Preparations with Carbon Monoxide

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. 

The linear a olefins described m Section 14 15 are starting materials for the preparation of a variety of aldehydes by reaction with carbon monoxide The process is called hydroformylation... 

Although these humble origins make interesting historical notes m most cases the large scale preparation of carboxylic acids relies on chemical synthesis Virtually none of the 3 X 10 lb of acetic acid produced m the United States each year is obtained from vinegar Instead most industrial acetic acid comes from the reaction of methanol with carbon monoxide... 

Most chromium-based catalysts are activated in the beginning of a polymerization reaction through exposure to ethylene at high temperature. The activation step can be accelerated with carbon monoxide. Phillips catalysts operate at 85—110°C (38,40), and exhibit very high activity, from 3 to 10 kg HDPE per g of catalyst (300—1000 kg HDPE/g Cr). Molecular weights and MWDs of the resins are controlled primarily by two factors, the reaction temperature and the composition and preparation procedure of the catalyst (38,39). Phillips catalysts produce HDPE with a MJM ratio of about 6—12 and MFR values of 90—120. 

The oldest method of preparation of ben2enehexol involves the reaction of molten potassium with carbon monoxide to give the potassium salt of the hexol the free phenol is obtained by neutrali2ation of the salt with dilute acid (263). This reaction has been reinvestigated and improved (264). 

I eopentanoic (Pivalic) Acid. Neopentanoic acid [75-98-9] is prepared using the Koch technology in which isobutylene reacts with carbon monoxide in the presence of strong acids such as H2SO4, HF, and BF H20 (119—122). General reaction conditions are 2—10 MPa (about 20—100 atm) of CO and 40-150°C. 

In an integrated continuous process, cellulose reacts with acetic anhydride prepared from the carbonylation of methyl acetate with carbon monoxide. The acetic acid Hberated reacts further with methanol to give methyl acetate, which is then carbonylated to give additional acetic anhydride (100,101). 

Hydroformylation (Section 17.5) An industrial process for preparing aldehydes (RCH2CH2CH=0) by the reaction of terminal alkenes (RCH=CH2) with carbon monoxide. 

As mentioned in the preceding section, the presence of water during the reaction of trialkylboranes with carbon monoxide inhibits the migration of the third alkyl group and leads to production of dialkyl ketones (i). This fact can be employed to advantage for the preparation of dialkyl ketones as shown in the scheme. 

Approximately 2.5 million tons of acetic acid is produced each year in the United States for a variety of purposes, including preparation of the vinyl acetate polymer used in paints and adhesives. About 20% of the acetic acid synthesized industrially is obtained by oxidation of acetaldehyde. Much of the remaining 80% is prepared by the rhodium-catalyzed reaction of methanol with carbon monoxide. 

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... 

Carboxylic acids can be prepared in moderate-to-high yields by treatment of diazonium fluoroborates with carbon monoxide and palladium acetate or copper(II) chloride. The mixed anhydride ArCOOCOMe is an intermediate that can be isolated. Other mixed anhydrides can be prepared by the use of other salts instead of sodium acetate." An arylpalladium compound is probably an intermediate." ... 

The diarsine and arsine/phosphine analogues of dppm have been used to prepare bridged diplatinum(I) complexes, in both cases with terminal chloro ligands.116,117 Both complexes react with carbon monoxide to produce carbonyl-bridged species. The mixed thio/phosphine ligand Ph2PCH2SMe (PS) also forms a diplatinum(I) complex by conproportionation of its dichloroplat-inum(II) complex with [Pt(dba)2].118 This dimer reacts with carbon monoxide to produce an unsupported dimer [PtCl(PS)(CO)]2 with the thioether arm of the Ph2PCH2SMe unbound. 

The polymers prepared from thexylborane and diene monomers were reacted with carbon monoxide at 120°C, followed by treatment with NaOH and H202 to produce a polyalcohol (scheme 5).13 This conversion includes migration of the polymer chain and thexyl group from the boron atom to carbon, as shown in scheme 5. When this reaction was carried out under milder condition, poly(ketone) segments were included in the polymer backbone due to an incomplete migration of the thexyl group. 

The preparation of carbonylmetals by treating a transition metal halide either with carbon monoxide and zinc, or with iron pentacarbonyl is well-known and smooth. However, a violent eruptive reaction occurs if a methanolic solution of a cobalt halide, a rhodium halide or a ruthenium halide is treated with both zinc and iron pentacarbonyl. 

As we have described previously, Ni(CO)4 can be prepared directly by the reaction of nickel with carbon monoxide. However, most of the binary metal carbonyls listed in Table 21.1 cannot be obtained by this type of reaction. A number of preparative techniques have been used to prepare metal carbonyls, and a few general ones will be described here. 

Other tin reagents have found use in Pd-catalyzed cross-couplings with halopyridines as well. The Stille coupling of 3-iodopyridine with ethoxy(tributylstannyl)acetylene gave rise to 3-ethoxyethynylpyridine (100), which was then hydrolyzed to the corresponding ethyl 3-pyridylacetate (101) [88], Carbamoylstannane 102 was prepared by sequential treatment of lithiated piperidine with carbon monoxide and trimethyltin chloride. Stille coupling of carbamoylstannane 102 and 3-bromopyridine provided a unique entry to amide 103 [89],... 

Like most aryl halides, furyl halides and furyl triflates have been coupled with a variety of organostannanes including alkenyl, aryl, and heteroaryl stannanes in the presence of catalytic palladium. Carbamoylstannane 66 was prepared by treating lithiated piperidine with carbon monoxide and tributyltin chloride sequentially. The Stille reaction of 66 and 3-bromofuran then gave rise to amide 67 [61]. In another example, lithiation of 4,4-dimethyl-2-oxazoline followed by quenching with MesSnCl resulted in 2-(tributylstannyl)-4,4-dimethyl-2-oxazoline (68) in 70-80% yield [62], Subsequent Stille reaction of 68 with 3-bromofuran afforded 2-(3 -furyl)-4,4-dimethyl-2-oxazoline (69). 

For preparative purposes the method of obtaining aldehydes from the primary alcohols is preferable by far, at least in the aliphatic series. The simple aromatic aldehydes can be obtained by alkaline hydrolysis of the arylidene chlorides, R.CHC12, which are produced from the hydrocarbons by substitution with chlorine (technical method for the preparation of benzaldehyde). In addition to these methods the elegant synthesis of Gattermann and Koch should be mentioned here. This synthesis, which proceeds like that of Friedel-Crafts, consists in acting on the aromatic hydrocarbon with carbon monoxide and hydrogen chloride in the presence of aluminium chloride and cuprous chloride. 

---