Reduction to lactones

Anhydrides—Continued reduction to alcohols, 155 reduction to lactones, 535 Arenes, see Hydrocarbons, aromatic Amdt-Eistert reaction, 433, 487, 573 Aryl esters. Fries rearrangement, 344 hydrolysis, 169 preparation, 169 Aryl halides, see Halides Atyloxy acids, preparation, by aceto-acetic ester synthesis, 430 by malonic ester synthesis, 429 from atyloxy alcohols, 419 from atyloxy cyanides, 414 preparations listed in table 48, 460 Aryloxy acyl halides, preparation, 547 preparations listed in table 61, 553 Aryloxy esters, preparations listed in table 55, 516... 

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

The sulfonyl substituent can be removed by reduction after the ring closure (see Section 5.6.2). Other appropriate reactants are a-phenylthio nitriles, which can be hydrolyzed to lactones.124... 

MISCELLANEOUS BENZOHETEROCYCLES Partial reduction of lactone 166 (using for example diisobutylaluminum hydride in the cold) affords lactol 167. Condensation with nitromethane leads to the corresponding alkylated tetrahydrobenzopyran 170. The sequence probably starts by aldol reaction of the hydroxylactone form of the lactol (168) with nitrome thane to give the vinyl nitro intermediate 169 ... 

The structure of narlumidine (119) was established by Dasgupta et al. (117,119) on the basis of spectral data, particularly by comparison with spectra of bicucullinine (108), and also on chemical grounds. On hydrolysis followed by oxidation-methylation, narlumidine (119) was converted to ester 147, which was also obtained from 108 by N.O-methylation. Sodium borohydride reduction gave lactone 145, identical to the lactone obtained from 108. 

The formyl group in orthoformylselenophenecarboxylic acids on reduction to an hydroxymethyl group undergoes ring closure to lactones.100 To obtain 2,4-disubstituted selenophenes, 4-bromo-2-formylselenophene was prepared by the swamping catalyst method.101 Selenopheno[2,3-b]thiophene derivatives may be prepared from compound 84.102 Another route to substituted... 

Coumarin (7.88) is a well-known 6-lactone (six-membered ring) of natural origin found in various preparations such as some tobaccos, alcoholic beverages, and cosmetics. Besides reactions of oxidation, reduction, and conjugation, coumarin is also subject to lactone hydration in vivo and in the presence of microsomes [170-174], The resulting metabolites include ortho-coumaric acid (7.89) formed directly from coumarin, 3-(2-hydroxyphenyl)-propionic acid (7.91) formed following reduction of coumarin to dihydrocou-... 

In Yamada s retrosynthetic analysis (Scheme 11), elisabethin C (26) is traced back to lactone 64 which would be converted into 26 by deoxygenation and chain elongations. Key intermediate 64 could be obtained by a stereoselective Dieckmann cyclization. The required ester lactone precursor 65 would be accessible from 66 by a series of oxidation reactions. Further disconnection would lead to commercially available (+)-carvone (67). Stereoselective successive alkylation of 67 and reduction of the enone should deliver 66 [30]. 

Reductive y-lactone ring opening, with concomitant desilylation at the tertiary position by LiAlH4, gave triol 17 in 80% yield. Finally, acetonide formation followed by oxidation with tetra-n-propylammonium perruthenate/A-methylmorpholine / /-oxide oxidation, led to the target aldehyde 19 in 80% overall yield. 

The dimerization of aldehydes to form esters is a completely atom-efficient process known as the Tishchenko reaction, which involves no net oxidation or reduction. Suzuki, Katoh, and coworkers have used complex 77 to catalyze the Tishchenko reaction of a range of aldehydes, including dihydrocinnamaldehyde 91 and benzaldehyde 14 (Scheme 22) [81]. The same catalyst has been used for an intramolecular variant of the reaction, where keto-aldehyde 92 isomerizes to lactone 93 via an intramolecular Tishchenko reaction. The oxidized product is formed as a by-product,... 

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