The direct and enantioselective γ‐alkylation of α‐substituted α,β‐unsaturated aldehydes proceeding under dienamine catalysis is described. We have found that the Seebach modification of the diphenyl‐prolinol silyl ether catalyst in combination with saccharin as an acidic additive promotes an SN1 alkylation pathway, while ensuring complete γ‐site selectivity and a high stereocontrol. Theoretical and
描述了在二烯胺催化下进行的α-取代的α,β-不饱和醛的直接和对映选择性的γ-烷基化。我们发现,二苯丙脯氨醇甲硅烷基醚催化剂的Seebach改性与糖精作为酸性添加剂的组合可促进S N 1烷基化途径,同时确保完全的γ。现场选择性高立体声控制。理论和光谱研究为由2-甲基戊-2-烯醛与手性胺缩合衍生的共价二烯胺中间体的构象行为提供了见解。讨论了立体诱导机制的含义。
A new umpolung for direct γ-regioselective nucleophilic addition of alcohols to γ-enolizable α,β-unsaturated aldehydes
作者:Satoru Arimitsu、Mari Oshiro、Tsunaki Yonamine
DOI:10.1016/j.tetlet.2017.05.058
日期:2017.6
A direct γ-regioselective nucleophilic addition of alcohols toward γ-enolizable α,β-unsaturatedaldehydes was developed using a catalytic amount of MeSO3H (30 mol%) and a stoichiometric amount of chloranil (1.0 equiv) as the oxidant. The addition of hexafluoroisopropanol (HFIP) was found to accelerate this cross-dehydrogenative coupling, furnishing diverse alcoholic adducts with high γ-regio- and
Tandem-Directed Regioselective Hydroformylation/β-Elimination: A Practical Method for the Synthesis of Enals
作者:Bernhard Breit、Achim Bruch、Antje Gebert
DOI:10.1055/s-2008-1067140
日期:2008.7
A practical synthesis of α,β-unsaturated aldehydes by a tandem-directed hydroformylation/β -elimination process of allylic o-DPPB esters is reported. The o-DPPB group served as an effective controller for regioselectivity of the hydroformylation towards the desired aldolate isomer, and was subsequently eliminated in situ by mild standard bases. The reaction is rather general for the preparation of
Combining Palladium and Chiral Organocatalysis for the Enantioselective Deconjugative Allylation of Enals via Dienamine Intermediates
作者:Guang Hu、Stacey E. Brenner-Moyer
DOI:10.1021/acs.joc.1c02591
日期:2022.1.7
underwent this transformation in high yield and ee, and products can be readily transformed into γ-allyl enals via a Cope rearrangement without erosion of ee. This transformation was used to install the quaternary stereocenter in (S)-bakuchiol, enabling completion of a concise formal synthesis.
报道了 enals 的催化对映选择性去共轭烯丙基化。多种烯醛在高产率和ee上经历了这种转变,并且产物可以通过Cope重排容易地转化为γ-烯丙基烯醛,而不会侵蚀ee。该转换用于在 ( S )-补骨脂酚中安装四元立体中心,从而能够完成简明的正式合成。
Improvement of primary-amine-catalyzed asymmetric α-benzoyloxylation of α-branched enals by a synergistic effect of water and sulfonic acids
作者:Satoru Arimitsu、Emi Gima
DOI:10.1016/j.tetlet.2020.152032
日期:2020.6
The asymmetric α-benzoyloxylation of α-branchedenals developed by List was reinvestigated to further improve its reaction efficiency and enantioselectivity. After optimizing the reaction conditions, the synergistic effect of water and sulfonic acid in DMSO was revealed. The reaction efficiency was improved reducing the reaction time, and moderate enantioselectivities (up to 81% ee) with excellent
重新研究了List所开发的α-支链烯键的不对称α-苯甲酰氧基化反应,以进一步提高其反应效率和对映选择性。优化反应条件后,揭示了水和磺酸在DMSO中的协同作用。缩短了反应时间,提高了反应效率,并实现了中等的对映选择性(最高81%ee)和极佳的E选择性(E / Z => 20/1)。尽管区域选择性不高(α/γ= 1 / 1–6 / 1),但α-区域异构体2a已成功用于合成由含氧季铵碳和两个烯丙基单元组成的高立体控制化合物(E / Z = 20 / 1,20/1)。