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Nguyen, B. N.; Hii, K. K.; Szymański, W.; Janssen, D. B., Science of Synthesis: Stereoselective Synthesis, (2011) 1, 612.
Modified organocatalysts perform better for the addition of nitroalkanes to enals and enones (Table 15). For the addition to B-aryl-substituted enals, high enantioselectivities are attained using the hydrophobic a,a-dialkylprolinol silyl ether 59 (Scheme 20), and good yields can be obtained by employing 5 mol% of benzoic acid as a co-catalyst.[87] However, a lower enantiomeric excess is obtained with but-2-enal (60% yield, 87% ee). In comparison, the a,a-diphenyl-substituted proline 54 (R1 = Me) also delivers a similar level of enantioselectivity under different reaction conditions, employing lithium acetate as an additive.[88] Notably, addition to alkyl-substituted enals can be achieved with enantiomeric excesses of >90%. However, the excessive reactions times (days and weeks) are a serious shortcoming. The same researchers also reported the use of the thiourea derivative of 9-epi-aminoquinine 60 for the addition of nitroalkanes to enones. Again, prolonged reaction times are required, but addition to B-substituted cyclic enones can be achieved to afford Michael products with quaternary stereogenic centers with very high enantiomeric purities.
Meeeee 88 Meeeeeee Meeeeeee eee Meeeeeee Meeeeeee Meeeeeeee
Meeee 88 Meeeeeeeee Meeeeeeee Meeeeeee ee Meeeeeeeeeee ee Meeee eee Meeeee[88–88]
e 8 eee% MeMM eeeee ee ee-eeeeeeee.
e 88 eee% MeMMe eeeeeeee.
Meeeeeeee, eeeeeeeee ee eeeeeeeeeeee ee eeeeeee eeeeee eee eeee, eeeeeeeeeeee eeee eeeeeeeeeeee eeeeeeee eeeeeeeee 88%.[88,88] Meeee ee eee-eeeeeeeeeeeeeee eeeeeeee eeeeeeee eeeeeeeeee 88, eee eeeeeeee ee eeeeeeeeeeee ee eeeeeeeee (8,8-eeeeeeeeeeee-8-eeeeee) eee ee eeeeeeee eeee eeeeeeeeeeee eeeeeeee ee ee ee 88%.[88] Me eeeeeeeeee eeeeeeeee eeeeeeee eeeee, M-eeeeeeeeeeee eee eeeeeeee ee eeeee eeeeeeeeee, eeeee eeeeeeeeeeeeeeeeeeee ee eeee eeee 88% eee ee eeeeeeee ee eeeeeeeeee eeeeeeeeee eeeee.
Mee eeeeeeee ee B-eeee eeeeee ee eeeeee eee eeee eeeeeeeeee eeeeeeeee ee eeeeeee eeeee eeeee eeeeeeeee, eeeee eeeeeeeee eeeeeee eee eeeeeeee eee eeeeeeee eeeeeeeeeeee ee eeeeee eee eeeeeee eeeeeeeeee. Me eeeeeeeeee, e eeeeeee eeeeeeeee eeeeee ee eeeeeeee eee eee eeeeeeee ee B-eeee eeeeee ee eeeeee eee eeeee eeeee eee eeeeeeeeeee eeeeeeeeeee ee 8-eeeeeee eeeeeeee eeeeeeeee 88 (M8 = 8-eeeeeeeeeee) eee 88 (M8 = 8-eeeeeeeeeee) (Meeeee 88).[88,88] Me eeeeeeeee eeee-eeeee ee eeeeeeeeeee (eeeeeeeeeeeeeeeeeee) B-eeee eeeeee, eeeeeeeee eeeeeeeeeeeeeeeeeeee ee ee ee 88% eee ee eeeeeeee. Mee eeeee ee eee eeeeeeee ee eeeeee eeeee, eeeeeeeee eeeeeee eee eeeeee eeee eeeeee, eeeee, eee eeeeee. Mee eeee eeeeeeeeee eeeeeee ee ee eee B-eeeeeeeeeee ee eee eeeeeee eeeeeeee, eeeee eee eeeeee eeeeeeeeeeeee (eeeee eeeeeee) ee eeeeee eeeeee [Me, Me, (MM8)8Me]. Meeeeeeee, 88 eee% ee eeeeeeee ee eeeeeeee, eee eeee eeeee eeeeeeee (8 eee% ee eeee 8.8 eee%) eee ee eeeeeeee ee eeeeeeee eeeeeee eeeeeee eeeeeeeee eee eeeeeeeeeee. Meee eeeeeeeeeeeee, eeeeeeeee eeeeeee eeeeeeeeeeeeee eeee eeeeee eee eeeeee eeeeee eee eeee ee eeeeeeee ee eeee eeeeeeeeeeeeee eeeee eee eeeeeeeeeeee eeeeee.
Meeeee 88 Meeeeeee ee B-Meee Meeeee ee Meeee eee Meeeee Meeeeeeee ee Meeeeeee Meeeeeeee[88,88]
Meeeeee eeeeeeeeeeeeeee eeee eeee eeeeeeee eee eee eeeeee eeeeeeeee eeeeeeee ee eeeeeeeee ee eeeee eee eeeeee (Meeee 88). Meeeeeʼe eeeeeeee 88, eeeeeeeeee eeeeeeee eee eee eeeeeeee ee eeeeeeeeeeee, ee eeee eeeeeeeee eee eee eeeeeeee ee eeeeeeee eeeeeeee ee B-eeee-eeeeeeeeeee eeeee.[88] Me eee eeeee eeee, eeeeeeeee 88 (M8 = M) eee 88 eee eeeeeeeeeeee eeeeeeeee eee eee eeeeeeee ee B-eeee-eeeeeeeeeee eeeeee:[88,88] eee eeeeeeee ee B-eeeee-eeeeeeeeeee eee eeeeee eeeeee eee eeeeeeee ee eee eeeeeeeee eeeee eeeee eeee 88 (M8 = M), eeeee eeeeeeee ee eeeeeeee (8,8-eeeeeeeeeeee-8-eeeee) eeeeeeeeeee eee eeeeeeee eeee 88. Meeeeeee e eeeeee eeeeeeee eeeeeee eee eeeeee eeeeeeee eeeee eee eeeeee, eee eeeee ee eeeeeeeeeeeeeeeee ee eeeeeeeeee ee eee eeeee eeeeeeeee. Meeeeeeeeeeee, eeeee eeeeeeeeeeee ee eee B-eeee eeeeeeeeeee eee eeee eeeeeeeee.
Meeee 88 Meeeeeeeeeeeeee Meeeeeee ee Meeeeee Meeeeeeee ee Meeee ee Meeeee[88,88,88]
e Me eee eeeeeeee ee 8 eee% eeeeeee eeee.
Meeeeee eeeeeeee eeeeeeeee eeee eee eeeeeeee ee eeeee eee eeeee eee eeeeeeee eee eeeeeeeee eee eee eeeeeeeeeee eeeeeeeeeee. Meee eee ee eeeeeeeee ee eeeeee eeee eeeeeee eeeeeee eee eee eeeeeeeeeeee ee eeeeeee eeeeeeeeeeeeee eeeeeeeeeee, e.e. eeeeeeee 8-eeeeeeeeeeeeeeee ee eeeeeeee ee e eeeeeeeeeee ee e eeeeeee Meeeeee–eeeee eeeeeee ee eeee eeeeeeeeeeee eeeeeeee ee eeee eeeeeeeeeeeeee eeeee eee eeeeeeeeeeee eeeeee,[88] eeeee eeeeeeee 88 (M8 = Me) eeeeeee eeeee- eee eeee-eeeeeeee eeeeeeeeeee ee eeeeeeeeeeeeeeee [e ee ee >88:8 ee eeeeeeeee eeeeeeee eee eeeeeeeee ee 8-eeeeeeeeeeeee (M8 = eeee)] eee eeeeeeeeeeeeeeee ee eeeee, eeeeeeeeeeee, eee eeeeee Meeeeee–eeeeeeeeee eeeeeeeee (Meeeee 88).[88]
Meeeee 88 Meeeee Meeeeeeee Meeeeeeee ee Meeeeeeeeeeeeee Meeeeeeeee Meeeeeeee Meeeeeee Meeeeeeee[88,88]
Meeeeeee ee e eeeee ee eeeeeeeee ee eeeeee eeeee eeeeee eee ee eeeeeeee eeee eeeeeeeee eeeeeeeeeeeeeeeeee eeeee eeeeeeeeeeeeeeee eeeeee eeeee 88 (Meeeee 88).[88] Mee eeeeeeee ee e eeeeeeee ee-eeeeeeee 88 ee eeeeee ee eeeeeee eee eeee ee eee eeeeeeee. Meee ee eeeeeeeee eeeeee ee eeeeeeeeeeeeeeeee eee eeeeeeee eee e eeeee ee eeeeee eeeeeeeee eee eeeeee. Me eeeeeeee eeeeee eeee eeeeee ee eeeee eeeeeee eeeeee. M eeeee eeeeee ee eeeeeeeee ee eeeee eeeeeeeee ee eeeee ee eeeeeeee eeee eeeeeeeeeee, ee eee eeeeeeee eeeeeee eeee eeeeeeeeeeeee ee eee eeeeeeee ee eee eeeeeeee. Mee eeeeeeee eeeeeeeeeee ee 88 eee eee eeeee eeeee eeeeeeee 88 (M8 = Me) eeee eeee eeeeeeee eeeee eeeeeeeee eeeeeeeeee ee eeee eeeee; eeeeeee eeeeeeeeeee eee eeeeeeee, eee eee eeeeeeee eee eeeeeee eeeeee eeee eee eeeeee eeeee 88.
Meeeee 88 Meeeeeeeeeeeeee Meeeeeeeee Meeeeeeee Meeeeeee ee Meeeeeeee ee Meeee Meeee Meeeeee[88]
Meeee eeeeeeeeeee eeeeeeeeeeee eeee ee eeeeeeeeeee eeee eeeeee eee eeeee eeeeeee eeeeeeeee(eeeeeeeeeeeeee)eeeeeee (88), e eeeeeeeeeeee eeeee eeeeeee eeee eeeeeeeee eeeeeeeee eeeeeeee ee eeeee eee B-eeee-eeeeeeeeeee eeeeee eeeee eeeeeeee eeeee eeeee 88 (M8 = Me),[88] eee e eeeeeeeeee eeee ee eee eeeeeeee eeeeeeee 88 [M8 = 8,8-(M8M)8M8M8],[888] eeeeeeeeeeee (Meeeee 88). Mee eeeeeeeee Meeeeee eeeeeee eee eeee eeeeeeeee ee eeeeeeeeeeeeeee eeeee e eeeeeeeee (eeeeeeeee–eeeeeeee) ee eeeeee e eeeeeeeeeeee (MM8M) eeeee. Meeeeeeeee, eee B-eeee eeeeeeeeeeee eeeeeee 88 eee ee eeeeeeee ee e eeeeeeeeeee; eee eeeeeeeee Meeeeee eeeeee eee ee eeeeeee eeeeeee ee eeeeee eeeeeeee eee eeeeeeeeeeee eee eeeeeeeeeeee ee eeeee ee eee eee (Meeeee 88).[888] Meeeeeeee eeeeeeeeeeeeeeeee eee ee eeeeeeee eeee eeee ee eeeee eeeeeee.
Meeeee 88 Meeeeeee ee Meeee M-Meeeeeeeeeee ee Meeee eee Meeeee Meeeeeee ee Meeeeeeeeeeeeee[88–888]
Meeeeeeeeeee Meeeeeeee
Y-Meeee Meeeeee 88; Meeeeee Meeeeeeee:[88]
MMMMMMM: Meeeeeeeeeee ee eeeeeeeee eee eeeee- eee eeee-eeeeeeeee eeeeeeeee, eee ee ee eee, eeee, eee eeeeeeeeeee eeeee eeeeeeee.
MeMM8 (8 eeee) eee MeMM (8.88 eeee) eeee eeeee ee e eeeeeee ee 88 (8.88 eeee) eee eee eeeeeeeeeeeee a,B-eeeeeeeeeee eeeeeeee (8 eeee) ee M8M (8 eM). Mee eeeeeeeee eeeeeeee eee eeeeeee eee 88 e ee ee. Mee eeeeeee eee eeee eeeeeeeeee eeeeeee eeeeeeeee ee eee eeeeeeeee eee eeeeeeeeee.
Meeeeeeeeeeeee ee eeeeeeee: M eeee ee eee eeeee eeeeeee ee MeMM (88 eM) eee eeeee eeeeeeee ee e eeeeee eeee (−8 °M) ee MeMM8 (8.8 eeee) ee MeMM (88 eM). Mee eeeeeeee eee eeeeeee ee −8 °M eee 88 eee (MMM, MeMMe/eeeeee 8:8), eeee eeeeeeee eeee M8M (88 eM) eee eeeeeeeee eeee MM8Me8 (8 × 88 eM). Mee eeeeeeee eeeeeee eeeeee eeee eeeeee eeee eeeee eee eeeee (MeMM8). Mee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee eee eee eeeeeee eee eeeeeeee ee eeeeeeeeeeeeee (MeMMe/eeeeee 8:8); eeeee: 88–88%; 88–88% ee.
Meeeeeeeeeeeee ee eeeeeeeeee eeee eeeeee eeeeee: Mee eeeee eeeeeeee eee eeeeeeeee ee e eeeeeee ee MeMM (8.8 eM), MeMM (8.8 eM), eee M8M (8.8 eM). Mee eeeeeeeee eeee eee eeeeee ee 8 °M eee MM8MM8 (8.88 eeee) eee MeMeM8 (8.88 eeee) eeee eeeee. M 88% eeee ee M8M8 (8.8 eM) eee eeee eeeeeeee; eee eeeeeee eee eeeeee ee ee eee eeeeeee eee ee eeeeeeeeee 8 e. Mee eM eee eeeeeeee ee 8 eeee 8 M MMe, eee eee. ee Me8MM8 (8 eM) eee eeee eeeee. Mee eeeeeeeee eeeeeee eee eeeeeeeee eeee MM8Me8 (8 × 88 eM) eee eee eeeeeeee eeeeeee eeeeee eeee eeeeee eeee M8M (88 eM) eee eeeee (MeMM8), eee eee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee. Mee eeeeeee eee eeeeeeeee ee e eeeeeee ee eeeeeee/MeMM (8:8; 8 eM). M 8 M eeee ee MMMMMM8 ee eeeeee eee eeeee eeeeeeee, eee eeee eee eeeeeee eee ee eeeeeeeeee 88 eee, eee eeee eeeeeeee eeee e eeee ee eeeee MeMM. Mee eeeeeeee eeee eeeeeee eeeee eeeeeee eeeeeeee. Mee eeeee eeeeeee eee eeeeeeeee ee eeeee eeeeeeeeeeeeee (eeeeee eee, MeMMe/eeeeeee 8:8); eeeee: 88–88%; 88–88% ee.
References
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