Science of Synthesis

Ramón, D. J.; Yus, M., Science of Synthesis: Stereoselective Synthesis, (2011) 2, 369.

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]

‌Meeee 88‌ Meeeeeeeee ee Meeeeeeee Meeee Meeeee Meeeeee Meeeeeeeeeeeee[‌888‌,‌888‌]

Meeee	M	Meeee (%) ee (Me)-‌88‌	Meeee (%) ee (Me)-‌88‌	Mee
8		88e	88e	[‌888‌]
8		88e	88e	[‌888‌]
8		88	88	[‌888‌]

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Mee eeeeee ee eee eeeeee ee eee eeeee eee e eeeee eeeeee ee eee eeeeeeeeeeeeeeeeeeee. Meee, eee eeeeeeee ee eeeeee (M)-eeeeeeee(8-eeeeeeeeeeee)eeeeeeee eeee eeeeeeeeeeee ee eee eeeeeeee ee eeeeeeee(MM) eeeeeeee eeeee (8M,8M)-8-eeeeeee-8-eeeeeeeeeeee-8-ee ee eee eeeee eeeeeeeeeeee (88% ee), eeee eeeeeeeee ee eeeeeeeeeeeee.[‌888‌]

Meeeeeeeeeee Meeeeeeee

(M)-8-[(8M,8M)-8-Meeeeeeee-8-eeeeeeeeeeeeeeee-8M-eeeee-8-eeeee]-8-eeeeeeeeeeeee [(Me)-‌88‌, M = 8-Meeeeeeee-8-eeeeeeeeeeeeeeee-8M-eeeee-8-eeeee]; Meeeeee Meeeeeeee:[‌888‌]

Me e eeee-eeeeeee eeee ee eeeeeeee{[(8M,8M)-8-eeeeeeeee-8-eeeeeeeeeeeeeeee-8M-eeeee-8-eeeee]eeeeee}eeeeeeee (8.888 e, 8.888 eeee) ee eeeee MMM (8 eM) ee −88 °M, e 8.8 M eeee ee MeMe ee eeeeee (8.88 eM, 8.88 eeee) eee eeeee eeeeeeee eeeee ee eeeee eeeeeeeeee. Mee eeeeeeeee eeeeeee eee eeeeeee eee 8 e ee eee eeee eeeeeeeeeee; eeeeeeeeeeee (8.888 eM, 8.888 eeee) eee eeee eeeee. Mee eeeeeeeee eeeeeee eee eeeeeee eee 88 eee eee eeee eeeeeeee ee eee eeeeeeee eeeeeeee ee eee. ee MM8Me (8 eM). Mee eeeeeee eeeee eee eeee eeeeeeeee eee eeeeeeeee eeee Me8M (8 × 88 eM) eee eee eeeeeeee eeeeeee eeeeee eeee eeeee (Me8MM8). Mee eeee eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee, eeeeee 8.888 e ee eeeee eeeeeee, eeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, Me8M/eeeeee/Me8M 8:88:8) ee eeee eee eeeeeee ee e eeeeeee ee eeeeeee; eeeee: 8.888 e (88%).

References