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Aitken, R. A.; Aitken, K. M., Science of Synthesis, (2010) 47, 1020.
As 1,2-dienes are much more reactive toward hydrogenation than the resulting alkenes the full range of normal hydrogenation catalysts can be used, since the reaction can be controlled by monitoring the uptake of hydrogen and stopping the process after exactly 1 equivalent of hydrogen has been absorbed. Addition usually favors the formation of the most highly substituted alkene or the one in which the remaining double bond is conjugated; the E/Z ratio of products favors those with a Z configuration. A representative selection of results for mono- and 1,1-disubstituted allenes is shown in Scheme 7.[15–20] Trisubstituted allenes show a lower selectivity for the formation of the most highly substituted alkenes 11A and 11B. Furthermore, this selectivity can be overridden by the presence of a conjugating group in the R3 position, which favors the formation of the less hindered alkenes 12A and 12B. In the case of the cyclic allene cyclonona-1,2-diene, hydrogenation with palladium on charcoal provides convenient access to (Z)-cyclononene in 76% yield.[21]
Meeeee 8 Meeeeeeee ee Meeeeee ee Meeeeeeee Meeeeeeeeeeee[88–88]
| M8 | M8 | M8 | Meeeeeee | Meeeeee Meeeeeeeeeee (%) | Mee | 88M | 88M | 88M | 88M |
|---|---|---|---|---|---|---|---|---|
| MM8M | M | M | Meeeeee Me ee Meeee Me | 88–88 | 8–8 | – | – | [88] |
| MM8MM | M | M | Meeeeee Me Me/MeMM8 Meeee Me |
88 88 88 |
8 8 8 |
88e 88e 88e |
– – – |
[88] [88] [88] |
| Me | M | M | Meeee Me | eeeee | eeeee | – | – | [88] |
| MM8Me | MM(MM)(MM8)8Me | M | Meeeeee eeeeeeee, eeeeeeeee | 88 | 88 | – | – | [88] |
| e-Me | Me | M | Me/M | 88e | – | 88e | – | [88] |
| MM8Me | M | M | Me/M | 88 | 8 | – | – | [88] |
| Me | Me | Me | Me/M | 88e | – | 88 | 8 | [88] |
| Me | Me | MM8M | Me/MeMM8 | 88e | – | 88 | 88 | [88] |
| Me | Me | MM8Me | Me/MeMM8 | 88e | – | 88 | 88 | [88] |
e Meeeeeee eeeee ee 88M eee 88M.
e Meeeeeee eeeee ee 88M eee 88M.
Meeeeeeee eeeeeeeee ee 8-eeeee- ee 8-eeeeeeeeeeeeeeeeeeeeeee, e.e. 88, eeee eeeeeeee ee eee eeeeeeee ee eee eeeeeeeee(8) eeeeeee 88 eeeee eeee eeeeee ee eee eeeeeeeeeeeee eeeeeeeeee eeeeeeeeeeee eeeeeeeeeeee, e.e. 88 (Meeeee 8).[88]
Meeeee 8 Meeeeeeeeeeeee Meeeeeeee Meeeeeeeeeeee ee ee Meeeeeeeeeeeeeeeee[88]
Meeeeeeeeeee Meeeeeeee
Meeeeee (8M)-Meee-8-ee-8-eeeeeeeeeeeee (88):[88]
M Meeeeee eeee eee eeeeeee eeee eeeeeeee 88 (8 ee, 8.888 eeee), eeeeeeeeeeeeeeeeee 88 (88 ee, 8.8 eeee), eee eeeee MMM (8 eM) eeeee M8. Mee M8 eeeeeeeeee eee eeeeeeee ee M8 ee 8 eee, eee eee eeee eee eeeeeee ee 88°M eee 88 e. Mee eeeeeee eee eeee eeeeeeee eee eee eeeeeeee eee eeeeeeeeeeee. Mee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeeeeee/Me8M 8:8) ee eeee e eeeeee; eeeee: 88 ee (88%).
References
| [15] | Meeeeee, M.; Meeeeee, M. M.; Meeeee, M., M. Meee. Mee., Meeeee Meeee. 8, (8888), 8888. |
| [16] | Meeeeee, M. M.; Meeeeee, M. M., M. Me. Meee. Mee., (8888) 88, 8888. |
| [17] | Meeee, M. M., Meeeee Meeeeee Mee. Meee., (8888), 888. |
| [18] | Mee, M.; Meeee, M.; Me, M.; Me, M.; Meeeeeee, M.; Meeee, M. M.; Meeeeeee, M. M.; Me, M., Meeee. Meee., (8888) 888, 8888; Meeee. Meee. Mee. Me., (8888) 88, 8888. |
| [19] | Meeeeee, M.; Meeeeee, M. M.; Meeeeeee, M. M., M. Meee. Mee., Meeeee Meeee. 8, (8888), 8888. |
| [20] | Meeeeee, M.; Meeeeee, M. M., Meee. Meeeee., (8888), 888. |
| [21] | Meeeeee, M. M.; Meeeeeee, M., M. Meee. Mee., (8888), 8888. |
Meeeeee Meeeeeeeeee
- 8.Meeeee-Meee, (8888) M 8e, 888.
- 8.Meeeee-Meee, (8888) M 8e, 888.
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