, but yielded an equal mixture of the lactone, phthalide (TON = 100 TOF 5) and o-phthalic acid, which is presumably formed by hydrolysis of the anhydride by water during lactoniza-tion. Neither acid or lactone were further hydrogenated to any extent using this catalyst system, under these conditions. 

Succinic anhydride is clearly hydrogenated more readily than the acid, as was the case with phthalic acid (Scheme 15.17), but faster absolute rates were observed in the hydrogenation of o-phthalic acid and phthalic anhydride to phtha-lide. In these reactions, the problem of anhydride hydrolysis is less significant as the acid can also be reduced to the same lactone product... 

The cyclic anhydrides are reduced to lactones just by keeping the compound in contact with NaBH4, at 0° for 1 hour in the medium of dimethyl formamide. 

Reductions of anhydrides of monocarboxylic acids to alcohols are very rare but can be accomplished by complex hydrides [55, 99]. More frequent are reductions of cyclic anhydrides of dicarboxylic acids, which give lactones. Such reductions were carried out by catalytic hydrogenation, by complex hydrides and by metals. 

A series of solid-state reactions has been explored by Kaupp et al., in which gaseous amines were reacted with aldehydes to give imines. Analogous reactions with solid anhydrides, imides, lactones or carbonates, and isothiocyanates were used to give, respectively, diamides or amidic carboxylic salts or imides, diamides, carbamic acids, and thioureas [24]. In general the yields were found to be quantitative. Ammonia and other gaseous amines, in particular methyl-amine, have also been shown to aminolyse thermoplastic polycarbonates [25]. 

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