A series of publications has appeared recently which point out the formation of significant quantities of O-isomer in the alkylation of the alkali enolates of p -ketoesters and @-diketones /l-4/.
However, in the above referred works /2, 3/, the reactions were carried out with the use of carbonates or tert-butylates of alkali metals as bases. Be a result, in the resction mixtures there was always a certain amount of water or alcohol.
It seemed worthwhile to us to carry out the ethylation reaction in the absence of hydroxylic compounds, since it is well known that the latter bring about the screening of the oxygen center due to selective salvation /5, 6/.
The reactions were carried out in a dry argon atmosphere. The products were identified by means of thin-layer chronatography (A1203 IV; hexane-ethyl acetate 13:l).
Quantitative analysis of the mixtures was carried out by GLPC using a flame-ionisation detector chromatograph. The length of the column was 2 m; the diameter 4 mm; the stationary phase was polysiloxane (1%) placed on NaCl CO.15 -0.25 mm>. The column temperature was 120°C with nitrogen carrier gas flow rate at 70 ml per min.
Samples of C-ethyl compound /7/ and ethyl d,aC-dietbylacetoacetate /8/ were obtained by standard methods. , ethylp-ethoxycrotonate obtained in experiment No 1 (TALE&E 2) was freed of impurities of C-isomer and ethyl d,O(-diethylacetoacetate by means of preparative chromatography (Al.203 IV; hexaneethyl acetate 13:l). The IR-spectrum shows two strong bands at 1632 cm-l' and 1718 cm-'.
The results obtained are presented in tables 1, 2 and 3. In all cases, the yields in per cents were calculated for the ethyl acetoacetate entering in the reaction.
Practically, complete alkylation was achieved in the experiments with (EtO)2S02 and EtI.