Aerobic oxidative amination

The synthesis of N phthaloyl enamides has been reported by a remarkably general method for aerobic oxidative amination of unactivated alkyl olefins as shown in Scheme 9.6 [12]. From a practical synthesis point of view, the phthalimide can not only serve as a directing group for asymmetric hydrogenation but can also be removed under mild conditions. 

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. 

Synthesis of 2-Hetarylquinazolin-4(3 -ones. The title compound has been employed in an efficient method for the synthesis of 2-hetarylquinazolin-4(3/f)-ones via a copper-catalyzed aerobic oxidative amination protocol (eq 16). ... 

Liu G, Yin G, Wu L (2008) Palladium-catalyzed intermolecular aerobic oxidative amination... 

Liu and coworkers reported a base-modulated regioselective Pd-catalyzed intramolecular aerobic oxidative amination of alkenes for five- or seven-memberedring products by varying the reaction conditions [12]. 

Finally, C—N bond formation has been also accomplished through aerobic oxidative amination of arylboronic acids (Evans-Chan-Lam coupling) under poly-NHC-copper(II) catalysis. In particular, azoles and aromatic amines were successfully coupled with arylboronic acid using catalyst 73, with catalytic efficiencies comparable to those of other previously reported copper(II)-based catalytic systems for this reaction. 

C) Direct O2 aerobic oxidative amination of styrene with Pd(OAc) Et2N... 

It was also reported by PruP et al. [31] that in situ formed cobalt(III) complexes of pyridine-4-ylmethyl-propyl-amine (PYPA) on preformed organomodified HMS are active as catalysts in the aerobic oxidation of styrene and also 1-decene (Figure 3). Incorporation of PYPA may be achieved by following several routes viz. sol-gel synthesis, post modification of sol-gel AMP-HMS, and grafting. The authors proposed that all materials are able to act as... 

Another argument against the oxo-transfer mechanism in our catalytic aerobic oxidation protocol is the lack of formation of sulfoxides from sulfides, N-oxydes from amines and phosphine oxydes from phosphines. Alkenes also proved to be inert towards oxidation no epoxide formation could be detected under our reaction conditions. 

James et al. reported that aerobic oxidation of primary amines in the presence of a ruthenium porphyrin complex Ru(TMP)(0)2 (TMP = tetramesitylporphyrinato) gives nitriles (100%) (Eq. 3.31) [66]. 

Heterogeneous catalysts such as hydroxyapatite-bound Ru complex [67] and Ru/ AI2O3 [68] can be also used for the aerobic oxidation of primary amines to nitriles (Eqs. 3.32 and 3.33). 

Recently, a new type of reaction - that is, aerobic oxidative cyanation of tertiary amines - was discovered. In this reaction, oxidation with molecular oxygen in place of peroxides, in addition to direct carbon-carbon bond formation by trapping of the iminium ion intermediates with a carbon nucleophile under oxidative conditions, is accomplished simultaneously. The ruthenium-catalyzed oxidation of tertiary amines with molecular oxygen (1 atom) in the presence of sodium cyanide gives the corresponding a-aminonitriles (Eq. 3.74) [132], which are useful for synthesis of a-amino acids and 1,2-diamines. 

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). 

Newmann R, Levin M (1991) Selective aerobic oxidative dehydrogenation of alcohols and amines catalyzed by a supported molybdenum-vanadium heteiopolyanion salt. J Oig Chem 56 5707-5710... 

Very recently, Liu and coworkers reported a palladium-catalyzed intramolecular aerobic oxidative allylic amination of unactivated alkenes [34]. The reaction of 22... 

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. ... 

A similar reaction was reported by Meth-Cohn and Suschitzky [62], who obtained aldehydes from the aerobic oxidation of amines in neutral solution in the presence of a manganese dioxide catalyst. 

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