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... 

Bisdecarboxylation of vicinal dicarboxylates is the older method of converting vicinal diacids into olefins. The reaction can be combined with a[4 + 2]- or [2 -f 2]-... 

However, the inhibition of the reaction by lithium perchlorate, that strongly favors the cationic pathway (see chap. 2, 7), contradicts this assumption. With regard to yield and the degree of passivation the decarboxylation/desilylation appears to be a better choice than the bisdecarboxylation for the construction of unsaturated polycyclic compounds (see for example Table 11, No. 12b and No. 22). 

In the bisdecarboxylation of the cyclobutenedicarboxylic acid 52, products are obtained whose formation possibly involves a cyclobutadiene intermediate [322], A case of a 1,3-bisdecarboxylation has been reported in the preparation of a bicyclobutane (Table 11, No. 26). An elimination, that involves the cleavage of an carbon-oxygen bond after the decarboxylation, has been observed with the carboxylic acid 53 (Eq. 33) [282]. 

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-... 

Compounds containing carboxyl groups on adjacent carbons (succinic acid derivatives) can be bisdecarboxylated with lead tetraacetate in the presence of O2 263 jjjg reaction is of wide scope. The elimination is stereoselective, but not stereospecific (both meso- and dl- 2,3-diphenylsuccinic acid gave trans- stilbene) a concerted mechanism is thus unlikely. The following mechanism is not inconsistent with the data ... 

Compounds containing geminal carboxyl groups (disubstituted malonic acid derivatives) can also be bisdecarboxylated with lead tetraacetate, gcm-diacetates (acylals) being produced, which are easily hydrolyzable to ketones ... 

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

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. 

Succinic acids undergo bisdecarboxylation on exposure to lead tetraacetate [264], Contra-polarization at one of the a-carbons through fragmentation of the lead(IV) carboxylate moiety enables a smooth decarboxylation of the remaining functionality. 

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... 

Allylic carboxylation. Diethyl oxomalonate (1) undergoes a thermal ene reaction with mono-, di-, and trisubstituted alkenes at 145 180°. The reaction is also subject to catalysis with Lewis acids, which can lead to a different ene product. The products are a-hydroxymalonic esters. The corresponding malonic acids are converted to carboxylic acids by bisdecarboxylation with NaI04 and a trace of pyridine- or with ceric ammonium nitrate (CAN). Diethyl oxomalonate then functions as an cnophilic equivalent of C02. 

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. 

Anodic bisdecarboxylation is normally conducted at a platinum anode in water-pyridine-triethylamine as electrolyte and with both carboxyl groups neutralized. Synthetic applications of this method are illustrated by the following examples (Eq. (139-145)). 

A two step process involving an intermediate radical or carbonium ion has been suggested as mechanism because of the fact that both meso- and d,7-2,3 -di-phenylsuccinic acid yield 35-40% trans-stilbene 314 A cationic intermediate however seems improbable for the bisdecarboxylations of aliphatic bicyclic carboxylic acids (Eq. (139-144) ), since no products with reananged carbon skeleton, as expected from carbonium ions, have been isolated. 

Anodic and cathodic elimination is simply the reverse of cathodic [eqn (16)] and anodic [eqn (15)] addition, respectively. Important cases are anodic bisdecarboxylation, either in the 1,2- (Corey and Casanova, 1963 Radlick et al., 1968 Westberg and Dauben, 1968) or 1,3-fashion (Vellturo and Griffin, 1966), with the preparation of Dewar benzene and dimethyl bicyclobutane-2,4-dicarboxylate as the more prominent cases [eqns (25) and (26)], and cathodic dehalo-genation of dihalides with the halogens in the 1,2- (Zavada et al., 1963), 1,3- (Casanova, 1974 Gerdil, 1970 Rifi, 1967, 1969), 1,4-(Casanova and Rogers, 1974 Wiberg et al., 1974) and 1,6- (Covitz, 1967) positions. The synthesis of bicyclobutanes (27) and [2,2,2]propellane (28) bear witness to the usefulness of this reaction type. 

A recent paper describes further conversion of (60). The corresponding keto-tricarboxylic acid was converted to the monoester and this was bisdecarboxylated to the diene (62). Catalytic reduction and formation of the heterocyclic ring by the well-known acyl azide photolysis gave ketolactam (63). This was transformed into the enantiomer of the known degradation product (64). 

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... 

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