Olation mechanism

Gelation time of a 2000 ppm Flocon 2% NaCl solution with 90 ppm Cr(III) according to Equation 5 was 2 weeks (Table II), which is in the range of the Cr colloid gelation discussed earlier. Based on the earlier discussion, the gelation reaction of redox generated Cr(III) can also be accounted for with the olation mechanism. However it is... 

The condensation reactions occur only through the mediation of sylanol groups generated by hydrolysis. There are two main opportunities. The condensation can be carried out by oxolation or olation mechanisms. The oxolation occurs with the participation of two sylonol groups. In the course of the reaction a hydroxo ligand is exchanged for an oxo one [8] ... 

Olation mechanisms. From Livage e/ al. [8). (OH) terminology defined in text. 

Under Dakin-West reaction conditions (trifluoroacetic anhydride-MeCN/80 °C/5 h), At-methoxycarbonylproline (128 R = Me) yielded Af-methoxycarbonyl-4-trifluoro-acetyl-2,3-dihydropyrrole (129 R = Me) and none of the expected Dakin-West product, the trifluoromethyl ketone (127). A possible mechanism proposed by the authors involves initial formation of a mesoionic l,3-oxazolium-5-olate (130 R = Me), but the pathway to the iV-methoxycarbonyl-2,3-dihydropyrrole (131 R = Me) and thence the final product (129 R = Me) was unexplained. ... 

A reaction of particular interest is the photochemical rearrangement of compound 243 to 3-methyl-4(3//)-quinazolinone (246). This transformation (243 -> 246) (Scheme 10), which takes place in high yield in ethanol, has been applied to several other derivatives and is clearly analogous to the photorearrangement of pyridazinium-5-olates to 4-pyrimidones (Section in,A,6). The mechanism of the reaction is not clear. 

The triaryl compounds 290 (R = Ar) are prepared by condensation of 2-aminophenol with triarylpyrylium salts followed by treatment with alkali. The triphenyl betaine (290 R = Ph) is obtained as a purple solid, mp 165 C (decomp), which shows large thermo/solvatochromic effects. Oxidation of the betaine 290 (R = Ph) with hydrogen peroxide gives the triphenyl-pyridinium-3-olate 291 (R = Ph) (see Section III,A,2) and the pyrrole 292 (R = Ph). The mechanism of this unusual reaction has not yet been Established. 

Batori, S., Messmer, A., Timpe, H. J. Condensed as-triazines. Part XI. Photoinduced fragmentation of pyrido[2,1-f]-as-triazinium-4-olate and its benzolog. Mechanism of Curtius rearrangement. Heterocycles, 32, 649-654. 

Knorr, R. Mechanism of the Dakin-West reaction. III. Course of ring opening during the Dakin-West reaction of an oxazolium 5-olate. Chem. Ber. 1971,104, 3633-3643. 

The mechanism of olation in the solid state, proposed in Sect. VII, was confinned the fact that only cis-hydroxoaqua complexes olate was ascribed to their doubly-bridged dimeric structure. A direct conclusion from this hypothesis is that any hydroxoaqua complex that does not have such a dimeric structure, should not olate. This conclusion was confinned in two cases the only complex of this type which was known not to have a dinuclear structure (compound 21, Table 3, Ref. 29), does not olate even at 200°C and is decomposed at higher temperatures . When the dythionate counter ion in this salt was replaced by iodide, a normal, double-bridged dimer was obtained ... 

Contrary to acrylic esters or acrylonitrile, a vinyl ketone could be polymerized with aluminum (or zinc) alkyl alone in the absence of any added Lewis bases. The mechanism of polymerization of phenyl vinyl ketone(PVK) was studied by using a model initiator, ethylzinc-1,3-diphenyl-l-pentene-l-olate (ZC), which possessed the same structure (see below) as the growing chain end in zinc alkyl-initiated polymerization of PVK (12). 

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