Regioselective reductive opening of substituted phthalans: synthetic applications
摘要:
The reductive opening of substituted phthalans 6, 11, 12, 20, 21 and 28 with lithium and a catalytic amount of DTBB leads to the formation of corresponding functionalised organolithium intermediates 8, 15, 16, 23, 25 and 29+30 in a regioselective manner. The further reaction of these dianions with different electrophiles, mainly carbonyl compounds, gives the expected functionalised benzylic alcohols 9, 17, 18, 24, 26 and 31+32. The observed stereochemistry can be easily explained taking into account the values of the electron densities deduced by semiempirical PM3 calculations. (c) 2008 Elsevier Ltd. All rights reserved.
The solvent‐ and ligand‐free [2+2+2] ruthenium‐promoted cycloaddition of α,ω‐diynes and alkynes provides a facile and efficient strategy for the synthesis of substituted benzene‐derived systems. The search for the optimal reaction conditions revealed the unprecedented catalytic activity of ruthenium trichloride for benzannulation reactions and this atom‐economical process allowed the synthesis of fused
Photoinduced Ligand-to-Metal Charge Transfer Enables Photocatalyst-Independent Light-Gated Activation of Co(II)
作者:Benjamin D. Ravetz、Jason Y. Wang、Kyle E. Ruhl、Tomislav Rovis
DOI:10.1021/acscatal.8b04326
日期:2019.1.4
Photoredoxcatalysis can be used to manipulate the redox state of a transitionmetalcomplex leading to the desired reactivity. While powerful, obviating the role of the second catalyst would be attractive from the perspective of simplifying the protocol and using visible light to uncover unexpected, enabling reactivity. Herein we report that Co-acetylides, formed in situ, are photoactive complexes
combination of cationic rhodium(I) complexes with N-phosphino tert-butylsulfinamides (PNSO) ligands is efficient for catalytic intra- and intermolecular [2+2+2] cycloaddition reactions. PNSO ligands are a new class of chiral bidentate ligands, which have the characteristic of combining the easily accessible sulfur chirality with the coordinating capacity of phosphorous. Cycloaddition of open-chained and
simply performed procedure for the [Rh(cod)Cl]2/cationic 2,2′-bipyridyl system-catalyzed [2+2+2] cycloaddition of α,ω-diynes with terminal and internal alkynes was achieved in waterunderair at 60 °C. The reaction proceeded smoothly with 1 equiv α,ω-diynes and 3 equiv alkynes in the presence of 20 mol % KOH for 1 h or 9 h, resulting in the formation of tri- and tetra-substituted benzene derivatives in
of dienynes was investigated using cobalt-based catalysts. Substrates without substitution on alkyne moiety were found to react under thermal activation. The use of a cobalt salt as catalyst made reactions cleaner by limiting the formation of byproducts. Cycloadditions with dienynes possessing a substituent on the alkyne pattern occurred only in presence of a cobalt catalyst which displayed a moderate