94829-91-1Relevant academic research and scientific papers
Total Synthesis of Caesalpinnone A and Caesalpinflavan B: Evolution of a Concise Strategy
Timmerman, Jacob C.,Sims, Noah J.,Wood, John L.
supporting information, p. 10082 - 10090 (2019/07/04)
The total syntheses of caesalpinnone A (1) and its putative biosynthetic precursor caesalpinflavan B (3) are described. Herein, we describe the evolution of a synthetic strategy toward 1 and 3, which entails a convergent Barluenga coupling that quickly delivers a heavily functionalized benzopyran containing the core carbon framework and exploration of two distinct synthetic routes for forging the flavanoid C-ring by reducing a sterically encumbered embedded alkene: one via a stepwise approach and a second, more direct and atom-economical, enabled by a Shenvi-HAT hydrogenation. The latter strategy allowed access to caesalpinflavan B in 6 steps after Pd-mediated deallylation. A late-stage dearomative phenolic oxidation and deallylation/oxa-Michael cascade was implemented to access caesalpinnone A (1) in 7 steps. We also describe an enantioselective total synthesis and stereochemical revision of (-)-caesalpinflavan B, as well as a formal enantioselective synthesis of (-)-caesalpinnone A, by implementing an enantioselective Pd-catalyzed conjugate addition developed by Stoltz.
Palladium-catalyzed asymmetric conjugate addition of arylboronic acids to heterocyclic acceptors
Holder, Jeffrey C.,Marziale, Alexander N.,Gatti, Michele,Mao, Bin,Stoltz, Brian M.
supporting information, p. 74 - 77 (2013/02/25)
Flava Flavanone: Asymmetric conjugate additions to chromones and 4-quinolones are reported utilizing a single catalyst system formed in situ from Pd(OCOCF3)2 and (S)-tBuPyOX. Notably, these reactions are performed in wet solvent under ambient atmosphere, and employ readily available arylboronic acids as the nucleophile, thus providing ready access to these asymmetric heterocycles (see scheme).
Synthetic approach to flavanones and flavones via ligand-free palladium(ii)-catalyzed conjugate addition of arylboronic acids to chromones
Kim, Donghee,Ham, Kyungrok,Hong, Sungwoo
experimental part, p. 7305 - 7312 (2012/09/22)
The remarkable catalytic effects of Fe(OTf)3 in the context of the Pd(ii)-catalyzed conjugate addition of arylboronic acids to chromones were observed to yield a variety of flavanones under mild conditions. The addition of catalytic amounts of DDQ and KNO2 to the reactions exclusively yielded flavone analogs. The reaction scope for the transformation was fairly broad, affording good yields of a wide range of flavanones and flavones, which are privileged structures in many biologically active compounds.
