An unusual electronic effect of an aromatic-F in phase-transfer catalysts derived from cinchona-alkaloid.
[structure: see text] Various N-benzylcinchonidinium salts were prepared to study electronic factors in the catalytic enantioselective phase-transfer alkylation of glycine anion equivalent. An ortho-fluoro substituent on the benzyl group in the quaternary ammonium salt dramatically increased the enantioselectivity in the alkylation. O(9)-Allyl-N-2',3',4'-trifluorobenzylhydrocinchonidinium bromide (27), which gave the highest enantioselectivity of the catalysts studied, was used to prepare 12 alpha-alkylated amino acid derivatives in 94 approximately >99% ee.
Jew
Sang-Sup
SS
College of Pharmacy, Seoul National University, Seoul 151-742, Korea. ssjew@plaza.snu.ac.kr
Yoo
Mi-Sook
MS
Jeong
Byeong-Seon
BS
Park
Il Yeong
IY
Park
Hyeung-Geun
HG
D000478:Alkylation; D000596:Amino Acids / Q000138:chemical synthesis* / Q000737:chemistry*; D001965:Bromides / Q000737:chemistry*; D002384:Catalysis; D002930:Cinchona Alkaloids / Q000737:chemistry*; D004563:Electrochemistry; D004583:Electrons; D005998:Glycine / Q000737:chemistry*; D008968:Molecular Conformation; D015394:Molecular Structure; D013237:Stereoisomerism
D000596:Amino Acids; D001965:Bromides; D002930:Cinchona Alkaloids; D005998:Glycine