Oxidative bisdecarboxylation

The use of lead tetraacetate to carry out oxidative bisdecarboxylation of diacids has been found to be a highly useful procedure when used in conjunction with the Diels-Alder addition of maleic anhydride to dienes, the latter process providing a ready source of 1,2-dicarboxylic acids. The general pattern is illustrated in the reaction... 

Oxidative bisdecarboxylation.1 A new route to lactones is based on the ability of CAN to effect oxidative decarboxylation of a-hydroxymalonic acids to carboxylic acids (11, 143-144) and of a-alkoxymalonic acids to lactones. 

The oxidation decarboxylation of monocarboxylic acids is retarded by oxygen,708 but oxygen increases the yield of olefins in oxidative bisdecarboxylation of (9) - ... 

The oxidative bisdecarboxylation of a,/3-dicarboxylic acids is usually carried out with lead tetraacetate and pyridine, in benzene or acetonitrile as solvent, at 50-60° [procedure of Grob (1,554-555)]. However, these conditions are reported2 to be unsuccessful in some cases, for example with (1) (1,4-dimethoxycarbonyl-bicyclo[2.2.2]octane-2,3-dicarboxylic acid). The decarboxylation, however, is successful in refluxing benzene (45% yield)3 or can be conducted at room temperature in comparable yield if dimethyl sulfoxide or dioxane is used as solvent.4... 

Oxidative bisdecarboxylation. This reaction using the organometallic reagent lalhcr than lead tetraacetate was introduced by Trost and Chen. These... 

Oxidative bisdecarboxylation. An efficient recent synthesis of Nenitzescu s hydrocarbon (3) involves a Diels-Alder reaction followed by bisdecarboxylation with this Ni complex. Pb(OAc)4 is unsatisfactory for the latter step. The product (3) was also used for preparation of barrelene (4) in 24% yield from (1). 

Syntheses have been reported of barrelene (505) and of Nenitzescu s hydrocarbon (503) on a reasonable scale and without some of the difficulties that attend the previously published routes." " The preparation of (503) is of central importance, it being obtained by the oxidative bisdecarboxylation of the cyclo-octatetraene-maleic anhydride Diels-Alder adduct (502) with dicarbonylbis(triphenylphosphine)-nickel in diglyme at reflux. Cycloaddition of (503) to 2,5-dimethyI-3,5-diphenyl-cyclopentadienone in hot benzene afforded (504) and its endo-isomer. Photolysis of (504) yielded (505) in 24% yield from cyclo-octatetraene. The thermally labile benzene-maleic anhydride [4 + 2] cycloadduct (506) was obtained in similar fashion from (502). A review of the mechanisms of pyrolysis of (503) and a number of isomers and benzo-fused (CH) derivatives (collectively termed Nenitzescu s hydrocarbons) has appeared." ... 

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-... 

Addition of carboxylic acids to alkynes Acylation of aldehydes or ketones Bisdecarboxylation of malonic acids Oxidation of arylmethanes with CrOs and AC2O... 

Bisdecarboxylation of malonic acids 9-15 Oxidative decyanation of nitriles 9-16 Oxidation of activated or unactivated methylene groups 9-20 Oxidation of secondary alkyl halides and tosylates... 

The starting compound 251 was reduced to 252 with sodium borohydride. The latter was heated under reflux in 6% sulfuric acid in methanol to afford compound 253. Treatment of the latter with maleic anhydride at 170° for 3 hr afforded compound 254. Bisdecarboxylation of 254 with dicarbonyl bistriphenylphosphinenickel in anhydrous diglyme under nitrogen at reflux temperature for 6 hr afforded the olefin 255 in 69% yield (171). The latter was reduced with lithium aluminium hydride to the primary alcohol 256, which was oxidized to the aldehyde 257 with Ar,A -dicyclohexylcarbodiimide, dimethyl sulfoxide and pyridine in dry benzene. Treatment of the aldehyde 257 with an excess of the Grignard reagent prepared from l-bromo-3-benzyloxybutane afforded a mixture of diastereoisomers represented by the structure 258. 

Anodic dehydrogenations, e.g., oxidations of alcohols to ketones, have been treated in Sect. 8.1 and formation of olefins by anodic elimination of C02 and H+ from carboxylic acids was covered in Sect. 9.1. Therefore this section is only concerned with anodic bisdecarboxylations of v/odicarboxylic acids to olefins. This method gives usually good results when its chemical equivalent, the lead tetraacetate decarboxylation, fails. Combination of bisdecarboxylation with the Diels-Alder reaction or [2.2] -photosensitized cycloadditions provides useful synthetic sequences, since in this way the equivalent of acetylene can be introduced in cycloadditions. 

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