4254-67-5Relevant articles and documents
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Reznikov,V.M.,Novitskii,V.F.
, (1975)
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Stereoselective Formation of β-O-4 Structures Mimicking Softwood Lignin Biosynthesis: Effects of Solvent and the Structures of Quinone Methide Lignin Models
Zhu, Xuhai,Akiyama, Takuya,Yokoyama, Tomoya,Matsumoto, Yuji
, (2019)
p-Quinone methide (QM) is formed as an intermediate during lignin biosynthesis. The aromatization of the QM by the attack of a nucleophile at the α-position of its side chain generates a phenolic hydroxy group in a growing polymer and creates stereoisomeric forms in the side chain. A series of β-O-4-aryl ether QMs was reacted with water at 25 °C to replicate the formation of p-hydroxyphenyl (H) and guaiacyl (G) β-O-4 structures in plant cell walls. Water addition occurred in 3-methoxy-substituted QMs (G-type QMs) with half-lives (t1/2) between 13 and 15 min, at pH 7, in 50% water solution (dioxane-water, 1:1). The rate increased as the water concentration increased to 99% (t1/2, 1.2-1.4 min). Similar solvent effects were observed for more reactive nonsubstituted QMs (H-type QMs with t1/2 of 1/2 of the H-type QMs was shorter than that of the G-type QMs under every solvent condition. Upon increasing the water concentration, the variation in the erythro/threo ratios of the four dimeric β-O-4 products increased. Interestingly, the effect of pH on the stereopreference, which was observed in 50% water solution, was small and became imperceptible as the water concentration increased to 99%, suggesting that the effect of the solvent, as well as the effect of the pH, plays an important role in understanding the reaction conditions in cell walls during lignin biosynthesis. The threo isomer was preferentially formed in the four dimeric β-O-4 structures, which is inconsistent with the structural features of compression wood lignin rich in H-units. However, the erythro-selective formation was attained in an H-type QM at every pH studied (pH 3.5-7) by introducing a biphenyl structure into the β-etherified ring moiety.
Benzoic acid resin (BAR): a heterogeneous redox organocatalyst for continuous flow synthesis of benzoquinones from β-O-4 lignin models
Dias, Kevin de Aquino,Pereira Junior, Marcus Vinicius Pinto,Andrade, Leandro Helgueira
supporting information, p. 2308 - 2316 (2021/04/07)
A polymer-bound organocatalyst for Baeyer-Villiger reaction and phenol oxidation under continuous flow conditions is described for the first time.BARhas revealed two catalytic activities that enabled the generation of a novel approach for the synthesis of benzoquinones from β-O-4 lignin models in a one-pot protocol. High catalytic activities (yields up to 98%), selectivities, recyclability and productivity were achieved.
Pd-Catalyzed Decarboxylative Olefination: Stereoselective Synthesis of Polysubstituted Butadienes and Macrocyclic P-glycoprotein Inhibitors
Chen, Xiangyang,Hao, Jiping,Houk, K. N.,Li, Yingzi,Lou, Liguang,Quan, Haitian,Song, Bichao,Wang, Lu,Xia, Yuanzhi,Xie, Peipei,Xu, Zhongliang,Yang, Weibo
supporting information, p. 9982 - 9992 (2020/06/27)
The efficient and stereoselective synthesis of polysubstituted butadienes, especially the multifunctional butadienes, represents a great challenge in organic synthesis. Herein, we wish to report a distinctive Pd(0) carbene-initiated decarboxylative olefination approach that enables the direct coupling of diazo esters with vinylethylene carbonates (VECs), vinyl oxazolidinones, or vinyl benzoxazinones to afford alcohol-, amine-, or aniline-containing 1,3-dienes in moderate to high yields and with excellent stereoselectivity. This protocol features operational simplicity, mild reaction conditions, a broad substrate scope, and gram-scalability. Notably, a structurally unique allylic Pd(II) intermediate was isolated and characterized. DFT calculation and control experiments demonstrated that a rare Pd(0) carbene intermediate could be involved in this reaction. Moreover, the polysubstituted butadienes as novel building blocks were unprecedentedly assembled into macrocycles, which efficiently inhibited the P-glycoprotein and dramatically reversed multidrug resistance in cancer cells by 190-fold.
