Ruthenium catalysts amidation

Partial hydrolysis of nitrile gives amides. Conventionally, such reactions occur under strongly basic or acidic conditions.42 A broad range of amides are accessed in excellent yields by hydration of the corresponding nitriles in water and in the presence of the supported ruthenium catalyst Ru(0H)x/A1203 (Eq. 9.19).43 The conversion of acrylonitrile into acrylamide has been achieved in a quantitative yield with better than 99% selectivity. The catalyst was reused without loss of catalytic activity and selectivity. This conversion has important industrial applications. 

Hydrogenation of amides normally result in the formation of alcohols, whereas lactams give cyclic amines. The work presented in this paper is the first example that we are aware in which a lactam was hydrogenated by a ruthenium catalyst. To verify that acid promoted the lactam carbonyl hydrogenation, two... 

Asymmetric amidation of sp C—H bonds was reported in good yields and moderate enantioselectivities (Scheme 5.27)." ° When benzylic or allylic C—H bonds were used, similar results were also obtained." In these reactions the prepared nitrenes, PhI=NTs, and/or PhI(OAc)2+NH2Ts were used as nitrogen atom transfer sources. The studies showed that Ru=NTs was formed in situ and acted as a possible active intermediate when a ruthenium catalyst was used (Figure 5.12), whereas a radical intermediate might be involved when a manganese catalyst was used. 

The direct addition of secondary amides to terminal alkynes has been successfully carried out in the presence of a ruthenium catalyst generated in situ from Ru (methallyl)2(cod) (2 mol%) as metal source, P"Bu3 (6 mol%) and dimethylaminopyr-idine (4mol%), in toluene at 100 °C [54]. Under these conditions the ( )-enamides vere stereoselectively formed from a variety of cyclic amides and ureas (Scheme 10.16). 

In 1989, a method for the peroxysilylation of alkenes nsing triethylsUane and oxygen was reported by Isayama and Mnkaiyama (eqnation 25). The reaction was catalyzed by several cobalt(II)-diketonato complexes. With the best catalyst Co(modp)2 [bis(l-morpholinocarbamoyl-4,4-dunethyl-l,3-pentanedionato)cobalt(n)] prodnct yields ranged between 75 and 99%. DiaUcyl peroxides can also be obtained starting from tertiary amines 87, amides 89 or lactams via selective oxidation in the a-position of the Af-fnnctional group with tert-butyl hydroperoxide in the presence of a ruthenium catalyst as presented by Murahashi and coworkers in 1988 ° (Scheme 38). With tertiary amines 87 as substrates the yields of the dialkyl peroxide products 88 ranged between 65 and 96%, while the amides 89 depicted in Scheme 38 are converted to the corresponding peroxides 90 in yields of 87% (R = Me) and 77% (R = Ph). 

In addition, the bisallylation of the two secondary amides of compound 91, followed by treatment with an appropriate ruthenium catalyst, allowed a tandem ringopening metathesis/ring-closing metathesis to give, after alcohol deprotection, the quite complex structure 92 [82]. 

Formation of amide 163 from 158 and 3,4-dimethoxyphenylethylamine 133, followed by a Bischler-Napieralski reaction and transfer-hydrogenation of the formed imine 164 with the ruthenium catalyst (S,S)-122 (Scheme 5.32) gave the enantion-pure epi-emetine analogue 161 (> 98% ee) and the enantioenriched diastereomer 162 (80% ee). 

Other processes involving metal catalysts like nickel(II), zinc(II), palladium(ll) and ruthenium(I) have not found broad application, but a related amidation of nitriles uses Ae ruthenium catalyst [RuH2(PPh3>4]. ... 

Among other ruthenium catalysts, the cluster Ru3(CO),2 has been found to efficiently catalyze the N-alkylation of amides, imides, and lactams by alcohols. Acetamide can be converted into A-ethylacetamide with ethanol, according to... 

Ruthenium catalysts can also be used in nitrene transfer reactions. The intramolecular amidation reactions of saturated C—H bonds have been developed with mthenium catalysts (Equation 11.23) [54]. In addition, the Ru-catalyzed asymmetric animation of benzylic and allylic C—H bonds has also been reported [55],... 

In general, ruthenium catalysts 86 are less active than 85 with respect to the formation of tri- and tetra-substituted alkenes. Although molybdenum catalyst 85 is appreciably sensitive to air and moisture, ruthenium catalysts 86 are not significantly affected. Both catalysts are tolerant of functionality in the substrate for example, ketones, esters, amides, epoxides, acetals, silyl ethers, amines, sulfides, and alcohols. 

Amide formation plays a very important role in chemical synthesis [1, 46]. Preparation of amides under neutral conditions and without generation of waste is a challenging goal [46-48]. Applying our pyridine-based ruthenium pincer complexes as catalysts, amides were synthesized directly from amines and alcohols or esters polyamides were obtained from diols and diamines, as delineated in this section. 

In 1999, Che and co-workers reported the first asymmetric Mn- and Ru-catalyzed asymmetric amidation reactions of saturated C—H bonds. As shown in Scheme 1.46, the chiral porphyrin with metal complexes C9 and CIO were prepared according to the procedures reported previously. Subsequently, amidation reactions were employed to test the efficiency of these two catalysts. Pleasingly, the amidated products were obtained with moderate yields and enantioselectivity. Under the same conditions, the manganese catalyst CIO affords the product in a considerably higher yield than the ruthenium catalyst C9. Interestingly, the enantiocontrol has a similar trend, the manganese catalyst CIO being more effective. Efforts have also been made to... 

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