Lactones palladium® chloride

When either an alcohol or an amine function is present in the alkene, the possibility for lactone or lactam formation exists. Cobalt or rhodium catalysts convert 2,2-dimethyl-3-buten-l-ol to 2,3,3-trimethyl- y-butyrolactone, with minor amounts of the 8-lactone being formed (equation 51).2 In this case, isomerization of the double bond is not possible. The reaction of allyl alcohols catalyzed by cobalt or rhodium is carried out under reaction conditions that are severe, so isomerization to propanal occurs rapidly. Running the reaction in acetonitrile provides a 60% yield of lactone, while a rhodium carbonyl catalyst in the presence of an amine gives butane-1,4-diol in 60-70% (equation 52).8 A mild method of converting allyl and homoallyl alcohols to lactones utilizes the palladium chloride/copper chloride catalyst system (Table 6).79,82 83... 

In combination with the incremental advances concerning reaction conditions in recent years, especially for low-pressure carbonylations, there is a trend toward increasing use of this chemistry to synthesize advanced building blocks. In this respect carboxylation of alkenes with an appropriate alcohol or amine function leads to the formation of lactones or lactams. Thus, cobalt, rhodium, or palladium chloride/copper chloride catalysts convert allyl and homoallyl alcohols or amines to the corresponding butyrolactones or butyrolactams, respectively [15]. 

Borohydride-reduced palladium. Reduction of palladium chloride in methanol with sodium borohydride until evolution of a gas ceases leads to a black material, which is not particularly sensitive to air and is not pyrophoric. The material is useful for selective hydrogenations. It catalyzes rapid hydrogenation of bonds of the type C=C, N=N, and N=0, but not the type C=N and C=0. Nohydrogenolysisof nitrogen or oxygen functions is observed in alcohols, amines, amides, esters, ethers, or lactones. Epoxides are opened to alcohols very slowly. 

When sodium ethoxide is used in place of sodium hydroxide in the carbonylation reaction of benzyl halides with dicobalt octacarbonyl, ethyl esters are produced instead of the acids [15], Esters are also produced directly from iodoalkanes through their reaction with molybdenum hexacarbonyl in the presence of tetra-/i-butylammo-nium fluoride [16]. Di-iodoalkanes produce lactones [16]. The reaction can be made catalytic in the hexacarbonyl by the addition of methyl formate [16]. t-Butyl arylacetic esters are produced in moderate yield (40-60%) under phase-transfer catalytic conditions in the palladium promoted carbonylation reaction with benzyl chlorides [17]. 

The mechanism of the Zn chloride-assisted, palladium-catalyzed reaction of allyl acetate (456) with carbonyl compounds (457) has been proposed [434]. The reaction involves electroreduction of a Pd(II) complex to a Pd(0) complex, oxidative addition of the allyl acetate to the Pd(0) complex, and Zn(II)/Pd(II) transmetallation leading to an allylzinc reagent, which would react with (457) to give homoallyl alcohols (458) and (459) (Scheme 157). Substituted -lactones are electrosynthesized by the Reformatsky reaction of ketones and ethyl a-bromobutyrate, using a sacrificial Zn anode in 35 92% yield [542]. The effect of cathode materials involving Zn, C, Pt, Ni, and so on, has been investigated for the electrochemical allylation of acetone [543]. 

In several of the previously described methods the anion of the three-carbon fragments was added to an a-amino aldehyde to construct a C—C bond between the C3 and C4 atoms of the 1-hydroxyethylene isostere. However, Sakurai et al.[27l used an add chloride instead of an a-amino aldehyde. They synthesized 6-phthalimido-y-oxo esters by a palladium-catalyzed reaction between acid chlorides and organozinc reagents derived from p-iodo esters. Then, the oxo esters were converted into the y-lactone precursors. 

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... 

The same reactions, carried out with potassium carbonate as base in place of a secondary amine, yield exocyclic dienes in good yield, although double-bond isomerization sometimes occurs (equation 38).93 Inclusion of tetra-zi-butylammonium chloride in the reaction mixture stops the double-bond isomerization. Thus, the reaction in equation (38) with the chloride yields only the bis(exomethylene) product in 45% yield in a slow reaction. Some N- and O-heterocyclic products, also, have been prepared by the intramolecular vinyl substitution reaction.94 A 16-membered ring lactone was made by the ring closure of a vinylic iodide group with a vinyl ketone group. The yield, based upon the reactant, was 55% but a stoichiometric amount of bis(acetonitrile)palladium dichloride was employed. The catalyst was prereduced with formic acid so that the reaction proceeded at 25 C (equation 39).95... 

The carbanion is trapped with iodine to give 42. which makes a further functionali/aiion possible. Conversion of vinylic iodide 42 into a lactone is accomplished by palladium-cataly/ed carbonyla-tion under Stille conditions.13 This process ean be broken down into the following elementary reactions a) Oxidative addition of Pd° to vinylic iodide 42 with formation of 43 b) An insertion reaction of carbon monoxide with creation of the pallada-acyl species 44 c) Reaction of acid-chloride equivalent 44 with the alcohol to give lactone 13. 

With catalytic amounts of palladium(II) chloride with copper(II) chloride as oxidant, the yields of the lactones were reduced to half of the yields obtained with stoichiometric amounts of palladium(II) chloride1. 

While the condensation of enamine 37 with methyl OY7 s-2-butenoate, followed by acid hydrolysis and sodium borohydride reduction affords lactone 38 with reasonable efficiency, the cyclodehydrative ring contraction of this intermediate with PPA gives a mixture of bicyclo[3.3.0]octenones in abysmal (< 5 %) yield.66 To circumvent this difficulty and enable the large scale production of 39,2-carbo-methoxy-4,4-dimethylcyclohexanone was initially transformed to tram diacid 40 under Favoiskii conditions (Scheme 14). Conversion to the diacid chloride and condensation with lithium dimethylcuprate resulted in formation of the diacetyl derivative. In basic solution, the latter is reported to experience epimerization and aldol cyclization with dehydration in 82 % yield. With hydrogen and palladium on charcoal, the essentially quantitative production of 39 was achieved.66 ... 

LACTONES Dichlorobisicyclopenta-dienylltitanium. Ferric chloride. Pal-ladium(O) complexes. N-Phenylseleno-phthalimide. N-Phenylselenosucdnimide. Tetrakis(triphenylphosphine)palladium-(0). (3-Vinylbutenolide. See also LAC-TONIZATION. 

A useful extension of the alkoxycarbonylation reaction has been devised in order to obtain 3,4-dihydro-4-hydroxy-l//-2-benzopyran-3-acetic acid lactones from 5-alkene-l,4-diols. The intramolecular cyclization of 7, carried out with palladium(II) acetate and copper(II) chloride under a carbon monoxide atmosphere, affords the m-lactone 8 in 68% yield. The configuration is assigned on the basis of H-NMR double resonance methods86. 

The dihydroxy lactone from L-threonic acid is prepared from L-dibenzoyl tartaric anhydride by catalytic hydrogenation over palladium. The substituted anhydride is formed from tartaric acid and benzoyl chloride. 

Copper(I) triflate was used as a co-catalyst in a palladium-catalyzed carbonylation reaction (Sch. 27). The copper Lewis acid was required for the transformation of homoallylic alcohol 118 to lactone 119. It was suggested that the CuOTf removes chloride from the organopalladium intermediate to effect olefin complexation and subsequent migratory insertion [60]. Copper(I) and copper(II) chlorides activate ruthenium alkylidene complexes for olefin metathesis by facilitating decomplexation of phosphines from the transition metal [61]. 

Allene carboxylic acids have been cyclized to butenolides with copper(II) chloride. Allene esters were converted to butenolides by treatment with acetic acid and LiBr. Cyclic carbonates can be prepared from allene alcohols using carbon dioxide and a palladium catalyst, and the reaction was accompanied by ary-lation when iodobenzene was added. Diene carboxylic acids have been cyclized using acetic acid and a palladium catalyst to form lactones that have an allylic acetate elsewhere in the molecule. With ketenes, carboxylic acids give anhydrides and acetic anhydride is prepared industrially in this manner [CH2=C=0 + MeC02H (MeC=0)20]. 

The addition of sodium benzenetellurolate to 3-hydroxy-1-propynes produces (Z)-2-hydroxyalkylethenyl phenyl telluriums. These compounds treated with carbon monoxide in dichloromethane in the presence of stoichiometric amounts of triethylamine and palladium(II) chloride are carbonylated and the resulting acids converted to lactones. ... 

P-Lactones can be obtained by oxidative carbonylation of alkenes in the presence of water. Ethylene, for example, is converted to p-propiolactone by carbonylation in aqueous acetonitrile at -20 C using a catalytic amount of PdCh and a stoichiometric quantity of copper(II) chloride (equation 37). Palladium-catalyzed carbonylation of halides can also be used to prepare p-lactones under mild conditions. The reaction takes place at room temperature and pressure in the presence of [PdCl2(PPh3)2] and has been applied to both bromides and chlorides (equations 38 and 39). 

Addition of dichloroketen to cyclohexenyl phenyl sulphoxide yields the ds-lactone (18). The methylbutanolide (19) is formed by the reaction of but-3-en-l-ol with carbon monoxide in the presence of palladium(II) chloride, copper(II) chloride, and triphenylphosphine. Palladium(0)-phosphine complexes catalyse the carboxylation of isopropylidenecyclopropane to give the furanone (20). ... 

Carbonylation of o-allylbenzyl halides.1 Carbonylation (600 psi) of o-allylbenzyl chloride (1) in the presence of triethylamine (2 equiv.) and in the presence of this palladium catalyst (5 mol %) provides the benzoannclatcd cnol lactone (2) in 78% yield. 

The projected palladium-catalyzed cross-coupling required the availability of vinylstannane 216. As shown in Scheme XXV, the preparation of this lactone was initiated by copper-catalyzed 1,4-addition of l-(trimethylsilyl)vinylmagne-sium bromide to 5(2//)-furanone (212). For this process to be successful, excess trimethylsilyl chloride had to be present from the outset in order to trap the enolate as it was formed and circumvent its polymerization. This modification gave rise to C-silylated lactone 213, which was chemoselectively desilylated and transformed via vinyl bromide 215 [120] into stannane 216. 

Palladium(Il) chloride-copperfll) chloride-oxygen. 18,283 19,261-262 20,294 Oxidation. As an extension of the lactone synthesis from 1-trimethylsilyl-... 

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