Carbon monoxide formylation with

Formamides are usually not deprotonated a to nitrogen but at the formyl group [227-231], The resulting carbamoyl lithium derivatives (R2NCOLi), which can also be generated from deprotonated amines [351] or amides [352] and carbon monoxide, react with electrophiles E+ to yield the expected products (R2NCOE), despite the carbene character and consequent low stability of these intermediates [179, 351] (Scheme 5.39, see Section 5.4.7). Palladium-catalyzed versions of the reaction have been reported [353, 354],... 

The reaction of trivalent carbocations with carbon monoxide giving acyl cations is the key step in the well-known and industrially used Koch-Haaf reaction of preparing branched carboxylic acids from al-kenes or alcohols. For example, in this way, isobutylene or tert-hutyi alcohol is converted into pivalic acid. In contrast, based on the superacidic activation of electrophiles leading the superelectrophiles (see Chapter 12), we found it possible to formylate isoalkanes to aldehydes, which subsequently rearrange to their corresponding branched ketones. 

Protonation of formic acid similarly leads, after the formation at low temperature of the parent carboxonium ion, to the formyl cation. The persistent formyl cation was observed by high-pressure NMR only recently (Horvath and Gladysz). An equilibrium with diprotonated carbon monoxide causing rapid exchange can be involved, which also explains the observed high reactivity of carbon monoxide in supera-cidic media. Not only aromatic but also saturated hydrocarbons (such as isoalkanes and adamantanes) can be readily formylated. 

Intermediate formation of formyl chloride is not necessary since the actual alkylating agent, HCO", can be produced by protonation of carbon monoxide or its complexes. However, it is difficult to obtain an equimolar mixture of anhydrous hydrogen chloride and carbon monoxide. Suitable laboratory preparations involve the reaction of chlorosulfonic acid with formic acid or the reaction of ben2oyl chloride with formic acid ... 

Hydroformylation. Esters of maleate and fumarate are treated with carbon monoxide and hydrogen in the presence of appropriate catalysts to give formyl derivatives. Dimethyl fumarate [624-49-7] is hydroformylated in 1 1 CO/H2 at 100°C and 11.6 MPa pressure with a cobalt [7440-48-4] catalyst to give an 83% yield of dimethyl formylsuccinate [58026-12-3] product (72). 

Quaternary Salts. Herbicides paraquat (20) and diquat (59) are the quaternary salts of 4,4 -bipyridine (19) and 2,2 -bipyridine with methyl chloride and 1,2-dibromoethane, respectively. Higher alkylpyridinium salts are used in the textile industry as dye ancillaries and spin bath additives. The higher alkylpyridinium salt, hexadecylpytidinium chloride [123-03-5] (67) (cetylpyridinium chloride) is a topical antiseptic. Amprolium (62), a quaternary salt of a-picohne (2), is a coccidiostat. Bisaryl salts of butylpyridinium bromide (or its lower 1-alkyl homologues) with aluminum chloride have been used as battery electrolytes (84), in aluminum electroplating baths (85), as Friedel-Crafts catalysts (86), and for the formylation of toluene by carbon monoxide (87) (see QuaternaryAA ONiUM compounds). 

The idea that dichlorocarbene is an intermediate in the basic hydrolysis of chloroform is now one hundred years old. It was first suggested by Geuther in 1862 to explain the formation of carbon monoxide, in addition to formate ions, in the reaction of chloroform (and similarly, bromoform) with alkali. At the end of the last century Nef interpreted several well-known reactions involving chloroform and a base in terms of the intermediate formation of dichlorocarbene. These reactions included the ring expansion of pyrroles to pyridines and of indoles to quinolines, as well as the Hofmann carbylamine test for primary amines and the Reimer-Tiemann formylation of phenols. 

Another formylation reaction, which is named after Gattermann, is the Gatter-mann-Koch reaction. This is the reaction of an aromatic substrate with carbon monoxide and hydrogen chloride (gas) in the presence of a Lewis acid catalyst. Similar to the Gattermann reaction, the electrophilic agent 9 is generated, which then reacts with the aromatic substrate in an electrophilic aromatic substitution reaction to yield the formylated aromatic compound 10 ... 

Mesitaldehyde may be prepared from mesitylmagnesium bromide by the reaction with orthoformate esters3 or ethoxy-methyleneaniline 3 from acetylmesitylene by oxidation with potassium permanganate,4 from mesitoyl chloride by reduction,5 from mesityllithium by the reaction with iron pentacarbonyl and from mesitylene by treatment with formyl fluoride and boron trifluoride,7 by treatment with carbon monoxide, hydrogen chloride, and aluminum chloride,8 or by various applications of the Gatterman synthesis.9-11... 

Abstract This chapter focuses on carbon monoxide as a reagent in M-NHC catalysed reactions. The most important and popular of these reactions is hydro-formylation. Unfortunately, uncertainty exists as to the identity of the active catalyst and whether the NHC is bound to the catalyst in a number of the reported reactions. Mixed bidentate NHC complexes and cobalt-based complexes provide for better stability of the catalyst. Catalysts used for hydroaminomethylation and carbonyla-tion reactions show promise to rival traditional phosphine-based catalysts. Reports of decarbonylation are scarce, but the potential strength of the M-NHC bond is conducive to the harsh conditions required. This report will highlight, where appropriate, the potential benefits of exchanging traditional phosphorous ligands with iV-heterocyclic carbenes as well as cases where the role of the NHC might need re-evaluation. A review by the author on this topic has recently appeared [1]. 

Carbon monoxide, hydrogen cyanide, and nitriles also react with aromatic compounds in the presence of strong acids or Friedel-Crafts catalysts to introduce formyl or acyl substituents. The active electrophiles are believed to be dications resulting from diprotonation of CO, HCN, or the nitrile.64 The general outlines of the mechanisms of these reactions are given below. 

A cracker converts isobutyraldehyde at a pass yield of 80 per cent back to propylene, carbon monoxide and hydrogen by passage over a catalyst with steam. After separation of the water and unreacted isobutyraldehyde the cracked gas is recycled to the hydro-formylation reactor. The isobutyraldehyde is recycled to the cracker inlet. The operating conditions of the cracker are 275°C and 1 bar. 

An attempt to formylate phenol by heating a mixture with nitromethane and aluminium chloride in an autoclave under carbon monoxide at 100 bar pressure at 110°C led to a high-energy explosion after 30 min. 

Under a pressure (20 bar) of carbon monoxide, carbonylative silylcarbocyclization of enyne 92 was examined in the presence of a cationic rhodium-BINAP catalyst (Scheme 31).86 Although the enantioselectivity is low, the five-membered carbocycle functionalized with an alkenylsilane moiety and a formyl group was obtained with high selectivity. 

The range of the reaction was extended by the elegant aldehyde synthesis of Gattermann and Koch. If a mixture of carbon monoxide and hydrogen chloride is allowed to act in the presence of aluminium chloride (and cuprous chloride) on toluene (benzene is less suitable), the reaction occurs which might he expected with formyl chloride if this substance were capable of existence. 

In contrast, spectroscopic and crystal structure analysis indicates that nucleophilic attack of hydride on 72 occurs on the face of the ligand which is coordinated to the metal (Scheme 17). No intermediate species could be detected for this latter reaction. Monitoring of the reduction of the rhenium analog 74 with sodium borohydride indicated the intermediacy of a rhenium formyl complex 75, presumably formed by attack on a coordinated carbon monoxide. Signals for 75 eventually disappear and are replaced by those of the (diene)rhenium product 76 (Scheme 18)95. 

Zerovalent transition metal carbonyl moieties may act as electron acceptors, and thus activate coordinated polyene ligands toward nucleophilic attack. Reaction of (C.411<5 )-Fe(CO)3 with KBHEt3 (—80 °C) proceeds via attack at a coordinated carbon monoxide to generate the anionic iron-formyl species 185 (Scheme 47)184. Upon warming to... 

Photolytic. Irradiation of vinyl chloride in the presence of nitrogen dioxide for 160 min produced formic acid, HCl, carbon monoxide, formaldehyde, ozone, and trace amounts of formyl chloride and nitric acid. In the presence of ozone, however, vinyl chloride photooxidized to carbon monoxide, formaldehyde, formic acid, and small amounts of HCl (Gay et al, 1976). Reported photooxidation products in the troposphere include hydrogen chloride and/or formyl chloride (U.S. EPA, 1985). In the presence of moisture, formyl chloride will decompose to carbon monoxide and HCl (Morrison and Boyd, 1971). Vinyl chloride reacts rapidly with OH radicals in the atmosphere. Based on a reaction rate of 6.6 x lO" cmVmolecule-sec, the estimated half-life for this reaction at 299 K is 1.5 d (Perry et al., 1977). Vinyl chloride reacts also with ozone and NO3 in the gas-phase. Sanhueza et al. (1976) reported a rate constant of 6.5 x 10 cmVmolecule-sec for the reaction with OH radicals in air at 295 K. Atkinson et al. (1988) reported a rate constant of 4.45 X 10cmVmolecule-sec for the reaction with NO3 radicals in air at 298 K. 

In sharp contrast to the unique pattern for the incorporation of carbon monoxide into the 1,6-diyne 63, aldehyde 77 was obtained as the sole product in the rhodium-catalyzed reaction of 1,6-enyne 76 with a molar equivalent of Me2PhSiH under CO (Scheme 6.15, mode 1) [22]. This result can be explained by the stepwise insertion of the acetylenic and vinylic moieties into the Rh-Si bond, the formyl group being generated by the reductive elimination to afford 77. The fact that a formyl group can be introduced to the ole-finic moiety of 76 under mild conditions should be stressed, since enoxysilanes are isolated in the rhodium-catalyzed silylformylation of simple alkenes under forcing conditions. The 1,6-enyne 76 is used as a typical model for Pauson-Khand reactions (Scheme 6.15, mode 2) [23], whereas formation of the corresponding product was completely suppressed in the presence of a hydrosilane. The selective formation of 79 in the absence of CO (Scheme 6.15, mode 3) supports the stepwise insertion of the acetylenic and olefmic moieties in the same molecules into the Rh-Si bond. 

A ketone can also be formed with a Friedel-Crafts acylation. The process requires an acid chloride and an aromatic compound. An aldehyde can t be formed by this procedure because the appropriate acid chloride, formyl chloride (HCOCl), is unstable and decomposes to carbon monoxide and hydrogen chloride. Figure 10-12 illustrates the preparation of acetophenone from benzene and acetyl chloride. 

The last explanation for methanol formation, which was proposed by Ponec et al., 26), seems to be well supported by experimental and theoretical results. They established a correlation between the gfiethanol activity and the concentration of Pd , most probably Pd. Furthermore, Anikin et al. (27) performed ab initio calculations and found that a positive charge on the palladium effectively stabilizes formyl species. Metals in a non-zero valent state were also proposed by Klier et al. (28) on Cu/ZnO/Al O, by Apai (29) on Cu/Cr O and by Somorjai for rhodium catalyts (30). Recently results were obtained with different rhodium based catalysts which showed the metal was oxidized by an interaction with the support (Rh-0) (on Rh/Al 0 ) by EXAFS ( -32) and by FT-IR ( ) and on Rh/MgO by EXAFS ( ). The oxidation of the rhodium was promoted by the chemisorption of carbon monoxide (, ). ... 

The HCo(CO)4 complex is therefore inferred to be involved in initial hydrogen transfer to carbon monoxide. This step was initially proposed to comprise rate-determining hydrogen atom transfer from HCo(CO)4 to free CO, affording a formyl radical, HtO subsequent reaction with further HCo(CO)4 would lead to the observed products (35). However, kinetic observations (the zero-order dependence on CO partial pressure) were later made which are inconsistent with such a process (36). 

A detailed description of the prepn of 4 amino-y-sym-triazole by heating formylhydra-zine at 150—200° is given in Ref 3 Formyl-hydrazine was obtained by heating a mixt of ethylformate and hydrazine hydrate in ale fat 18 hours. In Refs 4 5 is described a method of prepn of this a min otri azole starting with the treatment of hydrazine hydrate and carbon monoxide at high pressure and elevated temps... 

Zirconium hydride reactivity with carbon monoxide demonstrates the strong driving force toward products with a Zr-O bond. Indeed, the facility of the CO migratory insertion into Zr-C and especially Zr-H bonds may be from a carbonyl oxygen-zirconium interaction that stabilizes the transition state to the acyl and formyl complexes. 

Formylation of isobutane with carbon monoxide in the presence of an excess of A1C13 was first reported by Nenitzescu to yield, among others, methyl isopropyl ketone (31%).168 A new highly efficient superelectrophilic formylation-rearrange-ment of isoalkanes by Olah and coworkers has been described.282 Selective formation of branched ketone in high yield with no detectable branched acids, that is, the Koch products, was achieved. A particularly suitable acid is HF—BF3, which transforms, for example, isobutane to methyl isopropyl ketone in 91% yield. The... 

Organometallic complexes frequently are susceptible to nucleophilic attack by an external reagent. In some instances the attack takes place on the metal center (see substitution reactions, page 686). while in others it occurs on a bound ligand. Already in this chapter we have seen many instances in which coordinated carbon monoxide undergoes nucleophilic attack. Examples include reactions with H to produce a formyl complex (Eq. 15.19). with R to form an acyl complex (Eq. 15.49). and with OH to give a hydroxycarbonyl complex (Eq. 15.21). 

As with the simple alkylcoumarins, phenylcoumarins readily eliminate carbon monoxide from the molecular ion. Mass spectral fragmentation of 4-phenylcoumarin follows the route given in Scheme 10. The molecular ion (122a) appears as the base peak. Formyl radical elimination from (122b) produces the fluorenyl cation (122c), m/e 165 (63TL891). 

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