Emde degradation / reduction

Several syntheses of secoquettamines have been performed. Seco compounds 234 and 235 were semisynthesized from quettamine (236) by Hofmann and Emde degradations, respectively (179). Chattopadhyay and Shamma (184) conducted a total synthesis of these bases with the intermediacy of quettamine (236) (Scheme 36). In this approach Reissert compound 237 served as substrate. On reaction with 4-benzyloxybenzaldehyde 237 supplied the addition product 238, which after N-methylation and sodium borohydride reduction afforded amino carbinol 239. Compound 239 was cyclized to... 

EMDE DEGRADATION. Modification of the Hofmann degradation method for reductive cleavage of the carbon-nitrogen bond by treatment of an alcoholic or aqueous solution of a quaternary ammonium halide with sodium amalgam. Also used as a catalytic method with palladium and platinum catalysts. The method succeeds with ring compounds not degraded by the Hofmann procedure. 

The reductive cleavage of quaternary ammonium salts to give a tertiary amine and a hydrocarbon by reaction with sodium amalgam in hydroxylic solvents is called the Emde degradation. However, saturated hydrocarbons are not cleaved under these conditions. Grovenstein suggested that the reason for this unreactivity is due to the fact that the sodium reacts with the alcohol much faster than with the ammonium salts. However, by operating in dioxane or dioxane-alcohol mixtures, the dealkylation reaction could be accomplished. The products of the decomposition of either tetramethylammonium chloride or bromide are methane, ethylene, trimethylamine, and dimethylethylamine. 

The structure of corynoloxine (242), from Corydalis incisa, is a further example of the rare and interesting 13-methylbenzophenanthridine alkaloids.232,233 Emde degradation of corynoloxine methiodide gave both theoretically possible products (243) and (244). Catalytic reduction of either base gave the same neutral derivative (245).232 Lithium aluminium hydride reduction of (242) gave coryno line (246), an alkaloid previously isolated from the same plant species. The same tetracyclic compound (245) was obtained by a three-reaction sequence [quater-nization with methyl iodide, Emde degradation to (247), and basic hydrolysis]... 

Cryptopine (I) reacts with methyl sulfate yielding a methosulfate, B MeaS04, which when reduced with sodium amalgam in acid solution undergoes an Emde degradation as well as a reduction of the ketonic group yielding tetrahydromethylcryptopine (II), which on dehydration with... 

A second Emde reduction on the quaternary salt of methylvomicine-I cleaved ring E, trimethylamine being liberated from the resulting product by a Hofmann degradation. 

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