Alkoxycarbonylation metals

An efficient one-pot synthesis of mikanecic acid derivatives was accomplished from allylic phosphonates, ClC02Et, and aqueous HCHO (Eq. 12.38).100 The overall process involves a cascade sequence linking together metalation-alkoxycarbonylation, Homer-Wadsworth-Emmons,... 

Hydroxycarbonylation and alkoxycarbonylation of alkenes catalyzed by metal catalyst have been studied for the synthesis of acids, esters, and related derivatives. Palladium systems in particular have been popular and their use in hydroxycarbonylation and alkoxycarbonylation reactions has been reviewed.625,626 The catalysts were mainly designed for the carbonylation of alkenes in the presence of alcohols in order to prepare carboxylic esters, but they also work well for synthesizing carboxylic acids or anhydrides.137 627 They have also been used as catalysts in many other carbonyl-based processes that are of interest to industry. The hydroxycarbonylation of butadiene, the dicarboxylation of alkenes, the carbonylation of alkenes, the carbonylation of benzyl- and aryl-halide compounds, and oxidative carbonylations have been reviewed.6 8 The Pd-catalyzed hydroxycarbonylation of alkenes has attracted considerable interest in recent years as a way of obtaining carboxylic acids. In general, in acidic media, palladium salts in the presence of mono- or bidentate phosphines afford a mixture of linear and branched acids (see Scheme 9). 

Most researchers currently agree that the hydrido mechanism is more common than the alkoxycarbonyl path in the alkoxycarbonylation of alkenes with palladium systems. However, carbalkoxy complexes are putative intermediates in carbonylation reactions giving succinates and polyketone diesters, with metals like Co, Rh, or Pd.137... 

When Wacker-type reactions are performed under a CO atmosphere, the (3-H elimination pathway can be suppressed in favor of CO insertion and subsequent nucleophilic cleavage of the acyl metal species.399 This alkoxycarbonylation process has found widespread utility, particularly in the synthesis of five- and six-membered oxacyclic natural products. For example, the THF core of tetronomycin was prepared by the Pd-catalyzed alkoxycarbonylation of 4-alkenol derivatives (Equations (117) and (118)), where stereocontrol was achieved by utilizing either the directing ability of a free hydroxyl or the conformational bias imposed by a bulky silyl ether.420 Additional examples making... 

Abstract Development in the field of transition metal-catalyzed carbonylation of epoxides is reviewed. The reaction is an efficient method to synthesize a wide range of / -hydroxy carbonyl compounds such as small synthetic synthons and polymeric materials. The reaction modes featured in this chapter are ring-expansion carbonylation, alternating copolymerization, formylation, alkoxycarbonylation, and aminocarbonylation. 

The metal-promoted processes follow a general mechanistic route, involving the intermediate formation of an alkoxycarbonyl- or a carbamoyl-metal species from the reaction between MX2, CO and NuH (NuH = alcohol, phenol or amine), followed by nucleophilic attack by Nu H (Nu I I = alcohol, phenol or amine) (Scheme 26). 

Interest in the uses of HMPT has also been maintained, but a warning has been issued (by the E. I. du Pont de Nemours Company and the U.S. National Institute for Occupational Safety and Health) about its potential acute toxicity. HMPT has been used in the synthesis of 2,4-bis(dimethylamino)qui nolines,9 8 as a solvent for reactions between carbonyl compounds and sulphur," for the conversion of iV-benzylcarbox-amides into 3-phenylpropionitriles,100 in reactions between metals or organometallic compounds with a variety of organic substrates,101 and as a solvent for alkylation reactions of /J-keto-esters and related compounds in which the alkylation reaction is accompanied by de(alkoxycarbonylation) (Scheme 7).102... 

It is noteworthy that the stereospecificity observed in the thermal reaction is fully preserved under this new catalytic manifold. Furthermore, the presence of a 2-alkoxycarbonyl substituent on the allylic boronate is not necessary for the metal-promoted activation to occur (Eq. According to mechanistic... 

There are a few reports on the amination of a-metallated carbonyl compounds with 0-(arenesulfonyl)hydroxylamine-type reagents. However, in recent years there has been substantial progress in Af-(alkoxycarbonyl) 0-(arenesulfonyl)hydroxylamine [alkyl N-(arenesulfonyloxy)carbamate]-type reagents for the amination of enolates and eniminates. 

Ionic liquids serve as very useful reaction media, which can facilitate easy separation of product(s) and a catalyst after the reaction. These substitutes of organic solvents as reaction media have already been successfully applied to a variety of transition metal-catalyzed organic reactions such as Heck reaction, Suzuki cross-coupling, hydroformyla-tion, and alkoxycarbonylation. ... 

The generation and addition of acyl- and alkoxycarbonylcarbenes to alkenes is usually carried out by using the corresponding diazo derivatives under catalysis of metallic compounds. The metal-catalyzed cyclopropanation reactions with diazo compounds are described in detail by McKervey in Chapter 11, hence dealt with rather briefly in this chapter. The readers who are interested in the preparation of acyl- and alkoxycarbonyl-substi-tuted cyclopropanes are requested to refer also to Chapter 9. 

From the preceding discussion and examples it is evident that a metal hydroxycarbonyl intermediate is central to all reductions by carbon monoxide and water. Consequently it is surprising that only two reports of stable, isolated hydroxycarbonyls have appeared, in contrast to the numerous isolated complexes of analogous alkoxycarbonyls,... 

Whereas p-keu> compounds are accessible as described through metallated phosphonic acid esters (the Co try-Kwh u low ski reaction), P-alkoxycarbonyl compounds 40 as starting materials for the Hor-ner-Wiulwsorth-Emmtms reaction are obtained via the Arbusox reaction, an Sn2 process involving phosphorus nucleophiles. 

In connection with these catalytic cyclopropanation reactions, it should be mentioned that the isolable ruthenium-carbene complex 162, which is obtained from 19, [RuCMp-cymene)]2 and 2,6-bis(4-isopropyl-l,3-oxazolin-2-yl)pyridine, reacts with styrene at elevated temperature in a carbene transfer reaction83 (equation 41). Since complex 162 is also catalytically active for (alkoxycarbonyl)carbene transfer to olefins, this reaction represents one of the few connecting links between catalytic and stoichiometric carbene transfer reactions of metal-carbene complexes. 

In a bifunctional compound, if a reagent reacts with one functional group preferentially, even though the other is apparently susceptible to the reaction conditions, the reaction is said to be chemoselective. Two illustrative examples are the reduction of a carbonyl group in the presence of a cyano, nitro or alkoxycarbonyl group (Section 5.4.1, p. 519 see also Metal hydrides, Section 4.2.49, p. 445) and the acylation of an aromatic amino group in the presence of a phenolic group (Section 6.9.3, p. 984). 

One of the uses of these ester-acyl chlorides is for the synthesis of co-hydroxy esters which involves the selective reduction of the acyl chloride grouping with sodium borohydride161 the alkoxycarbonyl group is unaffected by this metal hydride reducing agent (cf. Section 5.4.1, p. 519). 

Dibromoselenuranes, preparation, 9, 485 Dibromothiophene, alkoxycarbonyl-substituted, crosscoupling polymerization, 11, 659 Di-/< r/-butylbenzens, metallation, 9, 15—16... 

The fact that with (Z)-2-butene opposite prevailing chiralities are obtained in hydroformylation, using Rh/(—)-DIOP or Pt/(—)-DIOP catalytic systems, or in hydro-alkoxycarbonylation, using the Pd/( )-DIOP catalytic system, can be explained according to the model assuming that the metal atoms have opposite chiralities in the two cases. 

Carbamoyl or alkoxycarbonyl complexes 87 are obtained by the attack of amines or alkoxides to metal carbonyls. They are important intermediates of carbonylation reactions and undergo insertion of alkene and alkyne. 

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