Acids olefin carbonylation

Additions include the attachment of two univalent atoms or groups (called addends) to an unsaturated system, e. g., to olefins, carbonyl groups, aromatic systems, carbenes, etc. (Rule 2.1). For example, the addition of hydrocyanic acid to the car-... 

An excellent review of the problems of the enantioselective heterocatalytic hydrogenation of prochiral double bonds, covering the literature up to 1970, has been compiled by Izumi57). Raney nickel catalysts modified with chiral amino acids or dipeptides gave only very moderate enantiomeric excesses of between 0 and 10% in the hydrogenation of olefins, carbonyl compounds or oximes 57). Only Raney nickel modified with (S)-tyrosine furnished a higher enantiomeric excess in the products58). 

On the pages which follow, general methods are illustrated for the synthesis of a wide variety of classes of organic compounds including acyl isocyanates (from amides and oxalyl chloride p. 16), epoxides (from reductive coupling of aromatic aldehydes by hexamethylphosphorous triamide p. 31), a-fluoro acids (from 1-alkenes p. 37), 0-lactams (from olefins and chlorosulfonyl isocyanate p. 51), 1 y3,5-triketones (from dianions of 1,3-diketones and esters p. 57), sulfinate esters (from disulfides, alcohols, and lead tetraacetate p. 62), carboxylic acids (from carbonylation of alcohols or olefins via carbonium-ion intermediates p. 72), sulfoxides (from sulfides and sodium periodate p. 78), carbazoles... 

Acid chloride—olefin addition and Friedel-Crafts cyclization A previous procedure was improved by use of methylene chloride as solvent rather than carbon disulfide. To check the progress of the reaction, one can quench a 2 3-ml. aliquot with water in a test tube, separate and dry the organic phase, and evaporate. The infrared spectrum will show disappearance of the acid chloride carbonyl band at 5.6(1 /j and appearance of the... 

The absolute stereochemical selectivities achieved in these reactions can be explained in terms of the nnf/-exo-transition-state models 16, 17, and 18, which are analogous to those previously proposed for the reaction of dienes and olefinic dienophiles (Fig. 8) [12,27d]. These transition-state models are based on three assumptions (i) the substituent in the chiral ligand blocks the same enantiofacial side of the carbonyl in the Diels-Alder reactions of acetylenic and olefinic aldehydes (ii) exo-transition structures predominate and (hi) anh-coordination of the bulky chiral Lewis acid to carbonyl is preferred in the transition state. 

The production of carboxylic acids other than propionic acid by carbonylation is of little industrial relevance today. In principle the same catalytic systems that can be used for the carbonylation of ethylene (or any other adequate equivalent) to propionic acid are applicable for the synthesis of the higher carboxylic acids from olefins [32]. 

Rhenium catalysts. H. Smith Broadbent and co-workers have reported the preparation of a number of oxides of rhenium (RcbOt. ReOj, ReOa, ReO), which are effective hydrogenation catalysts, particularly for the reduction of carboxylic acids to primary alcohols. Kor the reduction of aromatic, olefinic. carbonyl, and nitro groups they are less aclivc than nickel or plutimim calalysts hence selective hydrogenation is possible. Bcn/ylic hydroxyl groups are stable to hydrogenolysis. 

Carbonylation of olefins in the presence of alcohols to give esters is called hydroesterification. Similarly, olefin carbonylation in the presence of carboxylic acids yields acid anhydrides. Both hydroesterification and acid anhydride formation by olefin carbonylation are covered in section 14.6.4. Other carbonylation variations, including the use of acetylenic substrates, thiols and amines as hydrogen sources and the carbonylation of allylic halides are not discussed. Several excellent reviews of hydrocarboxyiation and carbonylation of olefinshave appeared. 

As with Co, Rh and Ir catalyze the olefin carbonylation reactions of hydrocarboxylation, hydroesterification and acid anhydride formation. Rhodium or Ir complexes and iodide promoters with HjO as the hydrogen source yields a mixture of linear and branched carbocylic acids the branched isomer predominates. Many soluble complexes, such as Irlj, Ir2(CO)4Br2, Rh(PPh3)2(CO)Cl or Ir[(C4H9)3P](CO)I can be utilized as a solution in a carboxylic acid solvent. The iodide source can be HI or any material which... 

Ester synthesis by olefin carbonylation has been known for three decades. For example, Pd(II) chloride in ethanol containing 15% HCl at 80°C and 10 MPa, slowly converts a mixture of CO and ethylene to ethyl propionate. The by-products, obtained in small amounts, are ethyl j8-ethoxypropionate and ethyl y-ketocaproate. Vinyl chloride gives ethyl propionate and ethyl chloropropionate. Terminal olefins of Cj chain length give a mixture of linear and a-methyl acid esters. 

A Ng-satd. soln. of 1-heptene, methanol, dichlorobis(triphenylarsine)-platinum(II), and SnCl2 2H20 as co-catalyst in methyl isobutyl ketone deoxygenated with a N2"purge in an autoclave, and heated 3-6 hrs. at 80° under 200 atm. CO methyl octanoate. Y 92%. F. e. and catalysts s. J. F. Knifton, I. Org. Chem. 41, 793 (1976) with Pd- instead of Pt-complex catalysts cf. ibid. 41, 2885 olefin carbonylation with PdCl2/CuCl2, also formation of alkoxycarboxylic and di-carboxylic acid esters, s. D. E. James, L. F. Hines, and J. K. Stille, Am. Soc. 98, 1806,1810 (1976). 

However, the reaction proceeded only under drastic conditions (pressure 700 upward to 900 atm) in the presence of mineral acids, BFg or metal halogenides. At that time metal carbonyls had been regarded as catalyst poisons. However, Reppe could prove that olefins react with carbon monoxide and water in the presence of metal carbonyls. The reaction products are saturated carboxylic acids. Whereas Ni(CO)4 is the preferred catalyst in the carbonylation of acetylenes, cobalt, rhodium and ruthenium catalysts are equivalent or superior in olefin carbonylation. Also palladium and hydrochloric acid containing catalyst systems are of special activity in hydrocarboxylation [469-471]. Iron has an accelerating effect [472]. Addition of boric acid to Ni or Co catalysts increases the catalyst life and suppresses the formation of insoluble polymer products [473]. 

The presence of the silyl substituent at the olefinic carbon provides an important featnre in the regio- and stereochemical control of the Lewis acid-catalyzed carbonyl-ene reactions which gives 230 (equation 188). The changeover of the olefinic stereoselectivity from trans to cis is observed (c/231a) (eqnation 189). when R is a silyl gronp ". Withont a silyl group (R = H) trans product 231b is obtained predominantly. It is noteworthy... 

Carbonyl ene reactions normally require the assistance of a Lewis acid to activate the carbonyl group [126]. Such reactions are useful for creating five- and six-membered rings from acyclic olefin carbonyl precursors. The configuration of on-ring stereocenters can be efficiently controlled by the reaction conditions. 

The palladium(II)-catalyzed olefin carbonylation reaction was first reported more than 30 years ago in studies by Stille and co-workers and James et al. The reaction of carbon monoxide with cis- and tra 5-but-2-ene in methanol in the presence of palladium(II)-chloride and copper(II)-chloride yielded threo- and eryt/zro-3-methoxy-2-methyl-butanoate, respectively. The transformation that was based on the well-known Wacker process for oxidation of ethylene into acetaldehyde in water " is now broadly defined as the Pd(II)-catalyzed oxycarbonylation of the unsaturated carbon-carbon bonds. This domino reaction includes oxypalladation of alkenes, migratory insertion of carbon monoxide, and alkoxylation. Since the development of this process, several transformations mediated by palladium(II) compounds have been described. The direct oxidative bisfunctionalization of alkenes represents a powerful transformation in the field of chemical synthesis. Palladium(II)-promoted carbonylation of alkenes in the presence of water/alcohol may lead to alkyl carboxylic acids (hydrocarboxylation), diesters [bis(aIkoxycarbonyla-tion)], (3-alkoxy carboxylic acids (alkoxy-carboxylation), or (3-alkoxy esters (alkoxy-carbonylation or alkoxy-alkoxy-carbonylation). Particularly attractive features of these multitransformation processes include the following ... 

The Lewis-acid-catalyzed carbonyl-ene reaction represents an important alternative method for the addition of an allyl group to a carbonyl group (Equation 23). The resulting secondary homoallylic alcohols are amenable to a number of structural modifications and constitute useful synthetic building blocks. Because the olefin of the products can be a surrogate for a carbonyl functionality, these homoallylic alcohol are formally the synthetic equivalent of aldol addition products. Powerful asymmetric versions of the carbonyl-ene reaction [196, 197] provide an important alternative to the more traditional allylation methods, which primarily employ silanes, boranes, or stannanes (see Chapter 5). 

Later examples of the olefination of carbonyl compounds, which are extremely sensitive towards acid or basc catalyzed rearrangements, have been given by G. Buchi and by R.B. Woodward. 

The following acid-catalyzed cyclizations leading to steroid hormone precursors exemplify some important facts an acetylenic bond is less nucleophilic than an olelinic bond acetylenic bonds tend to form cyclopentane rather than cyclohexane derivatives, if there is a choice in proton-catalyzed olefin cyclizations the thermodynamically most stable Irons connection of cyclohexane rings is obtained selectively electroneutral nucleophilic agents such as ethylene carbonate can be used to terminate the cationic cyclization process forming stable enol derivatives which can be hydrolyzed to carbonyl compounds without this nucleophile and with trifluoroacetic acid the corresponding enol ester may be obtained (M.B. Gravestock, 1978, A,B P.E. Peterson, 1969). 

The addition of alcohols to form the 3-alkoxypropionates is readily carried out with strongly basic catalyst (25). If the alcohol groups are different, ester interchange gives a mixture of products. Anionic polymerization to oligomeric acrylate esters can be obtained with appropriate control of reaction conditions. The 3-aIkoxypropionates can be cleaved in the presence of acid catalysts to generate acrylates (26). Development of transition-metal catalysts for carbonylation of olefins provides routes to both 3-aIkoxypropionates and 3-acryl-oxypropionates (27,28). Hence these are potential intermediates to acrylates from ethylene and carbon monoxide. 

Oxidative Carbonylation of Ethylene—Elimination of Alcohol from p-Alkoxypropionates. Spectacular progress in the 1970s led to the rapid development of organotransition-metal chemistry, particularly to catalyze olefin reactions (93,94). A number of patents have been issued (28,95—97) for the oxidative carbonylation of ethylene to provide acryUc acid and esters. The procedure is based on the palladium catalyzed carbonylation of ethylene in the Hquid phase at temperatures of 50—200°C. Esters are formed when alcohols are included. Anhydrous conditions are desirable to minimize the formation of by-products including acetaldehyde and carbon dioxide (see Acetaldehyde). 

In a polluted or urban atmosphere, O formation by the CH oxidation mechanism is overshadowed by the oxidation of other VOCs. Seed OH can be produced from reactions 4 and 5, but the photodisassociation of carbonyls and nitrous acid [7782-77-6] HNO2, (formed from the reaction of OH + NO and other reactions) are also important sources of OH ia polluted environments. An imperfect, but useful, measure of the rate of O formation by VOC oxidation is the rate of the initial OH-VOC reaction, shown ia Table 4 relative to the OH-CH rate for some commonly occurring VOCs. Also given are the median VOC concentrations. Shown for comparison are the relative reaction rates for two VOC species that are emitted by vegetation isoprene and a-piuene. In general, internally bonded olefins are the most reactive, followed ia decreasiag order by terminally bonded olefins, multi alkyl aromatics, monoalkyl aromatics, C and higher paraffins, C2—C paraffins, benzene, acetylene, and ethane. 

Olefins are carbonylated in concentrated sulfuric acid at moderate temperatures (0—40°C) and low pressures with formic acid, which serves as the source of carbon monoxide (Koch-Haaf reaction) (187). Liquid hydrogen fluoride, preferably in the presence of boron trifluoride, is an equally good catalyst and solvent system (see Carboxylic acids). 

Simple olefins do not usually add well to ketenes except to ketoketenes and halogenated ketenes. Mild Lewis acids as well as bases often increase the rate of the cyclo addition. The cycloaddition of ketenes to acetylenes yields cyclobutenones. The cycloaddition of ketenes to aldehydes and ketones yields oxetanones. The reaction can also be base-cataly2ed if the reactant contains electron-poor carbonyl bonds. Optically active bases lead to chiral lactones (41—43). The dimerization of the ketene itself is the main competing reaction. This process precludes the parent compound ketene from many [2 + 2] cyclo additions. Intramolecular cycloaddition reactions of ketenes are known and have been reviewed (7). 

These reversible reactions are cataly2ed by bases or acids, such as 2iac chloride and aluminum isopropoxide, or by anion-exchange resias. Ultrasonic vibrations improve the reaction rate and yield. Reaction of aromatic aldehydes or ketones with nitroparaffins yields either the nitro alcohol or the nitro olefin, depending on the catalyst. Conjugated unsaturated aldehydes or ketones and nitroparaffins (Michael addition) yield nitro-substituted carbonyl compounds rather than nitro alcohols. Condensation with keto esters gives the substituted nitro alcohols (37) keto aldehydes react preferentially at the aldehyde function. 

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