- Domino Michael-aldol annulations for the stereocontrolled synthesis of bicyclo[3.3.1]nonane and bicyclo[3.2.1]octane derivatives
-
Domino Michael-aldol annulation of cycloalkane-1,3-diones with enals affords a general route to 6-hydroxybicyclo[3.3.1]nonane-2,9-diones and 2-hydroxybicyclo[3.2.1]octane-6,8-diones, notably in one-pot procedures under convenient conditions. The annulation is shown to be compatible with one or more substituents at six positions of the bicyclo[3.3.1]nonane-2,9-dione scaffold. In some cases, the relative configuration of the product can be controlled by the appropriate choice of solvent, base and temperature for the annulation. In contrast to the chair-chair conformations usually adopted, the bicyclo compounds derived from 2,4,4-trimethylcyclohexane-1,3-dione possessed boat-chair conformations. Oxidation of the annulation products gave the corresponding bicyclo triketones.
- Promontorio, Rossella,Richard, Jean-Alexandre,Marson, Charles?M.
-
p. 114412 - 114424
(2016/12/24)
-
- A brief and stereoselective synthesis of limonoid models, with antifeedant activity against Locusts migratoria
-
A short stereoselective preparation of havanensin-type limonoid models is reported. The synthesis is based on a radical domino reaction of an epoxyketone to a bicyclic hydroxyketone, and is achieved in six and nine steps from simple cyclohexenones. The epoxyhavanensin derivatives show significant antifeedant activity against Spodoptera littoralis and Spodoptera frugiperda, and the epoxyketone 21 shows potent antifeedant activity against Locusts migratoria.
- Fernández-Mateos,Ramos Silvo,Rubio González,Simmonds
-
p. 7809 - 7816
(2007/10/03)
-
- Revisiting [3 + 3] route to 1,3-cyclohexanedione frameworks: Hidden aspect of thermodynamically controlled enolates
-
We have revisited the traditional consecutive Michael-Claisen [3 + 3] process (MC-[3+3]) promising the synthesis of a cyclohexane-1,3-dione derivatives from nonactivated simple ketones and enoates and evaluated its potential in modern organic synthesis. Twenty to thirty examples were demonstrated to be effective. The reactions exhibited remarkable regioselectivity with the Michael addition proceeding through nucleophilic attack by the more hindered site of the ketones without exception. The subsequent Claisen condensation resulted in the formation of carbon-carbon bonds between less hindered site of the ketones and acyl carbon of the enoates. The MC-[3+3] process described is useful for the synthesis of Taxol A-ring synthons in multigram quantities and for the synthesis of other six-membered carbocyclic compounds. A number of control experiments have been conducted to provide strong support for the mechanism of this MC-[3+3].
- Ishikawa, Teruhiko,Kadoya, Ryuichiro,Arai, Masaki,Takahashi, Haruka,Kaisi, Yumi,Mizuta, Tomohiro,Yoshikai, Kazusa,Saito, Seiki
-
p. 8000 - 8009
(2007/10/03)
-