Carbon dioxide reactions with dienes

The reaction of CO2 with complexes containing M —N bonds may proceed according to the mechanisms (13.236) and (13.237). Carbon dioxide reacts with 1,3-dienes,... 

Carbon dioxide reacts with 1-hexyne to give 4,6-dibutyl-2-pyrone in addition to tributylbenzenes " [equation (13.239)]. A stoichiometric reaction of dienes with CO2... 

These polymers are sensitive to thermolysis and decomposes rapidly and smoothly to bisphenol A, carbon dioxide, and volatile dienes when heated near 200 . For example polymer 8 affords only benzene, carbon dioxide, and bisphenol A upon heating. As in the case with t-butyl esters and carbonates, this thermolysis reaction is susceptible to acid catalysis and this property forms the basis of our resist design. The tertiary polycarbonate resist is formulated by casting a polymer film from a solution containing a few percent of substances which will produce strong acid upon photolysis. 

The Nobel Laureates involved in cycloaddition chemistry include Sharpless (2001), Staudinger (1953), Diels and Alder (1950) and Wittig (1979) and today s emphasis on green chemistry has accelerated research in this field. For example, cycloaddition reactions of carbon dioxide could be of interest for sequestering of greenhouse gases. In addition, sulfur dioxide readily undergoes cycloaddition reactions with dienes. 

Carbon dioxide instead of aldehydes can be involved in Ni(0)-promoted reductive coupling reactions (Equations (76) and (77) Scheme 90).434,434a 434c A stoichiometric amount of Ni(COD)2/DBU reacts with C02 and dienes, alkynes, or allenes to afford a metallacycle intermediate. This metallacycle reacts with organozinc compounds or aldehydes in one-pot to give carboxylic acid derivatives. As shown in Scheme 90, double carboxylation occurs in the presence of dimethylzinc, where the stereochemical outcome is opposite to that of the reaction with diphenylzinc. 

Although numerous advantages are associated with the use of supercritical carbon dioxide (scC02) as an ecologically benign and user friendly reaction medium, systematic applications to metal-catalyzed processes are still rare. A notable exception is a recent report on the use of scC02 for the formation of industrially relevant polymers by ROMP and the eyelization of various dienes or enynes via RCM [7]. Both Schrock s molybdenum alkylidene complex 24 and the ruthe-... 

Equations 1 to 3 show some of fixation reactions of carbon dioxide. Equations la and lb present coupling reactions of CO2 with diene, triene, and alkyne affording lactone and similar molecules [2], in a process catalyzed by low valent transition metal compounds such as nickel(O) and palladium(O) complexes. Another interesting CO2 fixation reaction is copolymerization of CO2 and epoxide yielding polycarbonate (equation 2). This reaction is catalyzed by aluminum porphyrin and zinc diphenoxide [3],... 

Rigby and coworkers305,309 also performed metal mediated [6 + 4] cycloadditions of heterocyclic trienes and tropones with various dienes. In concurrence with the all-carbon trienes, the electronic nature of the diene partners generally had little influence on the cycloaddition efficiency. The only reported exceptions are the reactions of thiepin-1,1-dioxides. Lower yields were observed in the reactions involving electron-deficient dienes in comparison with the reactions with electron-rich dienes. The reaction of complex 514... 

S. Akutagawa and S. Otsuka, J. Amer. Chem. Soc., 1976, 98, 7420 the formula for isogeraniol lacks the 6,7-double bond and the diene minor product is named incorrectly. No experimental details are given for the hydrolysis of this myrcene-magnesium complex but the results contradict those reported by Cookson et al. who have extensively investigated its reactions with carbonyl compounds, epoxides, carbon dioxide, and acetonitrile. ... 

In the past, this field has been dominated by ruthenium, rhodium and iridium catalysts with extraordinary activities and furthermore superior enantioselectivities however, some investigations were carried out with iron catalysts. Early efforts were reported on the successful use of hydridocarbonyliron complexes HFcm(CO) as reducing reagent for a, P-unsaturated carbonyl compounds, dienes and C=N double bonds, albeit complexes were used in stoichiometric amounts [7]. The first catalytic approach was presented by Marko et al. on the reduction of acetone in the presence of Fe3(CO)12 or Fe(CO)5 [8]. In this reaction, the hydrogen is delivered by water under more drastic reaction conditions (100 bar, 100 °C). Addition of NEt3 as co-catalyst was necessary to obtain reasonable yields. The authors assumed a reaction of Fe(CO)5 with hydroxide ions to yield H Fe(CO)4 with liberation of carbon dioxide since basic conditions are present and exclude the formation of molecular hydrogen via the water gas shift reaction. H Fe(CO)4 is believed to be the active catalyst, which transfers the hydride to the acceptor. The catalyst presented displayed activity in the reduction of several ketones and aldehydes (Scheme 4.1) [9]. 

Pyrones behave as dienes and react with bismaleimides giving biscycload-ducts [62-65]. By heating, carbon dioxide extrusion takes place with formation of bisdienes. This reaction was used to prepare a polyimide with a bicyclooctene structure [51] (Fig. 15). 

This has been essentially accomplished in a case of the diene-dienophile monomer polymerization (6, 7, 8, 16). This excellent work makes use of the reaction of such dienes as cyclopentadienones, a-pyrones, and thiophene dioxides with dienophiles. The resulting adduct, a protected or inactive diene, loses carbon monoxide, carbon dioxide, or sulfur dioxide at elevated temperatures to form a diene. Thus when a Ws-malei-mide reacts with one mole of a cyclopentadienone, the resulting adduct will lose carbon monoxide at 150—260° in an inert solvent to form an active intermediate diene-dienophilic monomer which readily poly-... 

One remarkable group of homogeneous CO reactions 1 that of the conversions with unsaturated hydrocarbons using alkynes. alkcnes or dienes as the adducts, lactones, acids or esters are produced. The two most efficient catalyst metals are rhodium and palladium. This part of CO chemistry is a very fascinating one, because carbon dioxide is fixed in the organic compounds, through the formation of a new carbon-carbon bond. 

Dienes, especially butadiene, also react with carbon dioxide. Inotie and his co-workeis found that Pd(dppe)j catalyzes the telomerization of butadiene and CO to give the y-lactone 2 Cthylidcnc-5 hcpien-4-oUde in about a S% yield [182, 183]. The distribution of the products evidently depends on the solvent used and polar aproiic solvents such as DMF, DMSOand 1 mielhyl-2-pyrrolidone are most suitable for lactone formation. A temperature of 120 C is required. When the reaction is carried out at temperatures below lOO C and terminated before the complete conwrsion of butadiene, the free organic acids (the precursors of the >4actone) are isolated up to 10%. 

Few examples of functionalization on the benzene ring of benzisothiazole have been reported (see Section 4.05.7.2). Studies on the reactivity of unsaturated chains in cycloaddition reactions have been reported (see Section 4.05.7.3). The high reactivity of 4-vinylisothiazolin-3-one A-oxides in Diels-Alder cycloadditions, both as diene and dienophile, is illustrated by their tendency to dimerize. 5-Vinylisothiazole A,A-dioxides react at the vinyl function with different 1,3-dipoles. Isothiazolo-3-sulfolenes 265 give an o-quinodimethane which can be trapped with a dienophile. Different isothiazole derivatives substituted with a carbon chain functionalized with heteroatoms have been prepared as ligands for the formation of complexes. 3-Oxocamphorsulfonimide reacts with the anion of alkynes and several studies on the reactivity of the products with electrophiles are reported. 

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]. 

Addition of water to dienes is catalyzed by palladium complexes. The reaction has been used for synthesizing unsaturated alcohols and ethers from aliphatic conjugated C4 and Cg olefins 248). In particular, the hydration of butadiene with water in the presence of bis(2,4-pentane-dionato)palladium and triphenylphosphine gave 2,7-octadien-l-ol, l,7-octadien-3-ol, and 1,3,5,7-octatetraene 18). The reaction was accelerated by carbon dioxide. Compounds Pd(PPh3)4 and Pd(02C0)-(PPh3)2 were also effective. 

When 2 was treated with only one equivalent of acetone, no product derived from the reaction of 2 with two molecules of acetone was observed, indicating that in the presence of 2, the initially formed adduct 12 did not add competitively to the unreacted acetone. This feature allowed both acetone and, subsequently, added carbon dioxide to be delivered to the original diene at the desired positions. However, if excess acetone was used, 12 underwent further nucleophilic addition to the ketone, yielding the corresponding diol. Therefore, it was essential to not use more than 1 Eq of acetone for the synthesis of 16. 

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