Heterogén katalitikus enantioszelektív hidrogénezés mechanizmusa. = Mechanism of enantioselective heterogeneous catalysed hydrogenation.

Piroszőlősav etileszter enantioszelektiv hidrogenezeset vizsgaltuk Pt-alfa- es beta-izocinkonin katalizatorral. Ecetsavban az alfa-izocinkonin eseten 93-94 %, beta-izocinkonin eseten 70-72 % ee-t ertunk el. Toluolban a beta-izocinkonin eseten az enantioszeletivitas iranya megfordult. Vizsgalatuk aril-trifluormetil ketonok es trifluormetil-ciklohexil keton enantioszelektiv hidrogenezeset Pt-cinkonidin katalizatorral. Trifluorecetsav adalek jelenleteben az enantioszelektivitas megnő. Az oldoszertől fuggően az enantioszelekcio iranya valtozott. Elsőkent sikerult enol esztert (2-acetoxiakrilsav etil esztert) 50-60 % enantioszelektivitassal hidrogenezni. Alfa-ketoeszter funkciot tartalmazo szteroid (3-acetoxi-23-ketolitokolsav metileszter) ketocsoportjat 78 %-os enantioszelektivitassal sikerult hidrogenezni. Fenilglioxilsav eszterek enantioszelektiv hidrogenezeset vizsgaltuk. Pt-cinkonidin eseten jo enantioszelektivitast talaltunk, mig Pt-beta-izocinkonin eseten az enantioszelekcio inverziojat eszleltuk toluolban. Vizsgalatokat vegeztunk a vinil oldallancon atalakitott cinkonidinokkal.. Az uj vegyuletek a piroszőlősav etil eszter enantioszelektiv hidrogenezeseben a cinkonidinhez hasonlo eredmenyeket adtak. Vizsgaltuk Pt-C9-O-szubsztitualt cinkona alkaloid (eterek es eszterek) katalizator hatasat piroszőlősav etileszter enantioszelektiv hidrogenezeseben. Az enantioszelektivitas viszonylag alacsony ertekű nagy terkitoltesű C9-O-szubsztituens eseten es iranya sokszor elterő a varttol. | The enantioselective hydrogenation of ethyl pyruvate was studied on Pt-alumina catalysts modified by alfa- and beta-isocinchonine. In the case of beta-isocinchonine an inversion of enantioselectivity was observed. The enantioselective hydrogenation of aryl-trifluoromethyl ketones and trifluoro-methylcyclohexyl ketone on Pt-cinchonidine catalyst has been investigated. The achieved ee was 67-85% and 48%.Depending on solvents the inversion of enantioselectivity was observed. We used the Pt- and Pd-cinchonidine systems succesfully for the asymmetric hydrogenation of an enol esters. The oxo function of methyl 3alfa-acetoxy-23-oxo-5beta-cholan-24-oate was hydrogenated with 78% enantioselection over Pt-cinchonidine catalyst . Enantioselective hydrogenation of phenylglyoxylic acid esters was investigated.The formation of R-mandelic acid esters was 79-94% with Pt-cinchonidine. On Pt-beta-isocinchonine catalyst inversion of enantioselectivity occured. The enantioselective hydrogenation of ethyl pyruvate was studied on Pt catalysts modified by C3-modified cinchonidine. The achieved ee was similar to that of parent cinchonidine (79-91%). The effect of the structure of C9-O-substituted cinchona alkaloids (ethers and esters) on the enantioselectivity of the Pt-alumina-catalyzed hydrogenation of ethyl pyruvate was investigated.The ee values observed were still low and even opposite to that expected. The inversion of enantioselectivity can explain by tilted adsorption of chiral modifiers.