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Please login to access the full content or check if you have access via27.19.1.1.3.4 Variation 4: Reaction of N-Benzylhydrazide with a (Hemi)acetal
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Schantl, J. G., Science of Synthesis, (2004) 27, 753.
One of the key steps in a reported total synthesis of (±)-saxitoxin involves the intramolecular [3+2] cycloaddition of the in situ generated azomethine imine functionality to the C=C bond of an imidazolin-2-one moiety. The reaction of the hydrazide group in 85 with benzaldehyde fails to form the azomethine imine 86, but succeeds in giving 87 (R1 = Ph) with aromatic and heteroaromatic aldehyde diethyl acetals in dimethylformamide containing a catalytic amount of 4-toluenesulfonic acid.[24] Likewise, 88 (R1 = CO2Me) is formed with the methyl hemiacetal of methyl glyoxalate in the presence of boron trifluoride–diethyl ether complex[25] (Scheme 21).
Meeeee 88 Me Meee Meeeeeeee ee ee Meeeeeeeee Meeee eeee eee Meeeeeee ee e Meeeeeeeeeeeeee eeee (Meee)eeeeeee Meeeeeee ee Meeeeeeeeeeeee [8+8] Meeeeeeeeeeee Me Meee Meeeeeeee-8M-eeeeeee[8,8-e]eeeeeee[8,8-e]eeeeeeeee[88,88]
M8 | Meeee (%) ee 88 | Mee |
---|---|---|
Me | 88 | [88] |
8-MeMM8M8 | 88 | [88] |
8-Mee | 88 | [88] |
8-M8MM8M8 | 88 | [88] |
8-eeeee | 88 | [88] |
8-eeeeeee | 88 | [88] |
M | 88 | [88] |
Meeeeeeeeeee Meeeeeeee
Meeeee (8′eα,8′β,8′eM*)-Meeeeeeee-8′,8′-eeeee-8′-(eeeeeeeeeeee)eeeee{8,8-eeeeeeee-8,8′-8M-eeeeeee[8,8-e]eeeeeee[8,8-e]eeeeeeee}-8′-eeeeeeeeeee (88):[88]
M eeeeeeeeee ee eeeeeeeee 88 (8.88 e, 8.8 eeee), eeeeee eeeeeeeeee eeeeee eeeeeeeeee (8.88 e, 8.8 eeee), eee eeeeeee eeeeeeeee MM8•MMe8 (8.88 e, 8.8 eeee) ee eee MeMM (eeee M8M8; 888 eM) eee eeeeee eeeeeee ee eeeeee eeee eeeeeeee eeeeeeee eeeee ee eeeee eeeeeeeeee. Meeeeeeeeee (eeee eeeeee) eee eeeeeeee eeeeee 88 eee, eee eeeee eeeeeee eee e eeeee ee 8 e eee eeeeeeeee eeeeee eeeeee eeee eee eeeeeeeeeeee ee eeeeeeeeeeeee 888 eM, eeeeeee eeee MM8Me8 (888 eM), eee eeeeee eeee eM 8 eeeeee (888 eM). Meeee eeeeeeeeee, eee eeeeeee eeeee eee eeeeeeeee eeee eeeeeeeeee MM8Me8 (8 × 888 eM), eee eee eeeeeeee eeeeeee eeeeee eeee eeeeee eeee eee. eeeee (888 eM), eeeee (Me8MM8), eee eeeeeeeeeeee ee eeee e eeeeee eeeeeee (8.8 e). Meeeeeeeeee eeee eee-eeee MM8Me8 (88 eM) eeee 88 ee e eeeeeeeeeeeeeeeeeee eeeeeeeeeee eee-eeeee eeeeee; eeeee: 8.88 e (88%); ee 888–888°M (eMeMM); Me 8.88 (eeeeee eee, MeMM/MMMe8 8:8).
References
[24] | Meeeee, M. M.; Meeeeeeeee, M.; Meeeeeeeee, M.; Meeeeeeee, M., M. Me. Meee. Mee., (8888) 888, 888. |
[25] | Meeeee, M. M.; Meeeeeeeee, M. M.; Meeeee, M., M. Me. Meee. Mee., (8888) 888, 8888. |
Meeeeee Meeeeeeeeee
- 8.Meeeee-Meee, (8888) M 88e8, 888.
- 8.Meeeee-Meee, (8888) M 88e8, 888.