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DOI: 10.1055/sos-SD-202-00157

Ramón, D. J.; Yus, M.Science of Synthesis: Stereoselective Synthesis, (20112369.

The diastereoselectivity observed for this approach has in general been very low when the distance between the stereogenic center and the metallic atom is further than one bond, for instance α-functionalized organometallics.[‌143‌] Only in the case when both chiral nucleophiles and electrophiles are used is the obtained diastereoselectivity very high for the corresponding matched pair.[‌144‌,‌145‌] This result notwithstanding, some α-functionalized organometallics are able to perform the nucleophilic addition with a reasonable level of diastereoselectivity. The reaction of primary organolithium reagents (obtained by transmetalation using butyllithium and the stannyl derivative 35) with benzaldehyde gives a mixture of both diastereomers 36 (Table 18). In the case of imidazolidinone derivatives, the bulk of the substituent at the nitrogen atom seems to have some impact on the diastereoselectivity, with the most hindered phenyl derivative giving the best result (entry 2).[‌146‌] The diastereoselectivity is even higher in the case of the related ketal derivative (entry 3).[‌147‌]

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