Amides aerobic oxidation

Chiral A-salicylidene vanadyl carboxylates are efficient catalysts for asymmetric aerobic oxidation of a-hydoxy esters and amides with divergent substituents. These catalysts have been explored for the kinetic resolution of secondary alcohols also. The stereochemical origin of the almost total asymmetric control has been probed.262... 

J.K. Cha et al. developed a stereocontrolled synthesis of bicyclo[5.3.0]decan-3-ones from readily available acyclic substrates. Acyclic olefin-tethered amides were first subjected to the intramolecular Kulinkovich reaction to prepare bicyclic aminocyclopropanes. This was followed by a tandem ring-expansion-cyclization sequence triggered by aerobic oxidation. The reactive intermediates in this tandem process were aminium radicals (radical cations). The p-anisidine group was chosen to lower the amine oxidation potential. This substituent was crucial for the generation of the aminium radical (if Ar = phenyl, the ring aerobic oxidation is not feasible). 

Arylacetamides undergo aerial oxidation to yield the corresponding a-keto amides without the need of a transition metal salt. The transformation is carried out in the presence of a base (CS2CO3) and Bu4NBr. Primary amines are converted into oximes in an aerobic oxidation employing l,l-diphenyl-2-picrylhydrazyl (1) and WO3/AI2O3 as catalyst. ... 

Hexahydrohomofolic acid (V.36) was synthesized by Nair et al. [221] by condensation of 2,4-diamino-6-chloro-5-nitropyrimidine with the amino ketal (V.37), followed by ketal acidolysis, reductive cyclization to a 7,8-dihydropteridine, aerobic oxidation, ester hydrolysis, A, A -bis(tri-fluoroacetylation), mixed anhydride condensation with diethyl L-glutamate, and cleavage of the ester and amide groups with base. Ketal (V.37) was... 

Leow reported the use of a phenazinium salt, either phenazine ethosulfate or saffanin O, as a photocatalyst for the aerobic oxidative amidation of aromatic aldehydes with secondary amines to prepare the corresponding amides in good to high yields (Scheme 62) (140L5812).This method provides access to a more ecologically safe, mild, and inexpensive generation of benzamides. 

For the synthesis of quinazoHnones 147, a domino UUmann-type cou-pling/aerobic oxidative C-H amidation/oxidation process was successfully utilized by Fu et ol. [79]. 

In this domino process, benzylamine was reacted with 2-halobenzamides through UUman-type coupling to yield the N-arylated intermediate 144 (Scheme 9.26). Then, a copper-catalyzed aerobic oxidation of 144 afforded the intermediate 145, which underwent an intramolecular nucleophilic addition of the amide to provide 146. Under the used reaction conditions, the intermediate 146 was oxidized to provide the desired products 147 in excellent yield. This protocol was also utilized by Fu et al. [80] by employing easily available a-amino adds instead of benzylamines to synthesize similar analogs. Very recently, the same method was applied for the synthesis of pyrimido[4,5-b]carbazoles by Nagarajan et al. [81]. 

The CDC between A-f-butyl nitrones and terminal alkynes to form alkynylated nitrones in good to excellent yields, catalysed by zinc trifiate, was achieved using 3,3, 5,5 -tetra-tertbutyldipheno-quinone and O2 as oxidants. The alkynylated nitrones were transformed to regioisomerically pure 3,5-disubstituted isoxazoles. Experimental and DFT computational studies of Pd(OAc)2/pyridine-catalysed intramolecular aerobic oxidative amination of alkenes supported a stepwise mechanism that involved (i) the formation of a Pd(ll)-amidate-alkene chelate with release of 1 equiv. of pyridine and AcOH from the catalyst centre, (ii) insertion of alkene into a Pd—N bond. 

So, M., Liu, Y, Ho, C., et al. (2009). Graphite-Supported Gold Nanoparticles as Efficient Catalyst for Aerobic Oxidation of Benzyhc Amines to Imines and N-Substituted 1,2,3,4-Tetrahydroisoquinolines to Amides Synthetic Apphcations and Mechanistic Study, Chemistry —An Asian Journal, 4, pp. 1551-1561. 

In 2008, the Stahl group published the first copper-catalyzed aerobic oxidative amidation of terminal alkynes [200]. An extensive screening of various copper sources, Br0nsted bases, and solvents led to the optimal conditions shown in Scheme 4.51. 

The effect of amine ligands in copper(I)-catalyzed chemose-lective amide carbamoylation has been studied. Catalytic asymmetric synthesis of binaphthol derivatives is also reported by aerobic oxidative coupling of 3-hydroxy-2-naphthoates with chiral diamine-copper complexes (eq 15). ... 

A plausible mechanism of this amides synthesis via C-C bond cleavage of aryl alkyl was shown in Scheme 3.13. The carbonyl group is initially attacked by the azide to form the unstable intermediate 26 which is a potentially reversible process. Subsequently, intermediate 27 is formed via aerobic oxidation process under C11/O2 oxidative system. Then an imidic acid intermediate 29 is generated through... 

Kegnaes S, Mielby J, Mentzel UV, Jensen T, Fristrup P, Riisager A (2012) One-pot synthesis of amides by aerobic oxidative coupling of alcohols or aldehydes with amines using supported gold and base as catalysts. Chem Commun 48(18) 2427-2429... 

Molla RA, Ghosh K, Tuhina K, Manirul Islam S (2015) An aerobic oxidative synthesis of aryl nitriles and primary aryl amides from benzylie alcohols catalyzed by a polymer supported Cu(II) complex. New J Chem 39(2) 921-930... 

Notably, in the cobalt catalyzed aerobic oxidative amidation of toluene, Mizuno and co-workers discovered that benzonitrile was formed as the major product by using urea as nitrogen source [117]. When amorphous Mn02 was employed, the formation of benzamide turned to be the dominant process (Scheme 4.20). 

A-Alkylation of amides and amines and dehydrative -alkylation of secondary alcohols and a-alkylation of methyl ketones " have been carried out by an activation of alcohols by aerobic oxidation to aldehydes, with copper(II) acetate as the only catalyst. A relay race process rather than the conventional borrowing hydrogen-type mechanisms has been proposed for the aerobic C-alkylation reactions, based on results of mechanistic studies. A Winterfeldt oxidation of substituted 1,2,3,4-tetrahydro-y-carboline derivatives provides a convenient and efiflcient method for the synthesis of the corresponding dihydropyrrolo[3,2-fc]quinolone derivatives in moderate to excellent yields. The generality and substrate scope of this aerobic oxidation have been explored and a possible reaction mechanism has been proposed. Direct oxidative synthesis of amides from acetylenes and secondary amines by using oxygen as an oxidant has been developed in which l,8-diazabicyclo[5.4.0]undec-7-ene was used as the key additive and copper(I) bromide as the catalyst. It has been postulated that initially formed copper(I) acetylide plays an important role in the oxidative process. Furthermore, it has been postulated that an ct-aminovinylcopper(I) complex, the anti-Markovnikov hydroamination product of copper acetylide, is involved in the reported reaction system. Copper(I) bromide... 

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