Alkenes oxycarbonylation

From Alkenes to Alkynes Bismuth-Catalyzed Carbo-oxycarbonylations. 137... 

An Nitrone lassen sich Alkene 1,3-dipolar addieren. Dies nutzt eine asymmetrische Syn-these von L-5-Oxa-prolin aus. Das Nitron aus 2,3 5,6-Di-0-isopropyliden-mannose-oxim mit Glyoxylsaure-tert.-butylester in situ) cyclisiert mit Ethen, wobei das (JS)-Dihstereo-mer spontan kristallisiert (3R)- bzw. (3S)-3-tert.-Butyloxycarbonyl-2-(2,3 5,6-di-0-iso-propyliden-ct-D-mannofuranosyl) l,2-oxazolidin[9i%, 54% de (S43%].Nachder Abspaltung des Aldose-Restes erhalt man (S)-5-Oxa-prolin-tert.-butylester (3-tert.-Butyl-oxycarbonyl-1,2-oxazolidin 90% Schmp. 52-530)4 ... 

The oxycarbonylation of propene under the same conditions results in the formation of crotonic acid as the major product instead of the more valuable methacrylic acid.439 When the oxycarbonylation of ethylene or terminal alkenes is carried out in anhydrous alcoholic solvents instead of acetic acid, dialkyl succinates and /3-alkoxy esters are the major products (equation 173).441,442... 

Finally, Section 4.7.3. deals with two less familiar, alternative methods for the construction of the /5-oxycarbonyl moiety already mentioned above. These are the addition of an acyl cation/O-anion to a C-C double bond (Section 4.7.3.1.), and the epoxidation of an EWG-sub-stituted alkene followed by regioselcctive reductive opening of the epoxide ring (Section 4.7.3.2.). 

Whether a cyclopropanation reaction is stereospecific or not, is often tested with (Z)- and ( )-but-2-ene, but of course, this problem also holds for other diastereomeric alkenes. The following carbenes, generated by direct irradiation of the corresponding a-diazocarbonyl compound, undergo stereospecific or highly stereoselective cycloaddition to (Z)- and ( )-but-2-ene methoxycarbonylcarbene, chloro-, bromo- and iodo(ethoxycarbonyl)carbene, ° eth-oxycarbonyl(trimethylsilyl)carbene, ethoxycarbonyl(trimethylgermyl)carbene, ethoxy-... 

UV Irradiation of an 3-aryl-2-azidoacrylic ester (2-azidocinnamate) results in elimination of nitrogen and formation of a 2/f-azirine, which undergoes spontaneous electrocyclic ring opening to give a reactive intermediate which can react as an azomethine ylide dipole or an alk-oxycarbonyl(benzylidenimino)carbene. In favorable cases, the carbene form can be trapped by intramolecular [l-t-2] cycloaddition to an alkene double bond to give a dihydro-cyclopropa[c]isoquinoline, e.g.l, and 2 (Houben-Weyl, Vol. E19b, pi 166). 

Both singlet and triplet photosensitization of (Z)-cyclooctene (50) produces the (E)-cyclooctene enantiomers [(—)-(/ )-51 and ( I )-(.S )-51 Scheme 6.14]. High enantio-differentiation (Special Topic 6.1) has been achieved with singlet excited chiral polyalkyl benzenepolycarboxylates, whereas triplet sensitization (e.g. with chiral alkyl benzyl ethers) gives low optical yields only. For example, when a chiral tetra[(—)-bomyl]oxycarbonyl singlet sensitizer 52 was used at —88 °C, ( )-(R)-5 was obtained in 9% chemical yield and 41% optical purity at 12% conversion. The effect is attributed to specific interactions within an exciplex formed between sensitizer and alkene. 

In the case of electron-poor cycloalkenes, there is no regiochemical uncertainty since the cycloaddition exclusively affords the 4-oxycarbonyl or the 4-substituted carbonyl-4,5-dihy-droisoxazole93-95,171-173. Stereocontrol ranges from good (d.r. 89 11) to complete (a single isomer produced), independent of alkene ring size. 

Consiglio and colleagues described the enantioselective version of bis-alk-oxycarbonylations of alkenes [25-27], Here, BQ was applied to reoxidize the palladium centre. As chiral ligands, DIOP, BINAP, and some other chiral phosphine ligands were tested. More recently, Chan s group succeeded in using modified dipyridylphosphine cationic Pd(II) complexes to obtain both good ee and chemoselectivity. ... 

It should finally be mentioned that the nucleophilic group in Pd-catalyzed tandem reactions based on oxycarbonylation can also be a carboxyl function. " Some convincing examples were reported by Yoshida, Tamaru, and co-workers who used this reaction for the stereoselective synthesis of bislactones (Table 6). Following the mechanistic pattern shown in Scheme 14 the carboxyl group at first attacks the alkene. The intermediate Pd-acyl species then reacts with the hydroxy function to give a m-fused bislactone. A substituent in 2-position increases the reactivity however, substituents at the double bond have no significant influence on the reaction. 

The dimethylsulphide adduct of thexylchloroborane reduces aliphatic carboxylic acids to aldehydes in 93-99% yields at 25 C. Investigations of the relative merits of dimethyl and diphenyl-bromoborane as reagents lor the cleavage of acetals and ketals have been reported as has a new method for the regioselective introduction of the oxycarbonyl or thioacetal functionalities into alkenes. ... 

Recent work on crystallinity measurements is reported below sulfur containing ether ketones [14], polyethylene glycol [15], polystyrene (PS) [16, 17], (PC) [18], polyphenylene alkene diyls [19, 20], isotactic polypropylene [20, 21], polyethylene [21, 22], polyimide [23], poly(2,5 bis (4-methoxyphenyl) oxycarbonyl styrene [24], polyazomethine esters [25], PET-polybutylene terephthalate blends [26], polycyclohexyl ethylene copolymers [27], polycaprolactone [28], syndiotactic polystyrene [29, 30], polyvinylidene fluoride-trifluorethylene copolymer [30], polyethers [31], isotactic methyl methacrylate [32], soy protein isolate polymers [33], polyamide 6/66 [34], polytrimethylene-2,6-naphthalate [35, 36], PE like polyesters [37], polycyclohexadiene [38], p-dioxolone, L-lactide - polyethylene glycol copolymers [39], ethylene - methacrylic acid copolymers and ionomers [40]. 

A route to 3,5-anhydro-2-deoxy-l,4-glyconolactones by Pd(II)-catalysed oxycarbonylation is illustrated by the case of the alkene (15) derived from D-mannitol (Scheme 2). 7 C/i -alkenes such as (16) can be obtained from 5-aIdehydo-ptniosc derivatives by application of Wittig reactions in methanol. When treated with acidic methanol, (16) gives the 3,6-anhydro-2-deoxyheptonolactone derivative (17), with the proposed intermediate being shown (Scheme 3) three other similar cases were reported. 8... 

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 ... 

Kapitan P, Gracza T. Asymmetric intramolecular Pd(II)-catalysed oxycarbonylation of alkene-l,3-diols. ARKIVOC 2008 viii 8-17. 

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