Reaction carbonylation

The use of sihca gel-supported IL-phase catalyst in fixed-bed reactor might solve the leaciing problem partially [86]. Here, the model catalyst system is Rh(acac)(CO)2-ligand 1 or 2/[BMIm][PF5]/silica gel (Rh-1 and Rh-2), Scieme 2.20, and the model reaction is hydroformylation of l-octene. With a Hquid hourly space velocity of 16h i, the TOF of aldehyde formation was maintained at about 40 mol Rh h and the ratio of hnear and branch aldehyde was 2. Noteworthy, inductively coupled plasma atomic emission spectrometry (ICP-AES) analysis of outlet samples taken at steady-state conversion demonstrated rhochum metal leaching to be neghgible ( 0.7%, detection limit). 

In contrast, for SX/Rh ratios greater than 10, the excess SX might form the less active HRh(SX)2. Therefore, the optimized catalyst system should be as follows the pretreatment temperature of silica gel 100 °C the ligand/Rh ratio 10, and an IL loading corresponding to an a value of 0.2 (total IL volume/total pore volume of support). 

The Rh/PPh3/SILPC system can also be used in the hydroformylation reaction of unsaturated esters [96]. The aldehyde yields were about 90%, and the ratio between linear and branched aldehydes was up to 99. Followed by the condensation of the aldehyde with phenyl hydrazine, pyrazohn-5-one, which possesses biological properties such as an analgesic, antipyretic, antiphlogistic, antirheumatic, antiarthritic, and uricostiric, can be synthesized. 

At beginning, sihca-supported IL-phase catalyst, which was prepared by treating the silica gel in the acetone solution of IL [BMIm](BF4], was used in the synthesis of cyclic carbonate under supercritical conditions [101]. Epoxides with different structures could be efHciently transferred into cycHc carbonates with up 100% yields. The catalyst could be easily separated by filtration and reused for several runs without obvious deactivation. In order to simplify the separation of catalyst from the reaction mixture, sihca gel-modified magnetite was used as the support for covalent immobilization of IL, and similar results were obtained [102]. 

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Similarly to alkenes. alkynes also insert. In the reaction of 775 carried out under a CO atmosphere in AcOH, sequential insertions of alkyne, CO. alkene. and CO take place in this order, yielding the keto ester 776[483]. However, the same reaction carried out in THF in the presence of LiCl affords the ketone 777, but not the keto ester[484]. The tricyclic terpenoid hirsutene (779) has been synthesized via the Pd-catalyzed metallo-ene carbonylation reaction of 778 with 85% diastereoselectivity as the key reaction[485], Kainic acid and allo-kainic acid (783) have been synthesized by the intramolecular insertion ol an alkene in 780, followed by carbonylation to give 781 and 782[486],... 

Moderate yields of acids and ketones can be obtained by paHadium-cataly2ed carbonylation of boronic acids and by carbonylation cross-coupling reactions (272,320,321). In an alternative procedure for the carbonylation reaction, potassium trialkylborohydride ia the presence of a catalytic amount of the free borane is utilized (322). FiaaHy, various tertiary alcohols including hindered and polycycHc stmctures become readily available by oxidation of the organoborane iatermediate produced after migration of three alkyl groups (312,313,323). 

Acetates. Anhydrous iron(II) acetate [3094-87-9J, Ee(C2H202)2, can be prepared by dissolving iron scraps or turnings in anhydrous acetic acid ( 2% acetic anhydride) under an inert atmosphere. It is a colorless compound that can be recrystaUized from water to afford hydrated species. Iron(II) acetate is used in the preparation of dark shades of inks (qv) and dyes and is used as a mordant in dyeing (see Dyes and dye intermediates). An iron acetate salt [2140-52-5] that is a mixture of indefinite proportions of iron(II) and iron(III) can be obtained by concentration of the black Hquors obtained by dissolution of scrap iron in acetic acid. It is used as a catalyst of acetylation and carbonylation reactions. 

Aldehydes and Ketones. Pyrrole aldehydes and ketones are somewhat less reactive than the corresponding benzenoid derivatives. The aldehydes do not undergo Cannizzaro or Perkin reactions but condense with a variety of compounds that contain active methylene groups. They also react with pyrroles under acidic conditions to form dipyrryhnethenes (26). The aldehydes can be reduced to the methyl or carbinol stmctures. The ketones undergo normal carbonyl reactions. 

Unlike simple, unhindered carbonyl compounds, the quinones do not yield bisulfite addition products, but undergo ring addition. Another significant carbonyl reaction is the addition of tertiary phosphites under anhydrous conditions (98). The ester product (99) is easily hydroly2ed, and the overall sequence produces excellent yields of hydroquinone monoethers. 

Hydroformylation. Probably the best known catalytic carbonylation reaction is the hydroformylation, or 0x0 reaction, for producing aldehydes and alcohols from carbon monoxide, hydrogen, and olefins (eq. 9) (36). 

Other standard carbonyl reactions also occur readily. Thus 5-acetyl-3-methoxyisoxazole... 

In some cases, a simple carbonyl reaction with the CH-acidic cyclopenta-dienes in the presence of a base gave a convenient entry to special types of azafulvalenes. Starting from the appropriate cyclic carbonylic and thiocar-bonylic systems respectively, or their acetals, the following azafulvalenes... 

The term Knoevenagel reaction however is used also for analogous reactions of aldehydes and ketones with various types of CH-acidic methylene compounds. The reaction belongs to a class of carbonyl reactions, that are related to the aldol reaction. The mechanism is formulated by analogy to the latter. The initial step is the deprotonation of the CH-acidic methylene compound 2. Organic bases like amines can be used for this purpose a catalytic amount of amine usually suffices. A common procedure, that uses pyridine as base as well as solvent, together with a catalytic amount of piperidine, is called the Doebner modification of the Knoevenagel reaction. 

H)-Naphthalenone, 4,4a,5,6 7,8-hexahydro, 46, 80 4-( -Naphthyl) 2 butanone, 47, 89 Nickel carbonyl, reaction with 3,4-dichloro-l,2,3,4-tetramethylcy-clobutene 46, 36... 

Besides acylation and alkylation reactions, typical carbonyl reactions, such as reduction and substitution, are known. Thus, the oxo group in position 3 of 8 is attacked by sodium cyanide, resulting in the cyanohydrin in 55% yield. Subsequent dehydration with p-toluene-sulfonic acid and acetylation in position 5 gives 1-benzothiepin 12.90... 

Molybdenum, tris(phenylenedithio)-structure, 1,63 Molybdenum alkoxides physical properties, 2,346 synthesis, 2,339 Molybdenum blue liquid-liquid extraction, 1,548 Molybdenum cofactor, 6,657 Molybdenum complexes acrylonitrile, 2,263 alkoxides, 3,1307 alkoxy carbonyl reactions, 2,355 alkyl, 3,1307 alkyl alkoxy reactions, 2,358 alkyl peroxides oxidation catalyses, 6,342 allyl, 3,1306... 

Tungsten complexes, 3, 973-1015 alkoxy carbonyl reactions, 2, 355 alkyl alkoxy reactions, 2, 358 amides... 

According to the above reaction scheme the carbonylation reaction has to be carried out in two steps In the absence of water the olefin is first converted at 20-80°C and 20-100 bar by the aid of mineralic acid and carbon monoxide into an acyliumion. In a second step the acyliumion reacts with water to the carboxylic acid. The mineral acid catalyst is recovered and can be recycled. The formation of tertiary carboxylic acids (carboxylic acids of the pivalic acid type) is enhanced by rising temperature and decreasing CO pressure in the first step of the reaction. Only tertiary carboxylic acids are formed from olefins that have at the same C atom a branching and a double bond (isobutylene-type olefins). 

The equilibrium constant K is the same for R =t-C4HJ and t-CsHi. As also the rate constants of carbonylation and decarbonylation are about equal for these two ions, it is concluded that both the thermodynamics and the kinetics of the carbonylation reaction are independent of the structure of R+, if R+ is an acyclic tertiary alkyl cation. This agrees with former findings (Brouwer, 1968) on the relative stabilities of such ions. 

Yoneda, N. Takahashi, Y Fukuhara, T. Suzuki, A. Bull. Chem. Soc. Jpn., 1986,59,2819. For reviews of other carbonylation reactions of alcohols and other saturated oxygenated compounds, see Bahrmann, H. Comils, B. in Falbe New Syntheses with Carbon Monoxide, Springer NY, 1980, p. 226 Piacenti, F. Bianchi, M. in Wender Pino Organic Syntheses via Metal Carbonyls, vol. 2 Wiley NY, 1977, p. 1. 

For the nickel carbonyl reaction, the addition is syn for both alkenes and alkynes. The following is the accepted mechanism ... 

The importance of these and related processes in hydroformylation and other carbonylation reactions has been underscored by several reviewers 62,115,118) and will not be reiterated here. 

Carbon monoxide insertion into Ni—C bonds has been postulated in carbonylation reactions involving (7r-C3H5NiX)2 (X = C1, Br, or I) (112, 123a). 

Palladium(O)- and Pd(II)-catalyzed carbonylation reactions have been the subject of several recent articles 32, 116, 119, 124, 173, 228, 232). In one case, the attending CO insertion into a Pd—C bond was shown to proceed with retention of configuration at carbon 131a, 218). 

An iron-catalyzed carbonylation reaction of alkynes 120 forming succinimides 121 by the aid of Fe(CO)5 78 or [Fe3(CO)i2] 119 has been reported by Beller et al. (Scheme 31) [94]. This reaction seems interesting as iron-carbonyl complexes are kinetically relatively inert. As a model system 3-hexyne was reacted with excess ammonia under 20 bar CO pressure. Employing a higher pressure leads to... 

Carbonylation reactions encompass a diverse set of transformations used to synthesise many important high-value fine chemicals, synthetic intermediates and materials such as polycarbonates [36]. Palladium catalysts modified with PRj ligands facilitate these reactions. However, carbonylation often requires harsh conditions, especially for less reactive C-X bonds, thereby promoting catalyst degradation via P-C bond cleavage. The strength of the NHC bond may demonstrate the utility of... 

Carbonyl reactions are extremely important in chemistry and biochemistry, yet they are often given short shrift in textbooks on physical organic chemistry, partly because the subject was historically developed by the study of nucleophilic substitution at saturated carbon, and partly because carbonyl reactions are often more difhcult to study. They are generally reversible under usual conditions and involve complicated multistep mechanisms and general acid/base catalysis. In thinking about carbonyl reactions, 1 find it helpful to consider the carbonyl group as a (very) stabilized carbenium ion, with an O substituent. Then one can immediately draw on everything one has learned about carbenium ion reactivity and see that the reactivity order for carbonyl compounds ... 

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