Insertion of carbon monoxide into

Although analogous to the direct coupling reaction, the catalytic cycle for the carbonylative coupling reaction is distinguished by an insertion of carbon monoxide into the C-Pd bond of complex A (see A—>B, Scheme 31). The transmetalation step-then gives trans complex C which isomerizes to the cis complex D. The ketone product E is revealed after reductive elimination. 

It should be noted that, similarly to olefin, the insertion of carbon monoxide in the active bond in the propagation centers of polymerization catalysts also follows the coordination mechanism 175). The insertion of carbon monoxide into the active bond was not feasible when a vacant coordination site of the metal ion had been occupied by phosphine. 

This chapter is concerned entirely with the insertion of carbon monoxide into transition metal-carbon cr-bonds. Sulfur dioxide insertion 154, 239), also common among transition metal-carbon complexes, will be treated in a complementary review, which is to appear later. Subject to the restrictions given at the beginning of Section VI, an attempt has been made at a complete literature coverage of the insertion of CO. Particular emphasis focuses on recent results, especially those of a kinetic and stereochemical nature. 

Treatment of the olefin 49 with Zeise s dimer leads to the chloroplatination complex 50 [26], The addition adduct 50 is hydrogenated stereospecifically to the trans-disubstituted chlorocyclohexane 51. The insertion of carbon monoxide into 50, in the presence of methanol, yields the ester 52 stereoselectively. 

The insertion of carbon monoxide into readily available 2-bromo-3-aminopropene derivatives can be effected by catalytic quantities of palladium acetate and triphenylphosphine high CO pressures are not required (Scheme 16).38 The /Mactam products presumably arise by palladation,carbonylation, and cyclization as depicted in Scheme 17.38 An extension of this approach to the synthesis of biologically interesting condensed /(-lactams can be expected. 

Formation of the reduced 1,3-oxazepine derivative 160 from the reaction of diiron nonacarbonyl with the tetrahydrooxazine derivative (159) involves a novel formal insertion of carbon monoxide into an N—O bond (Scheme 183).248 The synthetic applicability of this unusual reaction has not been evaluated. 

This article reviews recent results on the chemical, spectral and structural properties of bis(pentamethylcyclopentadienyl) thorium and uranium dihaptoacyl complexes produced by migratory insertion of carbon monoxide into actinide-carbon sigma bonds. 

Carbon monoxide rapidly inserts into the carbon—zirconium bond of alkyl- and alkenyl-zirconocene chlorides at low temperature with retention of configuration at carbon to give acylzirconocene chlorides 17 (Scheme 3.5). Acylzirconocene chlorides have found utility in synthesis, as described elsewhere in this volume [17]. Lewis acid catalyzed additions to enones, aldehydes, and imines, yielding a-keto allylic alcohols, a-hydroxy ketones, and a-amino ketones, respectively [18], and palladium-catalyzed addition to alkyl/aryl halides and a,[5-ynones [19] are examples. The acyl complex 18 formed by the insertion of carbon monoxide into dialkyl, alkylaryl, or diaryl zirconocenes may rearrange to a r 2-ketone complex 19 either thermally (particularly when R1 = R2 = Ph) or on addition of a Lewis acid [5,20,21]. The rearrangement proceeds through the less stable... 

Insertion of carbon monoxide into Csp2—Zr bonds occurs readily at ambient temperatures or below to produce a,(5-unsaturated, reactive acyl zirconocene derivatives [27—29]. Early work by Schwartz demonstrated the potential of such intermediates in synthesis [5d], as they are highly susceptible to further conversions to a variety of carbonyl compounds depending upon manipulation. More recently, Huang has shown that HC1 converts 16 to an enal, that addition of a diaryl diselenide leads to selenoesters, and that exposure to a sulfenyl chloride gives thioesters (Scheme 4.11) [27,28]. All are obtained with (F)-stereochemistry, indicative of CO insertion with the expected retention of alkene geometry. 

The insertion of carbon monoxide into o-alkylpalladium(II) complexes followed by attack by either alcohols or amines is a powerful acylation method. This carbonylation reaction has been applied in several different ways to the reactions and syntheses of indoles. Hegedus and coworkers converted o-allylanilines to indoline esters 315 in yields up to 75% [293], In most of the examples in this section, CO at atmospheric pressure was employed. 

Complex condensation products are obtained by reaction of the alkyne complex with excess of 3,3-dimethyl-l-butyne, which yields two isomeric products of formulas Ru3(CO)6[HC2C(Me)3-COCH2CMe3][HC2CMe3]2 (125). The X-ray structure of one of those adducts (Fig. 19) shows that both dimerization of two alkyne molecules and the insertion of carbon monoxide into the alkyne metal bonds have occurred. The Ru-Ru distances of 2.820,2.828, and 2.686 A in the ring are of interest. The value of 2.686 A is one of the shortest found in a... 

The carbonylation reaction (Eq. 1) involves formal insertion of carbon monoxide into the C - 0 bond of methanol ... 

The metal hydride bond is stronger than a metal carbon bond and the insertion of carbon monoxide into a metal hydride is thermodynamically most often uphill. Alkene insertion into a metal hydride is thermodynamically allowed and often reversible. 

While transition metals have been used extensive ) in C-gly coside construction, assigning a precise reactivity profile to C(l) can be difficult and this section will cover cases where nucleophilic character is apparent, albeit loosely defined. The use of palladium-mediated synthesis of C-glycosides has been reported and this topic, which involves an anomeric tin intermediate, has been covered in Sect. 2.2.2. The insertion of carbon monoxide into a carbon-metal (C(l)-metal) bond is, however, an important aspect of transition metal-mediated C-glycoside formation, and this process has been observed and exploited in a number of situations. 

Metal-Oxygen Compounds. A few examples of the insertion of carbon monoxide into metal-oxygen groups have been reported. The best known is the reaction of mecuric acetate in methanol solution with carbon monoxide, forming methoxycarbonylmercuric acetate (83) which probably involves the following steps (32) ... 

Figure C shows carbon monoxide insertion reactions. There are a number of reduction reactions of carbon monoxide catalyzed by transition metals, and these, I believe, all involve an insertion of carbon monoxide into a metal hydride as an initial step. Cobalt hydrocarbonyl reacts with carbon monoxide to give formate derivatives. This is probably an insertion reaction also.

The insertion of alkynes into arylpalladium complexes might also be accompanied by the insertion of carbon monoxide into the resulting vinylpalladium intermediate. The carbonylative annulation of TV-protected 2-iodoanilines and internal alkynes under an ambient pressure of carbon monoxide resulted in the formation of 2-quinolones (4.14.), The protection of the nitrogen atom in the aniline is crucial to the success of the reaction. 

The insertion of carbon monoxide into azolylpalladium complexes proceeds readily and in most cases leads to the formation of carboxylic acid derivatives or ketones. In a modified version of the carbonylation 3-bromothiophene was reacted with carbon monoxide in the presence of sodium formate. This reagents converts the intermediate acylpalladium formate complex, through the release of carbon dioxide into the acylpalladium hydride (c.f 7.47.), which in turn releases thiophene carboxaldehyde as the sole product (6.62.),92 If sodium formate was replaced... 

The ready insertion of carbon monoxide into furanylpalladium complexes is impressively demonstrated by the reaction depicted in 6.63. The iodofiirane derivative was reacted with carbon monoxide in the presence of tetrabutylammonium chloride. Following an aqueous workup the appropriate carboxylic acid was isolated in good yield (6.63.).94 It is worth pointing out, that due to the mildness of the reaction conditions the Heck coupling of the olefin moiety could be excluded. 

Although the insertion of carbon monoxide into arylpaladium complexes at ambient pressure is well documented the analogous reaction of azinylpalladium complexes usually requires elevated pressures due to the electron deficient nature of these heterocycles. The reaction is commonly used to convert the haloazine into the appropriate carboxylic acid or hetaryl-ketone derivative. 

The mechanism for the reaction is believed to be as shown in Eq. 15.170 (start with CH3OH, lower right, and end with CHjCOOH, lower left).180 The reaction can be initiated with any rhodium salt, e.g., RhCl3, and a source of iodine, the two combining with CO to produce the active catalyst, IRItfCO y. The methyl iodide arises from the reaction of methanol and hydrogen iodide. Note that the catalytic loop involves oxidative addition, insertion, and reductive elimination, with a net production of acetic acid from the insertion of carbon monoxide into methanol. The rhodium shuttles between the +1 and +3 oxidation states. The cataylst is so efficient that the reaction will proceed at atmospheric pressure, although in practice the system is... 

The addition of carbon monoxide (1 atm) to a solution of compound 170 results in the formation of the new cyclic system 201 as a result of insertion of carbon monoxide into the Pd-S bond (Equation 21) <20040M2370>. 

Samarium-mediated functionalization also occurs in the case of N=N bonds [287]. A high yield (80%) double insertion of carbon monoxide into the N=N... 

Although the competing /i-hydrogcn abstraction is suppressed by the relatively fast insertion of carbon monoxide into the Pd C bond, two different modes of cyclopentene enchainment, namely by 1,2- and 1,3-insertion, have been recognised in the copolymers formed [29] ... 

Intramolecular insertion of carbon monoxide into the metal-carbene bond of the (Ej-isomer of D leads to the t/4-vinyl ketene complex intermediate E. Experimental support for this type of intermediate has been provided by the isolation of Cr( CO) 3-coordinated dienyl ketenes related to 5 (Scheme 4) [15a], and by trapping the vinyl ketene intermediates as vinyl lactone derivatives in the course of the reaction of chromium carbene complexes with 1-alkynols [15b]. 

Thermodynamically the insertion of an alkene into a metal-hydride bond is much more favourable than the insertion of carbon monoxide into a metal-methyl bond. The latter reaction is more or less thermoneutral and the equilibrium constant is near unity under standard conditions. The metal-hydride bond is stronger than a metal-carbon bond and the insertion of carbon monoxide into a metal hydride is thermodynamically most often uphill. Insertion of alkenes is also a reversible process, but slightly more favourable than CO insertion. Formation of new CT bonds at the cost of the loss of the ji bond of the alkene during alkene hydrogenation etc., makes the overall processes of alkenes thermodynamically exothermic, especially for early transition metals. 

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