Ring cleavage, hydrolytic

The mechanism for the conversion of the A -oxide (94) to the o-methylaminophenylquinoxaline (96) involves an initial protonation of the A -oxide function. This enhances the electrophilic reactivity of the a-carbon atom which then effects an intramolecular electrophilic substitution at an ortho position of the anilide ring to give the spiro-lactam (98). Hydrolytic ring cleavage of (98) gives the acid (99), which undergoes ready dehydration and decarboxylation to (96), the availability of the cyclic transition state facilitating these processes. ... 

Hofmann KW, H-J Knackmuss, G Heiss (2004) Nitrite elimination and hydrolytic ring cleavage in 2,4,6-trinitrophenol (picric acid) degradation. Appl Environ Microbiol 70 2854-2860. 

Completely different results from those obtained in the photooxidation of 2.4.6-tri-tert-butyl-X phosphorin 24 (p. 54) are obtained in the photooxidation of 1.1-dimethoxy-2.4.6-tri-tert-butyl-X -phosphorin 183, as Schaffer has found. In this case the 2-hydroxy-endoxy-phosphinic acid methyl ester 213 can be isolated in about 20% yield. Its formation can be explained by assuming normal 1.4-addition to 212 as the primary product which is transformed to 213 by hydrolytic ring cleavage of the peroxide bridge, followed by loss of methanol. 

Hydrolytic ring cleavage and analogous transformations with alcohols, amines, hydrazine, and hydroxylamine derivatives are now considered. Other ring openings have been treated in Section V,D. 

Polyaza rings suffer complete hydrolytic ring cleavage. Monocyclic 1,2,3-triazines are hydrolyzed by acid to yield 1,3-dicarbonyl compounds (Scheme 15). 1,2,3-Benzotriazines are easily converted into derivatives of 2-aminobenzaldehyde. 1,2,4,5-Tetrazines (180) are hydrolyzed with a base to give aldehyde hydrazones, RCH = NNHCOR. 

Type D Syntheses [CNCSN].— The condensation of N-chloro-amidines (76) and potassium methyl cyanoiminodithiocarbonate (77) in chloroform below 5 C yields 2-imidoyl-3-imino-5-methylthio-A -l,2,4-thiadiazolines (78) in one stage. The reductive and hydrolytic ring cleavage of the products was briefly outlined. ... 

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