Ketones catalyst effect

In the early 1920s Badische Arulin- und Soda-Fabrik aimounced the specific catalytic conversion of carbon monoxide and hydrogen at 20—30 MPa (200—300 atm) and 300—400°C to methanol (12,13), a process subsequendy widely industrialized. At the same time Fischer and Tropsch aimounced the Synth in e process (14,15), in which an iron catalyst effects the reaction of carbon monoxide and hydrogen to produce a mixture of alcohols, aldehydes (qv), ketones (qv), and fatty acids at atmospheric pressure. 

The most selective 4-substitution is obtained in the Friedel-Crafts isopropylation of 2-acetylthiophene, which under certain conditions gives as much as 99% of this isomer and 1% of the 5-isomer. An--other case of selective 4-substitution is the bromination of 2-thienyl alkyl ketones using the swamping catalyst effect (i.e., brominating in the presence of excess AlCb without solvent), which yields 43-63% of apparently isomer-free 4-bromo-2-thienyl alkyl ketones. Gold-farb et al. also have applied this method to the chloromethylation of... 

Wacker oxidation of l-alkenes. The Wacker oxygenation of 1-alkenes to methyl ketones involves air oxidation catalyzed by PdCl2 and CuCU, which is necessary for reoxidation of Pd(0) to Pd(II).1 This oxygenation is fairly sluggish and can result in chlorinated by-products. A new system is comprised of catalytic amounts of Pd(OAc)2, hydroquinone, and 1, used as the oxygen activator.2 The solvent is aqueous DMF, and a trace of HClOj is added to prevent precipitation of Pd(0). Oxygenation using this system of three catalysts effects Wacker oxidation of 1-alkenes in 2-8 hours and in 67-85% yield. 

Synthesis of Methyl Isobutyl Ketone over a Multifunctional Heterogeneous Catalyst Effect of Metal and Base Components on... 

The catalytic hydrosilylation of ketones is a useful substitute for hydrogenation. As shown in Scheme 7, the strong affinity of silicon for oxygen facilities the reaction of ketones 11a, 18). The DIOP-based Rh catalysts effect enantioselective hydrosilylation of a- and 7-keto esters... 

Oxidation of allylic andhomallylic acetates (cf. 10,175-176).1 This system is an efficient catalyst for oxygenation of terminal alkenes to methyl ketones (Wacker process). Similar oxidation of internal olefins is not useful because it is not regioselective. However, this catalyst effects oxygenation of allylic ethers and acetates regioselectively to give the corresponding /i-alkoxy ketones in 40-75% yield. Under the same conditions, homoallylic acetates are oxidized to y-acetoxy ketones as the major products. 

Michael additions of C-nudeophiles such as the indanone 1 have been the subject of numerous further studies For example, the reaction between the indanone 1 and methyl vinyl ketone was effected by a solid-phase-bound quinine derivative in 85% yield and with remarkable 87% ee by d Angelo, Cave et al. [5], Co-polymers of cinchona alkaloids with acrylonitrile effected the same transformation Kobaya-shi and Iwai [6a] achieved 92% yield and 42% ee and Oda et al. [6b] achieved almost quantitative yield and up to 65% ee. Similarly, partially resolved 2-(hydroxy-methyl)quinudidine was found to catalyze the reaction between 1 and acrolein and a-isopropyl acrolein with induction of asymmetry, but no enantiomeric excesses were determined [7]. As shown in Scheme 4.4, the indanone 7 could be added to MVK with up to 80% ee under phase-transfer conditions, by use of the Cinchona-derived PT-catalysts 9a and 9b, affording the Michael-product 8 or enf-8, respectively [8]. The adducts 8 or ent-8 were intermediates in the stereoselective Robinson anellation of a cydohexenone ring to the indanone 7 [8],... 

During our further studies of ketone catalysts, ketone 16 was found to be highly enantioselective for a number of acyclic and cyclic d.s-olefins (Table 10.6).73-74 It is important to note that the epoxidation is stereospecific with no isomerization observed in the epoxidation of acyclic systems. Ketone 16 also provides encouragingly high ee s for certain terminal olefins, particularly styrenes.74-75 In general, ketones 1 and 16 have complementary substrate scopes. In our subsequent study of the conformational and electronic effects of ketone catalysts on epoxidation, ketone 17, a carbocyclic analog of 16, was found to be highly enantioselective for various styrenes (Table 10.7).76... 

TABLE 5.3 Time (min) for the Hydrogenation of Ketones over Raney Nickel Catalyst Effects of Promoters 1 ... 

A number of ketone catalysts have been developed. Crucial considerations are solubility and stability. As an example, catalytic amounts of ammonium salts such as Thexyl-l-methyl-4-oxopiperidinium triflate with Oxone in a buffered water-dichloromethane mixture are effective oxidation agents (Equation 69) <1995JOC1391>. Other... 

A further series of ketone catalysts containing spiro ethers and lactones have been examined in the asymmetric epoxidation of phenylcyclohexene (cf Table 5, entry 2 94% yield, 98% ee) (Figure 11). The substituents on the spiro ring appeared to effect enantioselectivity both sterically and electronically <2005T6409>. 

BINAP-Ru complexes show an excellent enantioselectivity in the hydrogenation of a-, /3-, or y-amino, -hydroxy, and -alkoxy ketones. Thus, a-dialkylamino ketones are effectively converted by (S)-BINAP-RuCl2 complexes to the chiral /3-amino alcohols with up to 99% e.e. (Eq. 2.25) [119, 120]. A normally unreactive Ru diacetate complex may be used for the hydrogenation of a-dimethylaminoacetone [119]. With a trans-RuCl2 (R)-xylbinap (R)-daipen ((R,R)-20)/KOC(CH3)3 catalyst system, a variety of a- and /3-amino ketones are hydrogenated in high optical yields [114]. Thus, a-(dimethylamino)acetone is converted to the S amino alcohol in 92% e.e. with an S/C of 2000 under 8 atm H2, whereas a-(dimethylamino)acetophenone is converted to the R alcohol in 93% e.e. with the same catalyst. The reversed sense of... 

A BINAP-Ru catalyst effectively discriminates between a hydroxy group and an alkoxy or aryloxy group, and even between u-octadecyl and triphenylmethoxy groups [174]. The S enantiomer of racemic l-hydroxy-l-phenyl-2-propanone is selected by (R)-BINAP-Ru complex to be hydrogenated to the corresponding 1S,2R diol in 92% e.e. (50.5%, syn-.anti = 98 2) [5c]. The rmreacted R hydroxy ketone in 92% e.e. (49.5%) is recovered, and the relative hydrogenation rate of the enantiomers, ks/kn, is calculated to be 64 1. 

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