Synthesis of Magnaldehydes B and E and Dictyobiphenyl B by Microwave‐Promoted Cross‐Coupling of Boronophenols

Abstract

Magnaldehydes B and E along with their 4′‐methylated derivatives are naturally occurring 2,4′‐biphenols that have been isolated from the Magnoliaceae. Herein, these natural products have been synthesized from a common intermediate, which was obtained by a microwave‐promoted, heterogeneously catalyzed, and protecting‐group‐free Suzuki–Miyaura coupling reaction in an aqueous medium. These reaction conditions were also successfully applied to a one‐step synthesis of the slime mold metabolite dictyobiphenyl B.

Toward a Symphony of Reactivity: Cascades Involving Catalysis and Sigmatropic Rearrangements

“…The ability to control the pathway by judicious choice of reaction conditions in any given substrate system increases the diversity of products that can be generated using a single catalyst. [53] Whereas Grubbs I catalyst, [Cl 2 (PCy 3 ) 2 Ru = CHPh], rapidly catalyzed conversion of diene 162 to the dihydrofuran 163, it was reasoned that the isomerization reactivity of the ruthenium carbene could be enhanced by formation of a ruthenium-hydride species. Schmidt and coworkers exploited Grubbs observation that [Cl 2 (PCy 3 ) 2 Ru = CHOEt] (formed by the reaction of [Cl 2 (PCy 3 ) 2 Ru = CHPh] with electron-rich olefins) decomposes to the rutheniumhydride complex [RuHCl(CO)(PCy 3 ) 2 ] upon heating.…”

Natural Products from Social Amoebae

“…A further synthesis of dictyobiphenyl B ( 37 ) was performed by Schmidt et al. (Scheme ), in which a microwave‐promoted, protecting group‐free Suzuki–Miyaura coupling was achieved in aqueous medium. In this instance, the nucleophilic and electrophilic coupling partners were reversed, when compared to the Kikuchi synthesis .…”

“…The naturalproducts Pt-1-5 (23)(24)(25)(26)(27)were obtained from methanolic extractso ff ruiting bodies of P. tenuissimum;P pc-1 (28) was obtained analogously from fruiting bodies of P. pseudocandidum (Scheme 4). [22] To confirm the structure determined by NMR studies, Pt-4 (26)w as synthesized from 5-methoxyresorcinol (29)( Scheme 4b); installation of the acyl side chain was achieved by Friedel-Crafts acylation with butanoyl chloride.…”

A One‐Pot Synthesis of Pyranocoumarins Through Microwave‐Promoted Propargyl Claisen Rearrangement/Wittig Olefination

“…[10] Over the past few years, we have contributed to the field of microwave-promoted tandem reactions with the development of a Claisen rearrangement/oxa-Michael cyclization reaction sequence for the synthesis of substituted chromones and chroman-4-ones. [11] Various 8-allyl-and prenyl-substituted coumarins have been obtained by us [12] and others [13] through a tandem sequence that involves a Claisen rearrangement of allyl phenyl ethers, a Wittig olefination, E/Z isomerization, and cyclization reactions. During a latter study, we also investigated an example of a tandem propargyl Claisen rearrangement/Wittig olefination reaction sequence (Scheme 1).…”