Spontaneous rearrangement reaction

Between these two extremes of spontaneous rearrangement and total failure to rearrange, Braverman and Stabinsky36-38 have observed intermediate behavior. The reaction of crotyl alcohol with C13CSC1 afforded an equilibrium mixture of both crotyl trichlormethanesulfenate (13) and a-methylallyl trichloromethyl sulfoxide (14, equation 9). 

The lH-l,2,4-triazole compounds possess important pharmacological activities such as antifimgal and antiviral activities [18-20]. In the present study, the reactive intermediates 45a-c, prepared in situ from the dichlorides 44a-c, were reacted via the cycloaddition reaction with ethyl cyanoacetate 40 to give, after spontaneous rearrangement, the triazole hydrazides 41a-c. These compoimds were used as starting materials for the synthesis of the... 

A potential undesirable effect of DCC coupling reactions is the spontaneous rearrangement of the o-acylisourea to an inactive N-acylurea (Stewart and Young, 1984) (Figure 3.6). The rate of this rearrangement is dramatically increased in aprotic organic solvents, such as DMF. 

The reaction of 2-substituted-5-aroyl-isothiazol-3-ones (214) with hy-droxylamine or arylhydrazines gives the 1,2,5-oxathiazoles 216 (Z = O) or 1,2,3-thiadiazoles 216 (Z = NAr ), as a result of a spontaneous rearrangement of unisolated oximes 215 (Z = O) or arylhydrazones 215... 

The second arm of the scheme involves first a reaction of the (3-beta ketoester (7-1) with nitrous acid. The first product from nitrosation on the activated carbon spontaneously rearranges to afford oxime (7-2). Treatment with acetyl chloride then affords the (9-acylated oxime (7-3). Condensation of that compound with the imino ether from propionitrile leads to the formation of the imidazole (7-4). 

The thermal ring closure reaction of a 1,3,5-triene to a 1,3-cyclohexadiene occurs by a concerted disrotatory electrocyclic mechanism. An example of the latter is the oxepin-benzene oxide equilibrium (7) which favors the oxepin tautomer at higher temperatures (Section 5.17.1.2). Oxepin (7) was found to rearrange to phenol during attempted distillation at normal pressure (67AG(E)385>. This aromatization reaction may be considered as a spontaneous rearrangement of the oxirane ring to the dienone isomer followed by enolization (equation 7). 

Section IV,A,1 Attempts to prepare spiro-3i/-pyrazoIes from esters of 6-diazopenicillinic acid and l-phenyI-2-propyn-l-one resulted in spontaneous rearrangement to the isomeric l//-pyrazoIes via a unique migration of the 0-Iactam 6-7 bond.174 A similar spontaneous acyl migration was observed in the reaction between a 3-diazothiolan-4-one and DMAD.175... 

All aminochromes undergo a slow spontaneous rearrangement in aqueous solution, although the rate is considerably affected by the structure of the aminochrome in question. The rearrangement of all aminochromes is however markedly catalyzed by alkali (see ref. 3 for early references). The structure of the fluorescent alkaline rearrangement product of adrenochrome was not ascertained until 30 years after the characteristic fluorescence reaction had been first reported,138 and the substance [i.e. adrenolutin, 5,6-dihydroxy-V-methylindoxyl (31), often formulated as 3,5,6-trihydroxy-V-methyl-indole (32), cf. refs. 3, 108] was finally isolated in crystalline form in 1949.139,140 Subsequently, A-ethyl-5,6-dihydroxyindoxyl (33) and... 

In some thermolysis reactions, amines (90 and 91) have been characterized.108,111,112,457 When R1 = CH2OH and R2 = H in Scheme 164, the aziridine undergoes spontaneous rearrangement (Scheme 166).125 An endo-triazoline adduct from norbornene yields a polymer as the principal... 

Presumably, a new kind of rearrangement process takes place in the reaction of dicyclopentadienyltungsten dichloride with tris(trimethylsilyl)silyllithium (equation 3473). Silyl complexes formed as intermediates spontaneously rearrange with formation of silylcyclopentadienyl complexes, but the mechanism of this process is not yet clear. 

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