Direct aldol reactions of tropinone and granatanone (pseudopelletierine) with aromatic aldehydes were promoted by the presence of water. The anti–syn-diastereoselectivity depended on the amount of water used or on the possibility of product precipitation from the reaction mixture. Some of the reactions showed excellent atom economy, a low E factor, and high diastereoselectivity (up to 98%). In several cases ‘seeding’ with the anti isomer, used to induce the deposition of solid products, improved the conversion (up to 1.8 times) and the anti–syn ratio (up to 98 : 2). The applicability of spontaneous direct aldol reactions in the presence of water was also extended to N-alkyl nortropanones or norgranatanones using an aqueous–organic medium. However, under these conditions only the exo,syn isomers of the N-substituted aldols were obtained. The syn-selectivity for the tropane- and granatane-related aldols is specific for water-promoted reactions and results from thermodynamic control.
anti/syn-diastereomeric ratio (dr) for the solvent-less reaction of tropinone with several aromatic aldehydes. The CPCM-B3LYP/6-31g(d) method reproduces the anti/syn-diastereomeric ratio of the aqueous aldolreaction of tropinone with several aromatic aldehydes with reasonable deviation (0–88%), excellent (0–10)% agreement was found for the reactions of tropinone and granatanone with benzaldehyde. Qualitatively
(68–92%) without racemization by the direct alkylation of amines with benzhydryl chloride under solvent-free conditions. Using the solvent-free conditions (R)-N-benzhydryl-1-phenylethylamine was obtained with the highest yield (92%), purified on ion-exchange resin, and converted to its hydrochloride salt. The resulting chiral amine hydrochloride was transformed into lithium amide/lithium chloride mixture used
can be enantioselectively lithiated by chiral lithium amides and the resulting non-racemic enolate can be reacted with aldehydes giving aldols with enantiomeric excess up to 93% (99% ee after recrystallization). The absolute and relative configuration of the aldol products was determined by NMR spectroscopy and X-ray analysis. Granatanone; aldolreaction; asymmetric synthesis; enantioselective deprotonation;
diastereomers (exo,anti to endo,syn and exo,syn to endo,anti). The exo forms invert to endo isomers in the presence of silica gel. The relative configuration of a new isomer of tropinone aldol accessible synthetically through the direct solventless reaction of tropinone and benzaldehyde in the presence of water was determined as exo,syn by comparison of NMR data of the aldol isomers, in particular vicinal coupling