Exploiting the dual role of ethynylbenziodoxolones in gold-catalyzed C(sp)–C(sp) cross-coupling reactions
作者:Somsuvra Banerjee、Nitin T. Patil
DOI:10.1039/c7cc04283c
日期:——
Reported herein is the gold-catalyzed alkynylation of terminal alkynes using ethynylbenziodoxolones (EBXs), where EBXs serve a dual role as oxidants as well as alkyne transfer agents to access unsymmetrical 1,3-diynes. Hence, the catalytic system requires no externaloxidants and is compatible with a broad range of substrates, including those with polar functional groups such as NH, OH and B(OH)2.
Friedel–Crafts alkylations of electron-rich aromatics with 3-hydroxy-2-oxindoles: scope and limitations
作者:Lakshmana K. Kinthada、Santanu Ghosh、K. Naresh Babu、Mohd. Sharique、Soumava Biswas、Alakesh Bisai
DOI:10.1039/c4ob01264j
日期:——
A Lewis acid-catalyzed nucleophilic addition of electron rich aromatics with 3-hydroxy-2-oxindoles 5 was developed. The reaction is believed to proceed through the 2H-indol-2-one ring system 9, which eventually reacts with various electron-rich aromatics to afford a variety of 2-oxindoles with an all-carbon quaternary center at the pseudobenzylic position (4, 8, 13, and 16) in high yields. The methodology provides an expeditious route to the tetracyclic core (3) of diazonamide (1), and azonazine (2) as well as the tricyclic core of asperazine (6a), idiospermuline (6b), and calycosidine (6c) viz. C(3a)-arylpyrroloindolines 7 having an all-carbon quaternary center on further synthetic elaboration.
Lewis acid-catalyzed Friedel–Crafts alkylations of 3-hydroxy-2-oxindole: an efficient approach to the core structure of azonazine
作者:Santanu Ghosh、Lakshmana K. Kinthada、Subhajit Bhunia、Alakesh Bisai
DOI:10.1039/c2cc35283d
日期:——
A Lewis acid catalyzed FriedelâCrafts reaction of electron rich aromatics with 3-alkyl-3-hydroxy-2-oxindole (5) has been developed. The methodology provides a straightforward access to the core of azonazine (2) sharing an all-carbon quaternary stereocenter at the tetracyclic ring junction.
Selective monoethynylation of isatins using solid calcium carbide as a surrogate of gaseous acetylene
作者:Runze Qi、Zheng Li
DOI:10.1080/00397911.2022.2139187
日期:2022.12.2
Abstract Highly selective monoethynylation of isatins using solid calcium carbide as a surrogate of gaseous acetylene was described. A series of multifunctional compounds, 3-ethynyl-3-hydroxyindolin-2-ones, were efficiently synthesized at room temperature through a one-step procedure. The salient features of this protocol are the use of inexpensive and easy-to-handle solid alkyne sources instead of
Kinetic Resolution of Tertiary Alcohols by Chiral DMAP Derivatives: Enantioselective Access to 3-Hydroxy-3-substituted 2-Oxindoles
作者:Hiroki Mandai、Ryuhei Shiomoto、Kazuki Fujii、Koichi Mitsudo、Seiji Suga
DOI:10.1021/acs.orglett.0c03956
日期:2021.2.19
We developed an efficient acylative kineticresolution of 3-hydroxy-3-substituted 2-oxindoles by a chiral DMAP derivative having a 1,1′-binaphthyl with two tert-alcohols units. A wide range of 3-hydroxy-3-substitutedoxindoles having various functional groups were efficiently resolved (14 examples, up to s = 60) in the presence of 1 mol % of catalyst within 3–9 h. Multigram-scale reactions (10 g) also