Chemistry of higher order, mixed organocuprates. reactions of α,β-unsaturated ketones.
作者:Bruce H. Lipshutz、Robert S. Wilhelm、Joseph Kozlowski
DOI:10.1016/s0040-4039(00)87698-4
日期:1982.1
Organocuprates of general formula R2Cu(CN)Li2 react rapidly with α,β-unsaturated ketones at low temperatures and in high yields to deliver ligands in a conjugate manner. These reagents apparently do not require the use of additives for stabilizing or solubilizing purposes.
[3 + 3] Annulation Based on 6-Endo-Trig Radical Cyclization: Regioselectivity and Diastereoselectivity
作者:Dale E. Ward、Yuanzhu Gai、Brian F. Kaller
DOI:10.1021/jo00129a024
日期:1995.12
The development of a [3 + 3] annulation strategy based on sequential ''two-electron'' and ''one-electron'' allylation of beta-substituted aldehydes and derivatives with the bifunctional isobutene conjunctive reagent 1 is described. The key step involves an unusual 6-endo-trig radical cyclization. Yields of 6-endo products are improved if the PhS group is oxidized to a PhSO(2) group prior to cyclization. The structural factors affecting the regioselectivity and stereoselectivity of the cyclization are examined. In general, the stereoselectivity of 6-endo-trig cyclization of 5-hexenyl radicals can be rationalized by conformational analysis of chairlike transition states and can be calculated effectively with an MM2 force field model, High 6-endo regioselectivity requires a strong driving force. Fragmentable allylic groups (R(3)Sn, PhSO(2), and to a lesser extent PhS) are shown to be sufficiently activating to achieve 6-endo regioselectivity.
Kinetic Resolution of Chiral Cyclohex-2-enones by Rhodium(I)/binap-Catalyzed 1,2- and 1,4-Additions
作者:Andreas Kolb、Sebastian Hirner、Klaus Harms、Paultheo von Zezschwitz
DOI:10.1021/ol300387f
日期:2012.4.20
The feasibility of kinetic resolutions of racemic monosubstituted cyclohex-2-enones by Rh/binap-catalyzed reactions was investigated. 1,2-Addition of AlMe3 to the 5-substituted derivatives furnished allylic alcohols in the matched case, while the less reactive enantiomers were either left over or transformed into trans-3,5-disubstituted cyclohexanones in parallel or sequential 1,4-additions. Altogether, these represent regiodivergent reactions on racemic mixtures. In contrast, 1,4-addition of aryl groups led to inferior results since either catalyst or substrate control dominated.