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2005
Diastereoselective syntheses
O 0031
A Homo-Proline Tetrazole as an Improved Organocatalyst for the Asymmetric
Addition of Carbonyl Compounds to Nitro-Olefins. — The new homo32- 039 Michael
-proline tetrazole catalyst is prepared from hydroxymethyl proline in five steps. Asymmetric addition of carbonyl compounds (I) and (IV) to Michael acceptors (II) in an
optimal solvent system gives rise to enantioselective formation of adducts (III) and (V).
The nitro-Michael acceptor has less influence on the stereoselective outcome of the
reaction than the carbonyl compound. Generally, the enantioselectivities found are very
good, particularly with cyclohexanone. Interestingly, the selectivity of the reaction with
aldehyde (IVa) although consistent with the other substrates is the reverse of that found
for this case in the literature. — (MITCHELL, C. E. T.; COBB, A. J. A.; LEY*, S. V.;
Synlett 2005, 4, 611-614; Dep. Chem., Univ. Cambridge, Cambridge CB2 1EW, UK;
Eng.) — H. Hoennerscheid
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