Ketones spectroscopic analysis

The acylation of enamines derived from cyclic ketones, which can lead to the acyl ketone or ring expansion (692-694), was studied by NMR and mass spectroscopic analysis of the products (695,696). In a comparative study of the rates of diphenylketene addition to olefins, a pronounced activation was observed in enamines (697). Enamine N- and C-acylation products were obtained from reactions of Schiff s bases (698), vinylogous urethanes (699), cyanamides (699), amides (670,700), and 2-benzylidene-3-methylbenzothiazoline (672) with acid chlorides, anhydrides, and dithio-esters (699). 

For the final part (Scheme 5.3), the 20-carbon chain of fumonisin Bj was coupled from the Uthium acetylide derived from 273 and the Weinreb amide 279 (233). After enantioselective reduction of the alkynyl ketone 281 (234, 235), the C-10 stereochemistiy was set, followed by benzyl ether formation and acid-catalyzed acetonide removal, to provide diol 282 (236). Using tricarballylic acid dibenzyl ester, the two hydroxy groups were esterified (237) and the hydrogenation of the azide, the alkyne, and the benzylic ethers led to the target product, fumonisin Bj (249). The spectroscopic analysis matched with those of commercial fumonisin Bj and further experiments on the synthetic material showed inhibitoiy activity on sphingoUpid biosynthesis. 

In the old days, before spectroscopic analysis became routine, this reaction, when carried out with iodine (X = I), was used as a qualitative visual test for methyl ketones because the iodoform (CHI3) produced is easily recognizable as a pale yellow solid. Nowadays, the reaction is used mainly as a means of shortening the carbon chain of a methyl ketone. The mechanism involves repeated generation of a terminal enolate from the methyl ketone and its reaction with HOX, a weak acid and the putative halogenating agent under the reaction conditions ... 

The potential of UV-Vis derivative spectroscopy has not been fully exploited. Much of the spectroscopic analysis of aromatic compounds concerns the precise location of shoulders and maxima of hidden bands, a task ideally suited for derivative spectroscopy. The higher order derivative spectra can provide a fingerprint analysis that can distinguish compounds with the same chromophore, such as ketones (266). Isomeric compounds, such as o- and /7-xylene, which cannot be differentiated by their zero-order spectra, can be quantitatively analyzed in higher order spectra (375). The technique of differential second-derivative UV (SEDUV)... 

Jatrophone (LXXV) a new diterpenoid ketone of novel structure, which possesses tumour inhibitory properties, has been isolated from Jatropha gossypiifolia. Its structure has been determined by spectroscopic analysis of... 

A set of neutral mononuclear rhodium(i) complexes of the P-NH ligands were also prepared by the reaction of [Rh(cod)Cl]2 with an allqrl-substituted phenylaminophosphine (Scheme 9). The structures of the new complexes were elucidated by spectroscopic analysis. The complexes were applied to the transfer hydrogenation of acetophenone derivatives and aryl alkyl ketones in the presence of 2-propanol. Particularly, complex 35b behaved as an excellent catalyst, giving the corresponding alcohols with conversions of up to 99%. 

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