Tandem Sonogashira-Hagihara Coupling/Cycloisomerization Reactions of Ethynylboronic Acid MIDA Ester to Afford 2-Heterocyclic Boronic Acid MIDA Esters: A Concise Route to Benzofurans, Indoles, Furopyridines and Pyrrolopyridines
摘要:
A one-pot process that provides direct access to 2-heterocyclic MIDA (N-methyliminodiacetic acid) boronates has been developed. The reaction of 2-iodophenols or 2-iodoanilines with ethynylboronic acid MIDA ester readily afforded 2-substituted heterocyclic compounds. Amidine and phosphazene bases, especially TMG (1,1,3,3-tetramethylguanidine) assumed an important role in the tandem Sonogashira-Hagihara coupling/cycloisomerization reactions.
Nucleophilic C–H Etherification of Heteroarenes Enabled by Base-Catalyzed Halogen Transfer
作者:Thomas R. Puleo、Danielle R. Klaus、Jeffrey S. Bandar
DOI:10.1021/jacs.1c06481
日期:2021.8.18
for the direct C–H etherification of N-heteroarenes. Potassium tert-butoxide catalyzes halogen transfer from 2-halothiophenes to N-heteroarenes to form N-heteroaryl halide intermediates that undergo tandem base-promoted alcohol substitution. Thus, the simple inclusion of inexpensive 2-halothiophenes enables regioselective oxidative coupling of alcohols with 1,3-azoles, pyridines, diazines, and polyazines
The Difluoromethyl Group as a Masked Nucleophile: A Lewis Acid/Base Approach
作者:Jacob B. Geri、Michael M. Wade Wolfe、Nathaniel K. Szymczak
DOI:10.1021/jacs.8b06093
日期:2018.8.1
that the combination of a Brønsted superbase with a weak Lewisacid enables deprotonation of Ar-CF2H groups and capture of reactive Ar-CF2- fragments. This route provides access to isolable and reactive Ar-CF2- synthons that react with a broad array of electrophiles at room temperature. The methodology is highly general in both electrophile and difluoromethyl (hetero)arene and can be applied directly
Strategy for Overcoming Full Reversibility of Intermolecular Radical Addition to Aldehydes: Tandem C–H and C–O Bonds Cleaving Cyclization of (Phenoxymethyl)arenes with Carbonyls to Benzofurans
作者:Hong-Xing Zheng、Xiang-Huan Shan、Jian-Ping Qu、Yan-Biao Kang
DOI:10.1021/acs.orglett.8b01207
日期:2018.6.1
An intermolecular addition of carbon radicals enabled by a cascade radical coupling strategy is developed. It includes an intermolecular alkyl radical addition to a carbonyl group followed by an intramolecular alkoxy radical addition to haloarenes and produces substituted benzofurans in high yields. The radical nature of this reaction is explored by radical trapping experiments and EPR analysis. The
One-pot synthesis of 2-substituted benzo[b]furans via Pd–tetraphosphine catalyzed coupling of 2-halophenols with alkynes
作者:Rong Zhou、Wei Wang、Zhi-jie Jiang、Kun Wang、Xue-li Zheng、Hai-yan Fu、Hua Chen、Rui-xiang Li
DOI:10.1039/c4cc00815d
日期:——
A catalyst composed of [Pd(η(3)-C3H5)Cl]2 and N,N,N',N'-tetra(diphenylphosphinomethyl)pyridine-2,6-diamine (L) was found to be effective for one-pot synthesis of 2-substitutedbenzo[b]furansfrom 2-halophenols and alkynes. For 2-bromo-3-hydroxypyridine, the catalyst loading could be as low as 1 ppm and the turnover number (TON) was up to 870,000.
One-pot Tandem Heck alkynylation/cyclization reactions catalyzed by Bis(Pyrrolyl)pyridine based palladium pincer complexes
作者:Seema Yadav、Chandrakanta Dash
DOI:10.1016/j.tet.2020.131350
日期:2020.7
Ligand assisted palladium catalyzed one-pot tandem Heck alkynylation/cyclization reactions for the synthesis of benzofurans was reported in this paper. Well-defined palladium-pincer complexes exhibited excellent catalytic activities for the one-pot tandem Heck alkynylation/cyclization reactions yielding benzofuran derivatives using 0.1 mol% catalyst. All the catalyticreactions are performed in air