Divergent Pathways in the Intramolecular Reactions between Rhodium-Stabilized Vinylcarbenoids and Pyrroles: Construction of Fused Tropanes and 7-Azabicyclo[4.2.0]octadienes
摘要:
The rhodium(II)-catalyzed intramolecular reaction between vinyldiazomethanes and pyrroles leads to a novel synthesis of fused tropanes. The reaction occurs by a stepwise 3 + 4 annulation mechanism between a rhodium-stabilized vinylcarbenoid intermediate and the pyrrole rather than by the typical tandem cyclopropanation/Cope rearrangement sequence. The outcome of the reaction is very sensitive to the vinylcarbenoid structure. In particular, the presence of a 2-siloxy substituent on the vinylcarbenoid strongly favors the formation of fused tropanes. In the absence of such functionality, the formation of fused 7-azabicyclo[4.2.0]octadienes becomes the dominant reaction pathway.
Gold(I)‐Catalyzed Selective Cyclization and 1,2‐Shift to Prepare Pseudorutaecarpine Derivatives
作者:Wang Wang、Nan‐Ying Chen、Pei‐Sen Zou、Li Pang、Dong‐Liang Mo、Cheng‐Xue Pan、Gui‐Fa Su
DOI:10.1002/adsc.202101054
日期:2022.2.15
pseudorutaecarpine derivatives were prepared in good to excellent yields through a gold(I)-catalyzed selective cyclization and 1,2-shift of N-alkynyl quinazolinone-tethered indoles. Mechanistic study revealed that spiroindolenines generated in situ by cyclization at the the indole C3 position underwent an alkenyl 1,2-shift to generate pseudorutaecarpine. The reaction proceeds under mild reaction conditions
Stereoselective Preparation of (E)-Configured 1,2-Disubstituted Propenes from Two Aldehydes by a Two-Carbon Stitching Strategy: Convergent Synthesis of 18,21-Diisopropyl-Geldanamycin Hydroquinone and Its C7 Epimer
作者:Thomas Hampel、Thomas Neubauer、Thomas van Leeuwen、Thorsten Bach
DOI:10.1002/chem.201201600
日期:2012.8.13
The assembly of the two aldehydes was achieved employing α‐chloroethyl magnesium chloride as a two‐carbon building block. The carbenoid reagent was generated from α‐chloroethyl para‐tolylsulfoxide by sulfoxide–magnesium exchange and it added smoothly to the highly sensitive aldehyde of the Eastern fragment (C1C7). Upon oxidation, an α‐chloroethyl ketone was generated, which underwent a clean and high‐yielding
A de novo synthesis of a benzene ring allows for the preparation of a diverse range of heterocycles including indoles, benzofurans, benzothiophenes, carbazoles, and dibenzofurans from simple heteroaryl propargylic esters using a unified carbonylative benzannulation strategy. Multiple substituents can be easily introduced to the C4–C7 positions of indoles and related heterocycles.
Synthesis of Highly Substituted Pyridines via [4 + 2] Cycloadditions of Vinylallenes and Sulfonyl Cyanides
作者:Samuel G. Bartko、Phillip J. Hamzik、Leandro Espindola、Christian Gomez、Rick L. Danheiser
DOI:10.1021/acs.joc.9b02628
日期:2020.1.17
A convergent strategy for the synthesis of multisubstituted pyridines is described. Vinylallenes combine with commercially available arylsulfonyl cyanides in Diels-Alder cycloadditions to generate isopyridine cycloadducts that are converted to pyridines upon further heating or addition of a base. The 2-sulfonylpyridine products undergo nucleophilic aromatic substitution reactions with oxygen and carbon