Combining Silver Catalysis and Organocatalysis: A Sequential Michael Addition/Hydroalkoxylation One-Pot Approach to Annulated Coumarins
摘要:
A highly stereoselective one-pot procedure for the synthesis of five-membered annulated hydroxycoumarins has been developed. By merging primary amine catalysis with silver catalysis, a series of functionalized coumarin derivatives were obtained in good yields (up to 91%) and good to excellent enantioselectivities (up to 99% ee) via a Michael addition/hydroalkoxylation reaction. Depending on the substituents on the enynone, the synthesis of annulated six-membered rings is also feasible.
report transition-metal-catalyzed B-H bond insertion reactions between borane adducts and alkynes to afford organoboron compounds in excellent yields under mild reaction conditions. This successful use of alkynes as carbene precursors in these reactions constitutes a new route to organoboron compounds. The startingmaterials are safe and readily available, and the reaction exhibits 100% atom-economy
Enantioselective Synthesis of Allenes by Catalytic Traceless Petasis Reactions
作者:Yao Jiang、Abdallah B. Diagne、Regan J. Thomson、Scott E. Schaus
DOI:10.1021/jacs.6b11937
日期:2017.2.8
Allenes are useful functional groups in synthesis as a result of their inherent chemical properties and established reactivity patterns. One property of chemical bonding renders 1,3-substituted allenes chiral, making them attractive targets for asymmetric synthesis. While there are many enantioselective methods to synthesize chiral allenes from chiral starting materials, fewer methods exist to directly
Linear Conjugated Systems Bearing Aromatic Terminal Groups. III. The Synthesis and the Electronic Spectra of 1,1′-Dinaphthyl- and 2,2′-Dinaphthylpoly-ynes
1,1′-Dinaphthylpoly-ynes (In, n=1–6) and 2,2′-dinaphthylpoly-ynes (IIn, n=1–6) were synthesized, and their electronic spectra were measured. The In-series gave an excellent agreement with the λmax∝n1.5 relationship, and the IIn-series followed a straight line, λmax∝n1.3. These relationships are different from those of 1,1′-dianthryl- and 9,9′-dianthrylpory-ynes, in which the plots of λmax versus n2 give excellent straight lines (Bull. Chem. Soc. Jap., 39, 2320 (1966); 40, 340 (1967)). The new linear relationships found in the dinaphthyl-series offer further evidence of the prominent effect of the terminal groups upon the electronic spectral properties of the conjugated poly-yne system.
Ag-Catalyzed Insertion of Alkynyl Carbenes into C–C Bonds of β-Ketocarbonyls: A Formal C(sp<sup>2</sup>) Insertion
作者:Yongquan Ning、Qingmin Song、Paramasivam Sivaguru、Lizuo Wu、Edward A. Anderson、Xihe Bi
DOI:10.1021/acs.orglett.1c04081
日期:2022.1.21
Here we report a silver-catalyzed alkynyl carbene insertion into β-ketocarbonyls using alkynyl N-nosylhydrazones as alkynyl carbene precursors, which provides access to trisubstituted allenyl ketones. This reaction represents the first example of an alkynyl carbene insertion into a C–C σ bond, affording products homologated with an sp2 carbon center. The products are useful substrates for further transformations
Highly Regio- and Stereoselective Synthesis of <i>Z</i> and <i>E</i> Enol Esters by an Amine-Catalyzed Conjugate Addition–Rearrangement Reaction of Ynals with Carboxylic Acids
作者:He Huang、Xinshuai Zhang、Chenguang Yu、Xiangmin Li、Yueteng Zhang、Wei Wang
DOI:10.1021/acscatal.6b02206
日期:2016.12.2
The broad synthetic utility of labile enolesters demands efficient methods for the stereo- and regioselectivesynthesis of both Z and E isomers. The available synthetic methods dominated by metal catalysis cannot meet the challenge. We wish to report a metal-free organocatalytic divergent approach to both E and Z isomers of enolesters from the same reactant pools with the same catalytic system. A