?url_ver=Z39.88-2004&rft_id=3105641&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=https%3A%2F%2Fdoktori.bibl.u-szeged.hu%2Fid%2Feprint%2F2879%2F&rft.title=Asymmetric+cascade+reaction+of+2-nitrophenylpyruvates+over+chirally+modified+platinum+catalyst&rft.creator=+Kov%C3%A1cs+Lenke&rft.subject=01.04.+K%C3%A9miai+tudom%C3%A1nyok&rft.description=We+developed+the+first+heterogeneous+catalytic+asymmetric+cascade+reaction+for+the+efficient+synthesis+of+hydroquinolone+derivatives+starting+from+2-nitrophenylpyruvates+using+supported+Pt+catalysts+modified+by+cinchona+alkaloids%2C+in+which+we+obtained+high+yields+and+good+enantioselectivities.+It+was+shown+that+the+cascade+leading+to+these+products+started+with+the+enantioselective+hydrogenation+of+the+activated+keto+group%2C+followed+by+the+reduction+of+the+nitro+group+and+finally+the+intramolecular+amidation%2C+all+steps+occurring+on+the+Pt+surface.+We+found+that+tuning+the+reaction+conditions+has+a+major+influence+on+the+product+composition%2C+as+the+enantioselective+hydrogenation+and+the+reduction+of+the+nitro+group+are+competing+reactions.+Substituents+on+the+aromatic+ring+have+important+influence+on+the+hydroquinolone+yields%2C+which+was+explained+by+their+effect+on+the+reduction+rate+of+the+nitro+group.+It+was+demonstrated%2C+that+the+final+cyclization+step+of+the+cascade+reaction+occurs+on+the+catalyst%2C+i.e.+metal+surface.%0D%0AWe+have+investigated+the+possibility+of+carrying+out+the+reaction+in+continuous-flow+hydrogenation+system.+However%2C+the+high+selectivities+and+enantioselectivities+of+the+main+(R)-3-hydroxy-3%2C4-dihydroquinolin-2(1H)-one+products+obtained+in+batch+reactor+were+not+achieved%2C+due+to+perturbed+rate+balance+of+the+first+two+competitive+steps.+Pre-modification+of+the+Pt%2FAl2O3+catalyst+with+the+cinchona+modifier+enhanced+the+product+selectivity%2C+whereas+recirculation+of+the+product+mixture+besides+increasing+the+conversion+and+selectivity%2C+didn%E2%80%99t+cause+a+drastic+change+in+ee.%0D%0AFinally%2C+the+heterogeneous+cascade+reaction+disclosed+here+is+a+novel+application+of+the+Orito+reaction+and+could+also+be+a+starting+point+for+developing+attractive+strategies+for+the+synthesis+of+various+optically+pure+N-heterocyclic+compounds.%0D%0A&rft.date=2016-05-17&rft.type=Disszert%C3%A1ci%C3%B3&rft.type=NonPeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=https%3A%2F%2Fdoktori.bibl.u-szeged.hu%2Fid%2Feprint%2F2879%2F1%2FDisszertacio_veg_jav%25C3%25ADtott.pdf&rft.format=application%2Fpdf&rft.language=en&rft.identifier=https%3A%2F%2Fdoktori.bibl.u-szeged.hu%2Fid%2Feprint%2F2879%2F10%2FTezisEnglishKovacsLenke.pdf&rft.format=application%2Fpdf&rft.language=hu&rft.identifier=https%3A%2F%2Fdoktori.bibl.u-szeged.hu%2Fid%2Feprint%2F2879%2F9%2FTezismagyarKovacsLenke.pdf&rft.identifier=+++Kov%C3%A1cs+Lenke%0A+++Asymmetric+cascade+reaction+of+2-nitrophenylpyruvates+over+chirally+modified+platinum+catalyst.%0A++Doktori+%C3%A9rtekez%C3%A9s%2C+Szegedi+Tudom%C3%A1nyegyetem+(2000-).+%0A(2016)++++(K%C3%A9ziratban)++&rft.relation=3105641&rft.identifier=3105641&rft.language=eng