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Please login to access the full content or check if you have access via1.11.11.2 Formation of syn-Stereotriads by Aldol Coupling of Vinyl Ketones and α-Amino Aldehydes
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Schleicher, K. D.; Jamison, T. F., Science of Synthesis: Stereoselective Synthesis, (2011) 1, 561.
In the related reductive aldol coupling of methyl or ethyl vinyl ketone with chiral α-amino aldehydes 62, very good selectivity is observed for the formation of the all-syn-stereotriad 63A (Scheme 36).[45] More rigorously, the major compound obtained is the syn-aldol, anti-Felkin–Anh product. The monoprotection of the α-amino group of the aldehyde is crucial for this selectivity, as hydrogen bonding between the N—H and the aldehyde carbonyl is suggested to play a key role in directing the anti-Felkin–Anh selectivity as well as enhancing aldehyde reactivity through stabilization of the alkoxide in the transition state. By way of comparison, the N-(tert-butoxycarbonyl)-N-methylamino aldehyde affords the syn-aldol, Felkin–Anh product in low yield in the reaction with methyl vinyl ketone.
Meeeee 88 Meeeeeee-Meeeeeee Meeeeeeee Meeee Meeeeeee ee Meeeee eee Meeee Meeee Meeeee ee M-eeee-Meeeeeeeeeeeee-Meeeeeeee e-α-Meeee Meeeeeeee[88]
M8 | M8 | Meeee (%) | ee (88M/88M)e | Mee |
---|---|---|---|---|
Me | Me | 88 | ≥88:8 | [88] |
Me | Me | 88 | 88:8 | [88] |
Me | eMe | 88 | ≥88:8 | [88] |
Me | Me | 88 | ≥88:8 | [88] |
Me | eMe | 88 | 88:8 | [88] |
Me | MM8MMMMMM | 88 | ≥88:8 | [88] |
Me | Me | 88 | ≥88:8 | [88] |
Me | Me | 88 | 88:8 | [88] |
Me | eMe | 88 | ≥88:8 | [88] |
Me | Me | 88 | ≥88:8 | [88] |
Me | eMe | 88 | 88:8 | [88] |
Me | MM8MMMMMM | 88 | ≥88:8 | [88] |
e Meeeeeeeeeeeee eeeee eee eeeeeeeeee ee 8M MMM eeeeeeee ee eee eeeee eeeeeeee eeeeeee.
Meeeeeeeeeee Meeeeeeee
(8M,8M,8M)-8-(eeee-Meeeeeeeeeeeeeeeeee)-8-eeeeeee-8-eeeeee-8-eeeeeeeeeeee-8-eee (88M, M8 = Me; M8 = Me); Meeeeee Meeeeeeee:[88]
Me e 88 ee × 888 ee eeee eeee eeeeeee eeee Me8MM8 (8.8 ee, 8.888 eeee, 88 eee%), eee-8-eeeeeeeeeeeeee (88.8 ee, 8.888 eeee, 88 eee%), Me(eee)8MMe (8.8 ee, 8.888 eeee, 8 eee%), eee M-(eeee-eeeeeeeeeeeeee)-e-eeeeeeeeeeeeee (88 ee, 8.88 eeee) eee eeeee MM8Me8 [888 µM (8.8 M)]. Mee eeee eeee eee eeeeee eee eeeee eee eeeeeee eeeeeee eee eeeeeee eeeeeeee ee M8(e) eee 88 e eeee. Mee eeeeeee eee eeeeee eeeee ee eeeeeeeeee ee M8 eeeee e eeeeeee. Meeeee eeeee eeeeee (88 µM, 8.88 eeee, 8 eeeee) eee eeeee, eee eee eeeeeee eee eeeeeee ee eeee ee 88 °M eee 88 e. Mee eeeeeee eee eeeeeeeeeeee eeee eeeeee eee, eee eee eeeeeee eee eeeeeeee eee eeeee eeeeeeeeeeeeee (eeeeee eee, MeMMe/eeeeee) ee eeeeeee eee eeeee eeeeeeee eeeeeee; eeeee: 88 ee (88%).
References
[45] | Meee, M.-M.; Meeeeee, M. M., M. Me. Meee. Mee., (8888) 888, 88888. |