Interaction of 1-acetyl-2-phenyl-5-hydroxy-pyrazolidines withβ-substituted esters on the surface of adsorbents

Abstract

The interaction of 1-acetyl-2-phenyl-5- We showed previously that the hydroxyl group of 5-hydroxypyrazolidines (I) readily undergoes nucleophilic substitution [1], including that in reactions with ketones as the C-nucleophiles. In accomplishing the last conversion, the application of an unusual method for carrying out the process --in the adsorbed state without a solvent [2], not requiring preliminary activation of the CH-acid --was shown to be very successful. The adsorbent aluminum oxide, employed by us in reactions with ketones and being one of the most common for surface reactions [3], showed unsatisfactory results in the synthesis of derivatives of the esters (II), whereby the reactions had a poor yield or, for example in the case of cyanacetic ester, did not proceed at all [2]. The search, undertaken by us in the present work, for the best conditions in the synthesis of the derivatives (II) showed that there is no universal adsorbent to perform reactions of the pyrazolidines (I) with CH-acid compounds: the individual search for optimal conditions of the adsorbent and the temperature was undertaken in practically every case. Moreover, we showed that the irradiation of the reaction mixture in a microwave oven instead of the usual heating was found to be effective in some cases. The reaction time was thereby shortened in all cases, and the composition of the reaction mixture was changed in the reaction of the pyrazolidine (Ib) with carbethoxycyclopentanone. The optimal reaction conditions found as well as the characteristics of the compounds synthesized are presented in Table 1. , is an s-substituted fl-ketoester having the capability of keto-enol tautomerism. The spectral data for compound (Ha) (see Tables 1-3), which we synthesized on the surface of polyamide, confirmed its identity with the sample obtained on aluminum oxide. In the same way as previously [2], the spectral characteristics only indicate the presence of the ketonic tautomer --the IR spectrum of the solution in CCI 4 does not contain absorption bands of the enol isomer. According to the data of [2], compound 0la) has the

Diastereoselective reductive amination of pyrazolidinyl alkyl ketones

“…The diastereomer was identified as 1-acetyl-3S-[2S-(1S-phenylethylamino)propyl]-5R-methyl-2-phenylpyrazolidine. Bond lengths and valence angles for the heterocycle were close to those for previously studied pyrazolidine derivatives [11,12] (2). Atoms N(1) and N(2) in their turn are significantly pyramidalized (sums of valence angles were 332.4 and 356.1°) with clearly expressed flattening of the first due to its conjugation with the acetyl fragment.…”