Enolate Generation under Hydrogenation Conditions: Catalytic Aldol Cycloreduction of Keto-Enones
摘要:
[GRAPHIC]Formal heterolytic activation of elemental hydrogen under Rh catalysis enables the reductive generation of enolates from enones under hydrogenation conditions. Enolates generated in this fashion participate in catalytic C-C bond formation via carbonyl addition to aldehyde and, as demonstrated in this account, ketone partners. Notably, the use of appendant dione partners enables diastereoselective formation of cycloaidol products possessing 3-stereogenic centers, including 2-contiguous quaternary centers.
Enolate Generation under Hydrogenation Conditions: Catalytic Aldol Cycloreduction of Keto-Enones
摘要:
[GRAPHIC]Formal heterolytic activation of elemental hydrogen under Rh catalysis enables the reductive generation of enolates from enones under hydrogenation conditions. Enolates generated in this fashion participate in catalytic C-C bond formation via carbonyl addition to aldehyde and, as demonstrated in this account, ketone partners. Notably, the use of appendant dione partners enables diastereoselective formation of cycloaidol products possessing 3-stereogenic centers, including 2-contiguous quaternary centers.
Copper-Catalyzed Tandem Conjugate Addition−Electrophilic Trapping: Ketones, Esters, and Nitriles as Terminal Electrophiles
作者:Kyriacos Agapiou、David F. Cauble、Michael J. Krische
DOI:10.1021/ja030603l
日期:2004.4.1
Exposure of enone substrates 1a-18a, which possess appendant ketone, ester, and nitrile moieties, to Et2Zn in the presence of catalytic Cu(OTf)2/P(OEt)3 provides the cyclized products in good to excellent yields and diastereoselectivities. These results represent the first use of ketones, esters, and nitriles as terminal electrophiles in Cu-catalyzed conjugate addition-electrophilic trapping.
Access to Polyfunctionalized Diquinanes, Hydrindanes, and Decalines via TiCl<sub>4</sub> Promoted Michael–Aldol and Baylis–Hillman Reactions
The addition of 0.5 equiv of TiCl4 to (cyclo)alkanones tethered to alpha,beta-unsaturated ketones afforded polyfunctionalized diquinanes, hydrindanes, and decalines. These products, resulting from a Michael-aldol or a Baylis-Hillman reaction, can be obtained with high or total diastereoselectivity in moderate to high yields. These scaffolds represent interesting building blocks for the synthesis of complex natural products.