Cope amine oxide decomposition

We repeated Aston and Parker s preparation. The compound does indeed have the structure claimed and is quite stable, requiring hours at 180 to effect decomposition. We have also prepared di-cumyldiazene N-oxide, J., and compared it with the corresponding diazene. Decomposition of 1, like AlBN-0, is very slow. The products of decomposition are o<-methylstyrene, water, dinitrogen, and a small amount of cumyl alcohol. Nitrous oxide is not a product, and decomposition clearly is not proceeding by the process shown in eq. 4. The decomposition is most simply understood in terms of a cyclic decomposition, eq. 5, related to the Cope amine oxide decomposition (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. 

The purpose of preparing aliphatic amine oxides is usually their thermal decomposition to cis alkenes and N,N-dialkylhydroxylamines (Cope rearrangement) [156, 161, 1187]. Thus A, A -dimethylcyclohexylmethylamine is oxidized with 30% hydrogen peroxide in methanol to its oxide, whose decomposition at 90-100 °C at 10 mm of Hg and at 160 °C for 2 h furnishes 79-88% of methylenecyclohexane and 78-90% of A, A -dimethylhydroxyl-amine [161], Another example is the preparation of cw-cyclooctene from dimethylcyclooctylamine (equation 502) [1187]. 

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]. 

Although a few examples of the pyrolytic decomposition of amine oxides can be found in the early literature, the synthetic and mechanistic importance of the reaction was first recognized by Cope and co-workers.1 They showed that amine oxide 4 smoothly decomposed at 85-115 °C to styrene (5) and dimethyl hydroxylamine (6). 

The orientational behaviour of amine oxide pyrolyses has been adequately summarised by Cope and TrumbulE . As for the acetate decompositions, orientation in the simple alkyl systems is controlled primarily by statistical factors but departure from this influence is noted with the bulky r-butyl substituent and the acid strengthening beta phenyl substituents Eclipsing effects are greater in the planar five-membered transition states than in the puckered six systems and this is borne out by the greater preference for trans-olefin formation from amine oxides than esters and xanthates (152, cf. 149). 

When an amine oxide with at least one j8-hydrogen is heated, it undergoes thermal decomposition to form an alkene and an N,N-dialkylhydroxylamine. Thermal decomposition of an amine oxide to an alkene is known as a Cope elimination after its discoverer Arthur C. Cope of the Massachusetts Institute of Technology. 

Although first observed in 1898 , the thermal decomposition of tertiary amine oxides to give an alkene and hydroxylamine has received serious attention only since 1949 when the first of a series of papers by Cope and coworkers appeared . The reaction has found use in the synthesis of alkenes (equation 37), where high... 

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