Catalytic Availabilities of Lewis Acidic SnCl<sub>2</sub>: Ph<sub>3</sub>PAuCl-SnCl<sub>2</sub>Composite Catalyzed Successive<i>ortho</i>-Alkenylation/O-Alkenylation of Phenols Followed by Cyclization to 1-Benzopyrans
Ph3PAuCl and SnCl2, catalyzed the formation of 1-benzopyrans from phenols and phenylacetylene. The Ph3PAuCl–SnCl2 composite catalyzed reaction was presumed to proceed through the successive ortho-alkenylation and O-alkenylation of phenols with phenylacetylene followed by cyclization of the prepared ortho- and O-dialkenylated phenol derivatives. Conveniently, all reactions with Ph3PAuCl–SnCl2 composite
Phenols were vinylated at the ortho-position with ethyne in the presence of SnCl(4)-Bu(3)N reagent. The reaction was applicable to phenols possessing either electron-donating or electron-withdrawing groups. 2,6-Divinylphenols were synthesized under modified conditions. A reaction mechanism involving carbostannylation of alkynyltin and phenoxytin was discussed.
B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>-Catalyzed Sequential Additions of Terminal Alkynes to <i>para</i>-Substituted Phenols: Selective Construction of Congested Phenol-Substituted Quaternary Carbons
作者:Hui Chen、Mo Yang、Guoqiang Wang、Liuzhou Gao、Zhigang Ni、Jingxiang Zou、Shuhua Li
DOI:10.1021/acs.orglett.1c01863
日期:2021.7.16
We have developed a borane-catalyzed sequential addition of terminal alkynes to para-substitutedphenols, which affords a wide range of ortho-propargylic alkylated phenols bearing congested quaternary carbons. Control experiments combined with DFT calculations suggest that the reaction undergoes a sequential phenol alkenylation/hydroalkynylation process. Further extension of this strategy to the construction
B(C
<sub>6</sub>
F
<sub>5</sub>
)
<sub>3</sub>
‐Catalyzed Hydroarylation of Aryl Alkynes for the Synthesis of 1,1‐Diaryl and Triaryl Substituted Alkenes
作者:Hui Chen、Liuzhou Gao、Xueting Liu、Guoqiang Wang、Shuhua Li
DOI:10.1002/ejoc.202101001
日期:2021.10.7
B(C6F5)3-catalyzed hydroarylation of both terminal and internal alkynes leads to 1,1-diaryl and triaryl substituted alkenes. A B(C6F5)3-phenol adduct mediated protonation mechanism is responsible for the formation of the related alkenes as well as the observed stereoselectivity.
B(C 6 F 5 ) 3 -催化的末端和内部炔烃的加氢芳基化产生1,1-二芳基和三芳基取代的烯烃。AB(C 6 F 5 ) 3 -苯酚加合物介导的质子化机制负责相关烯烃的形成以及观察到的立体选择性。
Transition-Metal-Free Lactonization of sp<sup>2</sup> C–H Bonds with CO<sub>2</sub>
The transition-metal-free lactonization of heteroaryl and alkenyl C–H bonds with carbon dioxide is reported to synthesize important coumarin derivatives in moderate to excellent yields. These redox-neutral reactions feature a broad substrate scope, good functional group tolerance, facile scalability, and easy product derivatization.