Abstract
This article reviews the applications of cinchona alkaloids as
asymmetric catalysts. In the last few years, characterized by the
resurgence of interest in asymmetric organocatalysis, cinchona derivatives have
been shown to catalyze an outstanding array of chemical reactions,
often with remarkable stereoselectivity. This work presents an overview
of the transformations developed in the period from 2001 through
2009, highlighting applications in the synthesis of bioactive molecules
and natural products.
1 Introduction
2 Additions to Carbonyls
3 Additions to Imines
4 Conjugate Additions
5 Additions to Olefins
6 Nucleophilic Substitutions
7 Electrophilic Halogenations
8 Opening of Cyclic Anhydrides
9 Acylations
10 Cycloadditions
11 Rearrangements
12 Decarboxylations
13 Miscellaneous
14 Conclusions and Outlook
List of abbreviations: Alloc, allyloxycarbonyl;
Boc, tert -butyloxycarbonyl;
Bs, benzenesulfonyl; BTTP, tert -butyliminotri(pyrrolidino)phosphorane;
Cbz, benzyloxycarbonyl; DABCO, 1,4-diazabicyclo[2.2.2]octane;
DBAD, dibenzyl azodicarboxylate; DBU, 1,8-diazabicycloundec-7-ene;
DCE, 1,2-dichloroethane; DFT, density functional theory; DIPEA, N ,N -diisopropylethylamine;
DNP, 2,4-dinitrophenyl; DMB, 3,4-dimethoxybenzoyl; DPM, diphenylmethyl;
DTAD, di-tert -butyl azodicarboxylate; EVE,
ethyl vinyl ether; EWG, electron-withdrawing group; FBSM, 1-fluorobis(phenylsulfonyl)methane;
HFiPA, 1,1,1,3,3,3-hexafluoro-2-propyl acrylate; LAH, lithium aluminum
hydride; LG, leaving group; Moc, methyloxycarbonyl; MPEG, poly(ethylene
glycol) monomethyl ether; MS, molecular sieves; MVK, methyl vinyl
ketone; NFSI, N -fluorobenzenesulfonimide;
NMR, nuclear magnetic resonance; Ns, p -nitrophenylsulfonyl;
PEG, poly(ethylene glycol); PS, proton sponge [1,8-bis(dimethylamino)naphthalene];
rds, rate-determining step; TBAF, tetrabutylammonium fluoride; TCCA, trichloroisocyanuric
acid; TFAA, trifluoroacetic anhydride; THF, tetrahydrofuran; TMAF,
tetramethylammonium fluoride; TMS, trimethylsilyl; Ts, p -toluenesulfonyl; UNCA, urethane-protected α-amino
acid N -carboxyanhydrides.
Key words
cinchona alkaloids - organocatalysis - asymmetric
catalysis - kinetic resolution - stereoselective
synthesis