72398-76-6Relevant academic research and scientific papers
8,10,12 as nanoreactors for non-enzymatic introduction of: Ortho, meta or para -hydroxyl groups to aromatic molecules
Bahrami, Mozhgan,Zhang, Xingwen,Ehsani, Morteza,Jahani, Yousef,Laine, Richard M.
supporting information, p. 8797 - 8808 (2017/07/22)
Traditional electrophilic bromination follows long established "rules": electron-withdrawing substituents cause bromination selective for meta positions, whereas electron-donating substituents favor ortho and para bromination. In contrast, in the [PhSiO1.5]8,10,12 silsesquioxanes, the cages act as bulky, electron withdrawing groups equivalent to CF3; yet bromination under mild conditions, without a catalyst, greatly favors ortho substitution. Surprisingly, ICl iodination without a catalyst favors (>90%) para substitution [p-IC6H4SiO1.5]8,10,12. Finally, nitration and Friedel-Crafts acylation and sulfonylation are highly meta selective, >80%. In principle, the two halogenation formats coupled with the traditional electrophilic reactions provide selective functionalization at each position on the aromatic ring. Furthermore, halogenation serves as a starting point for the synthesis of two structural isomers of practical utility, i.e. in drug prospecting. The o-bromo and p-iodo compounds are easily modified by catalytic cross-coupling to append diverse functional groups. Thereafter, F-/H2O2 treatment cleaves the Si-C bonds replacing Si with OH. This represents a rare opportunity to introduce hydroxyl groups to aromatic rings, a process not easily accomplished using traditional organic synthesis methods. The as-produced phenol provides additional opportunities for modification. Each cage can be considered a nanoreactor generating 8-12 product molecules. Examples given include syntheses of 4,2′-R,OH-stilbenes and 4,4′-R,OH-stilbenes (R = Me, CN). Unoptimized cleavage of the Br/I derivatives yields 55-85% phenol. Unoptimized cleavage of the stilbene derivatives yields 35-40% (3-5 equivalents of phenol) in the preliminary studies presented here. In contrast, meta R-phenol yields are 80% (7-10 mol per cage).
One-Step Synthesis of Substituted Benzofurans from ortho- Alkenylphenols via Palladium-Catalyzed C=H Functionalization
Yang, Dejun,Zhu, Yifei,Yang, Na,Jiang, Qiangqiang,Liu, Renhua
, p. 1731 - 1735 (2016/06/09)
A dehydrogenative oxygenation of C(sp2)=H bonds with intramolecular phenolic hydroxy groups has been developed, which provides a straightforward and concise access to structurally diversely benzofurans from ortho-alkenylphenols. The reaction is catalyzed by palladium on carbon (Pd/C) without any oxidants and sacrificing hydrogen acceptors.
