Studies on the oxidation of enamines with molecular oxygen. I. Oxidation of Some Piperidino Alkenes

Abstract

In the autoxidation of 1‐piperidinocyclohex‐1‐ene (1), 1‐piperidinobut‐1‐ene (2), 3‐piperidinopent‐2‐ene (3), and 1‐piperidino‐2‐methyl‐prop‐1‐ene(4) only products of an oxidative attack at the CC‐double bond are formed. Both α‐aminoketones, the products of the rearrangement of primarily formed epoxides, and products of the oxidative session of the CC double bond are obtained. As a side reaction some hydrolysis of the starting enamines takes place. This hydrolysis proves that some water must be formed during the enamine oxidation.

Silylene and Germylene Intermediates in the Reactions of Silole and Germole Dianions with N,N′‐Di‐tert‐butylethylenediimine

“…Evidently 15 arises via C-oxidation of spirocyclo-enediamine 3 (Scheme 8). Similar oxidation of enamines, enhanced in presence of molecular sieves was described previously by Blau et al [17][18][19] Eur (15) shown with 50 % probability thermal ellipsoids. The germanium-nitrogen bond in 3b (E = Ge) is less stable than a silicon-nitrogen bond and rapidly decomposes in the presence of air to give the cyclo-trigermoletrioxane 16 (Scheme 8), identified by X-ray crystallography and 1 H, and 13 C NMR analysis.…”

Synthesis of 2, 5‐Diamino‐p—benzoquinones via Aerobic Oxidative C(sp2)‐C(sp2) Bond Cleavage and Mechanistic Studies

“…In acidic conditions, I can tautomerize to generate its enamine ketonic form I′ , which is expected to be more reactive to oxygen due to the presence of an exocyclic CC double bond on a non‐aromatic ring. It is well‐known that activated olefinic units react with ground state molecular oxygen ( 3 O 2 ) by a free radical mechanism . Accordingly, enamine I′ oxidation by molecular oxygen ( 3 O 2 ) is probed using DFT calculations.…”

Intramolecular 1,3-dipolar cycloadditions of dihydroimidazolium ylides: synthesis of pyrrolo[1,2,3-de]quinoxalines and imidazo[1,2-a]indoles

“…Indeed, the oxidation of enamine systems by means of molecular oxygen has been reported in the literature. [36][37][38] Presumably, the presence of adventitious molecular oxygen, perhaps originating from undegassed solvents, is the cause of this oxidation process. The reason for different outcomes for the alkyl and aryl bromoketones is unclear but may be due to stabilisation of 17 through conjugation of the double bond with the 3-aryl system.…”