109765-60-8Relevant articles and documents
Elucidating the Role of the Boronic Esters in the Suzuki-Miyaura Reaction: Structural, Kinetic, and Computational Investigations
Thomas, Andy A.,Zahrt, Andrew F.,Delaney, Connor P.,Denmark, Scott E.
, p. 4401 - 4416 (2018)
The Suzuki-Miyaura reaction is the most practiced palladium-catalyzed, cross-coupling reaction because of its broad applicability, low toxicity of the metal (B), and the wide variety of commercially available boron substrates. A wide variety of boronic acids and esters, each with different properties, have been developed for this process. Despite the popularity of the Suzuki-Miyaura reaction, the precise manner in which the organic fragment is transferred from boron to palladium has remained elusive for these reagents. Herein, we report the observation and characterization of pretransmetalation intermediates generated from a variety of commonly employed boronic esters. The ability to confirm the intermediacy of pretransmetalation intermediates provided the opportunity to clarify mechanistic aspects of the transfer of the organic moiety from boron to palladium in the key transmetalation step. A series of structural, kinetic, and computational investigations revealed that boronic esters can transmetalate directly without prior hydrolysis. Furthermore, depending on the boronic ester employed, significant rate enhancements for the transfer of the B-aryl groups were observed. Overall, two critical features were identified that enable the transfer of the organic fragment from boron to palladium: (1) the ability to create an empty coordination site on the palladium atom and (2) the nucleophilic character of the ipso carbon bound to boron. Both of these features ultimately relate to the electron density of the oxygen atoms in the boronic ester.
Synthesis of glaziovianin A: A potent antitumor isoflavone
Hayakawa, Ichiro,Ikedo, Akiyuki,Kigoshi, Hideo
, p. 1382 - 1383 (2008/03/18)
Glaziovianin A (1) is a novel isoflavone derivative isolated from the leaves of the Brazilian tree Astelia glazioviana. Glaziovianin A (1) showed cytotoxic activity and was suggested to be an inhibitor of tubulin polymerization. We achieved the total synt
The Structure and Synthesis of Nepenthone-A, a Naphthoquinone from Nepenthes rafflesiana
Rizzacasa, Mark A.,Sargent, Melvyn V.
, p. 2017 - 2022 (2007/10/02)
The structure of a naphthoquinone, nepenthone-A, isolated from Nepenthes rafflesiana Jack, is shown to be 4,7-dihydroxy-9-methoxy-6-methylnaphto-1,3-dioxole-5,9-dione (6), firs by the synthesis of its di-O-methyl derivative (7), and then by synthesis of the natural product.
