Dual Amine and Palladium Catalysis in Diastereo- and Enantioselective Allene Carbocyclization Reactions
摘要:
A pyrrolidine and Pd catalyzed diastereoselective carbocyclization of aldehyde and ketone-linked allenes has been developed. The cooperative organo/metal-catalyzed cyclization reaction, which presumably proceeds via an enamine intermediate, is efficient and broad in scope. Also, it has been extended to a catalytic asymmetric variant using diarylprolinol-based organocatalysts to afford substituted cyclopentane and pyrrolidine reaction products in up to 82% ee.
P-BEMP: A New Efficient and Commercially Available User-Friendly and Recyclable Heterogeneous Organocatalyst for the Michael Addition of 1,3-Dicarbonyl Compounds
Michaeladdition of 1,3-dicarbonyls with various Michael acceptors has been found to be catalyzed by commercially available, user-friendly and recyclable N-phenyl-tris(dimethylamino)iminophosphorane immobilized on polystyrene resin (P-BEMP). The reaction does not require anhydrous solvents or inert atmosphere and proceeds smoothly at room temperature leading to the corresponding adducts, which can
Reaction of Enol Ethers with Alkynes Catalyzed by Transition Metals: 5exo-dig versus 6endo-dig Cyclizations via Cyclopropyl Platinum or Gold Carbene Complexes
作者:Cristina Nevado、Diego J. Cárdenas、Antonio M. Echavarren
DOI:10.1002/chem.200204646
日期:2003.6.6
in methanol is catalyzed by electrophilic Pt(II), Pd(II), and Au(III) chlorides and by a Cu(I) complex to give five- or six-memberedrings bearing dimethyl acetals. The reaction takes place by an anti addition of the enol ether and the metal to the alkyne. The possible involvement of vinylidenecomplexes in this reaction is excluded. In addition to the usual 5-exo-dig (or 6-exo-dig) pathways, a 6-endo-dig
The role of cyclobutenes in gold(i)-catalysed skeletal rearrangement of 1,6-enynes
作者:Ana Escribano-Cuesta、Patricia Pérez-Galán、Elena Herrero-Gómez、Masaki Sekine、Ataualpa A. C. Braga、Feliu Maseras、Antonio M. Echavarren
DOI:10.1039/c2ob25419k
日期:——
electron-donating substituents at the alkyne undergo gold(I)-catalysed single cleavage skeletal rearrangement, whereas substrates with electron-withdrawing substituents evolve selectively to double cleavage rearrangement. Theoretical calculations provide a qualitative rationale for these effects, and suggest that bicyclo[3.2.0]hept-5-enes are involved as intermediates. We provide the first X-ray structural evidence
Dehydrative Cyclization of Alkynals: Vinylidene Complexes with the Cβ Incorporated into Unsaturated Five- or Six-Membered Rings
作者:María Batuecas、Luz Escalante、Miguel A. Esteruelas、Cristina García-Yebra、Enrique Oñate、Carlos Saá
DOI:10.1002/anie.201102969
日期:2011.10.4
A nice ring: The title compounds are easily prepared by dehydrativecyclization of terminal alkynals in the presence of osmium, iridium, and rhodium precursors (see scheme).
Asymmetric Total Synthesis of Twin Bufogargarizins A and B
作者:Li-Ping Zhong、Rui Feng、Jing-Jing Wang、Chuang-Chuang Li
DOI:10.1021/jacs.2c13494
日期:2023.2.1
The first and asymmetric total synthesis of bufogargarizins A and B, two unusual and highly oxygenated twin steroids with rearranged A/B rings, was achieved. The synthetically challenging [7–5–6–5] tetracyclic ring system of bufogargarizin A was efficiently constructed by the first intramolecular Ru-catalyzed [5 + 2] cycloaddition reaction of a vinyl ether cyclopropane-yne. Notably, the interesting
bufogargarizins A 和 B 是两种不寻常且高度氧化的双类固醇,具有重排的 A/B 环,首次实现了不对称全合成。通过乙烯基醚环丙烷炔的第一个分子内 Ru 催化的 [5 + 2] 环加成反应,有效地构建了具有合成挑战性的 bufogargarizin A [7-5-6-5] 四环系统。值得注意的是,有趣的 [5-7-6-5] 蟾蜍加利津 B 四环骨架通过来自 [7-5-6-5] 四环框架的独特逆醛醇/跨环醛醇级联反应非对映选择性地重新组装。