Hofmann degradation pathway

In media of low proton availability (MeCN, dmf, hmpa)762, ylide formation was found and products derived from the radical cleavage of the phosphonium ion have been observed. The initial cation would interfere in the reaction process as an acid. A competition can exist between the one-electron pathway (dimerization, disproportionation of R ) and the two-electron pathway (ylide formation, Hofmann degradation, phosphine oxide formation) (Table 24). 

A reaction pathway important for the structure elucidation of oncinotine and neooncinotine is the acid-catalyzed opening of the lactam ring to the amino acid, which, following esterification with methanolic HC1, is acety-lated and the basic tertiary nitrogen atom methylated with CH3I. The thus-formed quaternary ester acetate mixture of 43 and 44 (as the fluorides) is then pyrolyzed, whereby a Hofmann degradation reaction occurs to form the three compounds 45, 46, and 47, shown in Scheme 6. 

An unexpected rearrangement of compound (48), obtainable by oxidation of lycoctonine followed by pinacolic dehydration and Curtius or Hofmann degradation has been observed. Treatment of this primary amine with nitrous acid affords two products (49) and (50) pathways for their formation have... 

However, it was suggested that if the residual anions could be completely removed from the organoclays, the primary degradation pathway would switch to an elimination-type mechanism [16]. The Hofmann elimination of ammonium compounds was most probably the source of additional amounts of vinyl-type unsaturation found in melt-processed OMMT-PE relative to both the polymer control and the Na+MMT-PE samples [28]. On the other hand, the presence of alkenes was also explained by three possible routes of decomposition (i) pyrolysis of alkanes derived from the major component of the organic part, i.e., hydrogenated tallow (HT) (ii) pyrolysis of the tallow (unsaturated fatty acids used for the preparation of the quaternary ammonium salt) and (iii) decarboxylation of RCOO and RCO radicals [17, 29]. 

Two mechanisms of degradation are proposed for organoclays with ammonium surfactants. First is the elimination-type mechanism (Hofmann elimination), which is assumed to be primary degradation pathway if the salt anions are completely removed from the organoclay, and second is nucleophilic substitution with an attack of residual anions. 

The most common degradative pathway is through quatemization of the basic nitrogen followed by Hofmann elimination to furnish a phenanthrene possessing a i3-dimethylaminoethyl side chain. Such a phenanthrene alkaloid can then suffer... 

Cisatracurium and atracurium share the same metabolic pathways, but Hofmann elimination may have a greater role in the elimination of cisatracurium than in atracurium (2,4-7). Spontaneous in vivo degradation accounts for 77 % of total body clearance of cisatracurium (6). Organ clearance is 23% of total body clearance. Major metabolites of cisatracurium are laudanosine and a monoquaternary acrylate. 

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