2<i>H</i>-Chromenes Generated by an Iron(III) Complex-Catalyzed Allylic Cyclization
作者:L. Calmus、A. Corbu、J. Cossy
DOI:10.1002/adsc.201500058
日期:2015.5.4
A straightforward method based on an iron(III) complex‐catalyzed cyclization of 2‐(1‐hydroxyallyl)phenols is reported to access a large variety of 2H‐chromenes. This method was applied to the total synthesis of a natural product, tephrowatsin B.
A three‐component palladium‐catalyzed reaction sequence has been developed in which γ‐substituted α,β‐unsaturated products are obtained in a single flask by an α‐alkenylation with either a subsequent γ‐alkenylation or γ‐arylation of a ketoneenolate. Coupling of a variety of electronically and structurally different components was achieved in the presence of a Pd/Q‐Phos catalyst (2 mol %), usually
Application of Vinyl Nucleophiles in Matteson Homologations
作者:Thorsten Kinsinger、Uli Kazmaier
DOI:10.1021/acs.orglett.2c01119
日期:2022.5.27
nucleophiles was found to be a versatile tool for the synthesis of highly substituted and functionalized allyl boronic esters. High yields and stereoselectivities are obtained with sterically demanding alkyl boronic esters and/or Grignard reagents. With the application of such vinyl Matteson homologations, the polyketide fragment of lagunamide B is synthesized.
发现与乙烯基亲核试剂的 Matteson 同系化是合成高度取代和功能化的烯丙基硼酸酯的通用工具。使用空间要求高的烷基硼酸酯和/或格氏试剂可获得高产率和立体选择性。通过应用这种乙烯基 Matteson 同系物,合成了 lagunamide B 的聚酮化合物片段。
Concise, Convergent Syntheses of (±)-Trichostatin A Utilizing a Pd-Catalyzed Ketone Enolate α-Alkenylation Reaction
作者:Casey C. Cosner、Paul Helquist
DOI:10.1021/ol200964m
日期:2011.7.15
Two concise, convergent syntheses of (+/-)-trichostatin A (1), a potent histone deacetylase inhibitor, have been accomplished. The key step in both is a Pd-catalyzed alpha-alkenylation reaction between ketone 2 and either dienyl bromide 3 or alkenyl bromide 9 using a modification of cross-coupling conditions described by Negishi and Hartwig. A brief investigation has shown the potential utility of a Ni-catalyzed version of this reaction. The overall synthetic routes are short and amenable to scaleup, providing access to trichostatin A via trichostatic acid as a direct precursor.
Ni-Catalyzed Alkenylation of Ketone Enolates under Mild Conditions: Catalyst Identification and Optimization
A procedure for Ni-catalyzed cross-coupling of ketone enolates with alkenyl halides has been developed. Intermolecular coupling of aromatic and aliphatic ketone lithium enolates with a variety of alkenyl halides is achieved in the presence of Ni(cod)(2) catalyst (5 mol %), an N-heterocyclic carbene (NHC) ligand, and LiI (10 mol %) at 6-22 degrees C for 0.5-12 h with yields of up to 90%. During the initial development of this reaction, a misleading result with respect to the actual active catalyst was obtained using commercially available Q:Phos ligand, which was found to contain a trace of Pd metal contaminant sufficient to catalyze the reaction. However, under the final conditions optimized for Ni(cod)(2) in the presence of an NHC ligand, Pd was incompetent as a catalyst.