The lithium perchlorate-induced ring opening of (S)-triphenylethylene oxide (3) with secondary amines (piperidine (a), N-methylpiperazine (b), N-phenylpiperazine (c) and morpholine (d)) takes place in a stereospecific and completely regioselective manner to afford (R)-2-(dialkylamino)-1,1,2-triphenylethanols (4a-d). These amino alcohols catalytically induce the addition of diethylzinc to benzaldehyde with high enantioselectivity at 0 degrees C and at room temperature. Ligand 4a, which provides the highest enantioselectivity at 0 degrees C, has been studied in the addition of Et(2)Zn to a family of 20 representative aliphatic and aromatic aldehydes 5a-t. For a 17-membered set of alpha-substituted substrates (5a-m,q-t), including ortho-, meta-, and para-substituted benzaldehydes, the naphthaldehydes, alpha,beta-unsaturated and aliphatic (cyclic and acyclic) aldehydes, the mean enantiomeric excess of the resulting alcohols 6a-m,q-t is 97%, whereas for three alpha-unsubstituted specimens (5n-p) the addition takes place with an enantioselectivity of 92-93%.

The reaction of the phenylacetylene−dicobalthexacarbonyl complex (2) with the 4-R-2-(2-diphenylphosphinophenyl)oxazolines 1 (R = Ph) and 4 (R = CH2CH2SCH3) leads to the selective formation of the chelated complexes 3 and 5, respectively. On the other hand, the tert-butyl-substituted phosphinooxazoline 6 acts as a monodentate ligand, and its reaction with several 1-alkyne-derived complexes (2,7−10) affords readily separable mixtures of the diastereomer nonchelated complexes 11a,b−15a,b. The interconversion rate between diastereomeric pairs is dependent on the steric bulk of the alkyne substituent, and neither 3 nor 5 epimerize at room temperature. The structures of both kinds of complexes have been ascertained by a combination of spectroscopical (IR, NMR), X-ray diffraction, and chiroptical methods; this has allowed the development of a practical procedure for the establishment of the absolute configuration of the chiral alkyne−dicobaltcarbonyl complexes obtained by the selective substitution of a carbon monoxide on one of the diastereotopic cobalt atoms. The intermolecular Pauson−Khand reaction of the chelated complexes 3 and 5 with norbornadiene respectively affords the (+) and (−) enantiomers of expected enone adduct 25, but in low enantiomeric excesses. Contrary to that, the tertiary amine N-oxide-promoted intermolecular Pauson−Khand reactions of nonchelated complexes 11a,b−13a,b give the corresponding norbornadiene- or norbornene-derived adducts both in high yields (85−99%) and enantioselectivities (93−97% enantiomeric excess), in what constitutes a substantial improvement over preexisting procedures for this reaction. The possibility of achieving chiral induction in the Pauson−Khand reaction of symmetrical alkynes (via the corresponding dicobaltpentacarbonyl complexes with ligand 6) has been demonstrated for the first time. An enantioselectivity mnemonic rule and a mechanistic model that explains the observed asymmetric sense of induction have been developed, and have been found to be in agreement with the results of model semiempirical molecular orbital calculations.

Enantiopure forms of alpha,alpha'-bis(trifluoromethyl)-9,10-anthracenedimethanol and the corresponding perdeuterated isotopomers were prepared. The conformational study was carried out by (1)H NMR, and the absolute configuration was determined by the X-ray study of the crystallized diastereoisomeric carbamate derivative. This compound was tested as a chiral solvating agent (CSA). The results showed very good discrimination for several racemic mixtures that improved other classical methods. The study of diastereomeric complexes was carried out by determination of the stoichiometry of the complex and the binding constant of the equilibrium.