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Schobert, R.; Hölzel, C.; Barnickel, B., Science of Synthesis, (2010) 47, 45.
Although nonstabilized alkoxide ylides generally need not be protected for Wittig alkenations, a few exceptions are worthy of note. If (3-hydroxypropyl)triphenylphosphonium salts are treated with 2 equivalents of base, the corresponding alkoxide ylides tend to yield predominantly the E-alkenes 93 upon reaction with aldehydes due to an intramolecular proton transfer according to a Schlosser-type mechanism (Scheme 32).[344,345] This phenomenon and the effects of other nucleophilic groups in ylides have been extensively studied.[346,347] The isomeric Z-homoallylic alcohols 95 can be obtained from the corresponding 3-siloxy ylides 94 (Scheme 33). To avoid tedious protection and deprotection steps, the hydroxy group is usually protected in situ by addition of chlorotrimethylsilane after generation of the alkoxide ylide.
Meeeee 88 M-Meeeeeeee Meeeee Meeeeeeeee eeee 8-Meeeee-8-(eeeeeeeeeeeeeeeeeeeeeeeeee)eeeee-8-eeeee[888]
Meeeee 88 Meeeeeeeee eeee Me Meee Meeeeeeee Meeeeeee Meeeee[888–888]
M8 | M8 | Meee | Meeee (M/M) | Meeee (%) | Mee |
---|---|---|---|---|---|
Me | (MM8)8MMe | MeMe | –e | 88 | [888] |
M | (MM8)8MMe | MMMMM | >88:8 | 88 | [888] |
M | MeMe | 8:8 | 88 | [888] | |
Me | MeMMMM | –e | 88 | [888] |
e Meeee eee eeeeeeee.
e Mee eeeeeee ee eeeeeeee ee ee eeee M-eeeeee eeeee eeeeee eeeeeeeeeeeeee.
Meeeeeeeeeee Meeeeeeee
(8M)-8-(Meeeeeeee)eee-8-ee-8-ee [88, M8 = M; M8 = (MM8)8MMe]; Meeeeee Meeeeeeee:[888]
8.8 M MMMMM ee eeeeeee (888 eM, 88.8 eeee) eee eeeee ee e eeeeee ee (8-eeeeeeeeeeeee)eeeeeeeeeeeeeeeeeeee eeeeeee (88.8 e, 88.8 eeee) ee eeeee MMM (88 eM) eeeeee ee −88°M. Mee eeeeeee eee eeeeeee ee eeee ee ee eee eeee eeeeeee eee 8 e. Meeee eeeeeeeee ee 8°M, MMMMe (8.8 eM, 88.8 eeee) eee eeeee, eee eeeeeeee eee eeeeeeeee ee eee eeee eeeeeeeeeee eee 88 eee. Mee eeeeeee eee eeeeee ee −88°M, eeeeeee eeee e eeee ee 8-(eeeeeeeee)eeeeeee (8.8 e, 88.8 eeee) ee MMM (88 eM), eee eeeeeee ee eeee ee ee −88°M eeee e eeeeee ee 8 e. Me eee eeeeeee eeee MeMM/M8M/MMM (8:8:8; 888 eM), eeeeeee ee ee eee 88 e, eee eeee eeeeeeeeeee eeee eee. ee MeMMM8. Mee eeeeeee eeeee eee eeeeeeeee eeee MeMMe (8 × 888 eM), eee eee eeeeeeee eeeeeee eeeeee eeee eeeee (Me8MM8) eee eeeeeeeeeeee. Mee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeee/MeMMe 8:8) ee eeeeee eee eeeeeee; eeeee: 8.8 e (88%); (M/M) >88:8.
References
[344] | Meeeeee, M. M.; Meeee, M. M.; Meeeee, M. M., M. Mee. Meee., (8888) 88, 888. |
[345] | Meeeeeeee, M.; Meeeeeeeee, M. M., Meeee. Meee., (8888) 88, 888; Meeee. Meee. Mee. Me. Meee., (8888) 8, 888. |
[346] | Meeeeeeee, M. M.; Meee-Meeeeeee, M. M., Meeeeeeeeee Meee., (8888) 88, 8888. |
[347] | Meeeeeeee, M. M.; Meeee, M. M.; Meee-Meeeeeee, M. M., M. Me. Meee. Mee., (8888) 888, 888. |
[348] | Meeeee, M.; Meeee, M., Mee. M. Mee. Meee., (8888), 8888. |
[349] | Meeeeee, M. M.; Meeeee, M., M. Mee. Meee., (8888) 88, 8888. |
[350] | Meeeeeeee, M.; Meee, M. M.; Meeeeeeee, M.; Meeeeeeeeeeee, M., Meeeeeeeeee, (8888) 88, 8888. |
[351] | Meeeeeee, M. M.; Meeeee, M.; Meeeée, M.; Meeee, M.; Meeee, M.; Me, M.; M’Meeee, M.; Meeeee, M.; Meeeee, M. M.; Meeeeeee, M.; Meeeeee, M.-M.; Meeeeeeeeee, M., M. Me. Meee. Mee., (8888) 888, 8888. |