Amines oxidation with manganese

Enhancing the utility of the allq lation-rearrangenient sequence in synthesis, the Evans group addressed the problems of a-versus-y alkylation as well as low anion reactivity by employing heterocyclic sulfides as the alleviation substrates tScheme IR.IfiE For instance, allylic imidazolyl sulfide 56 could be allqvlated efficiently, reaction at the a-position being favored by a chelated but reactive allyl lithium intermediate. Oxidation of 57 to the allylic sulfoxide and treatment with a secondary amine thiophile provided allylic alcohol 58 in high yield and with excellent stereoselectivity at the trisubstituted alkene. Allylic oxidation with manganese dioxide completed a synthesis of the sesquiterpene nuciferal (59). ... 

Oxidations with manganese dioxide Azomethines from sec. amines... 

Step 1. Extraction of the acid soluble fraction (i.e., carbonates) with CH3COOH Step 2. Extraction of the reducible fraction (i.e., iron/manganese oxides) with hydroxyl amine hydrochloride... 

The selective oxidation of a secondary alcohol in the presence of a tertiary amine function has been carried out with manganese dioxide (equations 43 and 44) in the context of an alkaloid synthesis. ... 

Tertiary amines containing a methyl group bound to carbon are oxidized to formamides. Dimethylaniline gives A-methylformanilide in 78% yield on treatment with manganese dioxide in chloroform for 18 h at room temperature [826]. Other reagents for this purpose are potassium permanganate in acetone and acetic acid at room temperature (yields 67-82%)... 

Like tertiary amines, tertiary phosphines are readily transformed into the corresponding oxides, phosphine oxides. Tributylphosphine in di-chloromethane is oxidized with ozone adsorbed on silica gel at -70 "C to tributylphosphine oxide in 92% yield [113]. Other oxidants used to transform phosphines into phosphine oxides are potassium peroxysulfate [205], argentic oxide [381 ], manganese dioxide [813], and barium manganate [S55] (equation 537). 

The oxidation of aldehydes in the presence of amines occurs at low temperatures with nickel perox-ide. Similarly, the oxidation of aromatic aldehydes with manganese dioxide or ruthenium chloride in the presence of sodium cyanide and an amine leads to the corresponding amides. 

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