reagents as iBu3A1, PhC=CA1Et2, and Et2A1SPh mediate the title reactions in three different directions. (1) [3,3]sigmatropic rearrangement producing 7-membered rings. (2) isomerization to form vinylcyclopropane derivatives and (3) SN2 type reaction with phenylthio anion via oxolane ring opening.
诸如i Bu 3 A1,PhC = CA1Et 2和Et 2 A1SPh的有机铝试剂可在三个不同方向上介导标题反应。(1)产生7元环的[3,3]σ重排。(2)异构化形成乙烯基环丙烷衍生物,和(3)经由氧戊环开环与苯硫基阴离子进行S N 2型反应。
Regioselective and Stereospecific Rhodium-Catalyzed Allylic Cyanomethylation with an Acetonitrile Equivalent: Construction of Acyclic β-Quaternary Stereogenic Nitriles
作者:Mai-Jan Tom、P. Andrew Evans
DOI:10.1021/jacs.0c02316
日期:2020.7.15
A highlyregioselective and stereospecific rhodium-catalyzed cyanomethylation of tertiary allyliccarbonates for the construction of acyclic β-quaternary stereogenic nitriles is described. This protocol represents the first example of a metal-catalyzed allylicsubstitution reaction using a triorganosilyl-stabilized acetonitrile anion, which permits access to several carbonyl derivatives that are challenging
π-Allylic palladium complexes reacted with conjugateddienes to give diene-inserted products. Isoprene gave l,l-disubstituted allyl complexes rather than 1,2-disubstituted ones. Two types of allylic complexes were studied, and halogen-bridged dimer complexes showed lower reactivity than acetylacetonato complexes. When the allylic group or diene was varied, the reactivity decreased in the order: allyl
complexes as a catalyst in dehydrative reactions with allylic alcohols. There is often an improvement in yield and, in particular, indium(III) chloride outperforms gold(I) as a catalyst in chemoselective reactions. For example, substrates with pendent alkyne or alkene groups react poorly under gold(I) catalysis, but are better tolerated under indium(III) chloride catalysis.
Rhodium-Catalyzed Allylic Substitution with an Acyl Anion Equivalent: Stereospecific Construction of Acyclic Quaternary Carbon Stereogenic Centers
作者:P. Andrew Evans、Samuel Oliver、Jungha Chae
DOI:10.1021/ja306602g
日期:2012.11.28
A highly regio- and stereospecific rhodium-catalyzed allylic alkylation of tertiary allylic alcohol derivatives with a cyanohydrin pronucleophile is described. This direct and operationally simple protocol provides a fundamentally novel approach toward the synthesis of α-quaternary substituted ketones and circumvents many of the inherent problems associated with conventional enolate alkylation reactions