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DOI: 10.1055/sos-SD-210-00013

Chebanov, V. A.; Gorobets, N. Yu.; Sedash, Yu. V.Science of Synthesis: Multicomponent Reactions, (2014156.

Catalytic asymmetric multicomponent reactions present the most straightforward approach to enantiomerically pure 3,4-dihydropyrimidin-2(1H)-one derivatives. The first article concerning application of cerium(III) chloride [or indium(III) chloride] with chiral ligand 31 in the Biginelli reaction involving benzaldehyde, urea, and methyl acetoacetate was published by Muñoz-Muñiz and Juaristi (Scheme 17).[‌201‌] However, this method results in either high general yields (93%) with low enantiomeric excess (24%) or values of enantiomeric excess up to 40% with mediocre yield (~25%). A significantly more efficient asymmetric Biginelli reaction involves application of 10 mol% of ytterbium(III) trifluoromethanesulfonate and chiral ligand 32 to catalyze the multicomponent reaction between aromatic aldehydes, urea, and ethyl or isopropyl acetoacetate to give 2-(thi)oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates 33 in high yields with excellent enantioselectivity (80–99% ee).[‌200‌] The influence of the reaction conditions, type of salt, and character of the Ar1 substituent on the general outcome and enantiomeric excess was also analyzed.

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