Amine oxide pyrolysis

Amine oxide pyrolysis occurs at temperatures of 100°-150°C. The reaction can proceed at room temperature in DMSO.323 If more than one type of (3-hydrogen can attain the eclipsed conformation of the cyclic TS, a mixture of alkenes is formed. The product ratio parallels the relative stability of the competing TSs. Usually more of the /f-alkene is formed because of the larger steric interactions present in the TS leading to the Z-alkene, but the selectivity is generally not high. 

The present preparation of methylenecyclohexane is an example of an amine oxide pyrolysis. This route from amines to olefins in many cases yields pure olefins where the alternative method, the Hofmann exhaustive methylation reaction, is accompanied by some rearrangement to more stable isomeric olefins. 

Amide reduction with lithium aluminum hydride, 39, 19 Amine oxide formation, 39, 40 Amine oxide pyrolysis, 39, 41, 42 -Aminoacetanilide, 39, 1 Amino adds, synthesis of, 30, 7 2-Amino-4-anilino-6-(chloro-METHYl) -S-TRIAZINE, 38, 1 -Aminobenzaldehyde, 31, 6 hydrazone, 31, 7 oxime, 31, 7 phenylhydrazone, 31, 7 > -Aminobenzoic add, 36, 95 2-Aminobenzophenone, 32, 8 c-Aminocaproic acid, 32, 13 6-Aminocaproic acid hydrochloride,... 

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

This reaction, which is related to the well-known amine oxide pyrolysis, involves a syn elimination of the selenenic acid, but proceeds under milder conditions (20 C to 60 C instead of 400 C). It is more regioselective, takes place away from the oxygen and leads to allyl alcohols instead of enols, except when the only available hydrogen is the one a to the hydroxy group (Scheme 173, b). ... 

Table 1 Endo- vj. Exo-cyclic Elimination from Amine Oxide Pyrolysis...

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

Cram, D. J., McCarty, J. E. Stereochemistry. XXIV. The preparation and determination of configuration of the isomers of 2-amino-3-phenylbutane, and the steric course of the amine oxide pyrolysis reaction in this system. J. Am. Chem. Soc. 1954, 76, 5740-5745. 

Staurosporine (173) has been converted to the 4, 5 -alkene via amine oxide pyrolysis the alkene was hydroxylated, and also subjected to hydrobora-tion-oxidation to give regioselectively the 5 -a-alcohol. Various other subsequent manipulations at the 4 - and 5 -positions were also reported. 4 -iV-Methyl-5 -hydroxystaurosporine and 5 -hydroxystaurosporine are new in-dolocarbazoles that have been isolated from a marine Micromonospora strain. ... 

Amine oxide pyrolysis occurs under milder conditions than any of the other... 

Sol 7. In amine oxide pyrolysis, cycloelimination uses a ring of five atoms, therefore, the reaction is necessarily syn selective. The oxide of trans-l-phenyl-2-dimethylaminocyclohexane undergoes syn elimination to give... 

Amine oxide pyrolysis occurs at temperatures of 100-150°C. The reaction will proceed at room temperature for some amine oxides in dimethyl sulfoxide.If more than one type of / -hydrogen is present in the amine oxide, a mixture of olefins will generally result. The amine oxides are prepared from tertiary amines by oxidation with peroxycarboxylic acids or hydrogen peroxide. Some typical examples are shown in Section A of Scheme 7.15. 

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. 

---