Amine oxide, Cope elimination reaction

Amine oxides 2, which can be prepared by oxidation of amines 1, react upon heating to yield an olefin 3 and a hydroxylamine 4. This reaction is called the Cope elimination reaction,and as a synthetic method is a valuable alternative to the Hofmann degradation reaction of quaternary ammonium salts. 

Certain amine oxides, especially those derived from six-membered heterocyclic amines e.g. N-methylpiperidine oxide, that cannot go through a planar, five-membered transition state, do not undergo the Cope elimination reaction. 

A. C. Cope and E. R. Trumbull, "Olefins from Amines. The Flofmann Elimination Reaction and Amine Oxide Pyrolysis," Organic Reactions 11, 317 (1960). 

Cope elimination reactions of threo- and entf/zro-A, Ai-dimethyl-3-phenyl-2-butyl-amine oxide have been investigated using QM/MM calculations in water, THF, and DMSO.8 The aprotic solvents provided rate accelerations of up to 106-fold. It has been found that the amine oxide oxygen is the acceptor of three hydrogen bonds from water molecules for the reactant but only one or two weaker ones at the transition state. 

Pyrolysis of Amine Oxides The Cope Elimination Reaction ... 

Cope, A. C., Trumbull, E. R. Olefins from amines the Hofmann elimination reaction and amine oxide pyrolysis. Org. React. 1960,11, 317-493. 

Cope elimination reaction. Formation of an olefin and a hydroxylamine by pyrolysis of an amine oxide. 

Pyrolysis of the oxide of tertiary amine 1 yields olefin 2 and hydroxylamine 3. This olefination method is known as the Cope elimination reaction.1-3... 

As the name suggests, the reverse Cope elimination reaction involves formation of a tertiary amine oxide from a hydroxylamine and olefin.17,18 For example, reaction of N-methylhydroxylamine (49) with 2,2-diphenyl-4-pentenal (50) in ethanol at room temperature gave amine oxide 51 in 51% yield, together with the expected nitrone 52. It has been suggested the mechanism of the reverse Cope reaction could be a radical chain reaction19,20 however, more recent studies have confirmed the mechanism is analogous to the concerted Cope elimination.17... 

Amine oxides undergo a reaction similar to the Hofmann elimination reaction, called a Cope elimination reaction. In a Cope elimination reaction, a tertiary amine oxide rather than a quaternary anunonium ion undergoes elimination. The Cope elimination reaction occurs under milder conditions than does a Hofmann elimination reaction. 

Quaternary ammonium hydroxides and amine oxides undergo E2 elimination reactions known as Hofmann elimination reactions and Cope elimination reactions, respectively. In both reactions, the proton from the j8-carbon bonded to the greater number of hydrogens is removed. 

Pyrolysis of tertiary amine oxides (the Cope elimination reaction) also offers relatively mild reaction conditions (100-200 °C). Oxidation of the tertiary amine... 

There is a similar commercially available product based on related chemistry. It is a product of a process based on the oxidation of methyl-bis-tallow amine [204933-93-7]. The oxidation product of methyl-bis-tallow amine is a trialkylami-neoxide, a precursor to hydroxylamine stabilization chemistry. The trialkylami-neoxide is converted to a hydroxylamine and a long-chain olefin during the initial melt compounding of the pol5uner by a Cope elimination reaction, as shown below. 

Cope elimination reaction elimination of a proton and a hydroxyl amine from an amine oxide. 

Cope, A.C., Trumbull, E.R. (1975) Olefins from Amines The Hofmann Elimination Reaction and Amine Oxide Pyrolysis in Organic Reactions, RE Krieger Publ. Co., New York. 

Elimination. Ahphatic amine oxides having an ahphatic hydrogen P to the nitrogen form olefins and diaLkyl hydroxylamines when heated. This reaction is known as the Cope elimination (17)... 

However, when the temperature is increased to 120°C, the principal reaction is the elimination to olefin. The thermal decomposition of dimethyl dodecyl amine oxide at 125°C in a sealed system, as opposed to a vacuum used by Cope and others, produces 2-methyl-5-decyhsoxa2ohdine, dimethyl dodecyl amine, and olefin (23). The amine oxide oxidi2es XW-diaLkylhydroxylainine to the nitrone during the pyrolysis and is reduced to a tertiary amine in the process. 

Preparation of 3-vinylindole (84) via Cope elimination of N,N-diethyltrypt-amine-N-oxide has been reported [87], An alternate approach based on the Wittig reaction of the readily accessible N-phenylsulfonylindole-3-carbalde-hyde failed because cleavage of the sulfonyl protecting group easily produced an anion whose neutralization led to polymerization [86]. 

Oxidation of organonitrogen compounds is an important process from both industrial and synthetic viewpoints . N-oxides are obtained by oxidation of tertiary amines (equation 52), which in some cases may undergo further reactions like Cope elimination and Meisenheimer rearrangement . The oxygenation products of secondary amines are generally hydroxylamines, nitroxides and nitrones (equation 53), while oxidation of primary amines usually afforded oxime, nitro, nitroso derivatives and azo and azoxy compounds through coupling, as shown in Scheme 17. Product composition depends on the oxidant, catalyst and reaction conditions employed. 

Mechanism 19-5 The Cope Elimination of an Amine Oxide 908 19-16 Reactions of Amines with Nitrous Acid 910... 

Cleavage of amine oxides to produce an alkene and a hydroxylamine is called the Cope reaction or Cope elimination (not to be confused with the Cope rearrangement, 18-32). It is an alternative to 17-7 and 17-8. The reaction is usually... 

The thermal decomposition of sulfoxides whose sulfur atom is attached to the a carbons of ketones or esters leads to a,(3-unsaturated ketones or esters, respectively, via a cis elimination. The reaction is reminiscent of alkene formation by Cope elimination of dialkylhydroxylamines from tertiary amine oxides (equation 567) [321]. 

Tertiary amine oxides fragment on heating to give an alkene and an N,N-dialkyIhydroxylamine (e.g. equations 1 and 2). This reaction was studied extensively by Cope, and is commonly referred to as the Cope elimination . ... 

The dominant influence of secondary orbital interactions is apparent in the reaction of methyl cyclopenta[e]-l,2,4-triazine-3-carboxylate with enamines from 3,4-dihydronaphthalen-1 (2//)-or -2(l/f)-ones. In the case of the 3,4-dihydronaphthalen-2-amine the fused pyridine 24 is obtained directly using the 3,4-dihydronaphthalen-l-amine the dihydropyridine is isolated, but can be oxidized to give the aromatic pyridine 25 derivative via a Cope elimination.403... 

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