- Copper-Catalyzed Asymmetric Diyne Cyclization via [1,2]-Stevens-Type Rearrangement for the Synthesis of Chiral Chromeno[3,4-c]pyrroles
-
Here, we report a copper-catalyzed asymmetric cascade cyclization/[1,2]-Stevens-type rearrangement via a non-diazo approach, leading to the practical and atom-economic assembly of various valuable chiral chromeno[3,4-c]pyrroles bearing a quaternary carbon
- Hong, Feng-Lin,Hong, Pan,Lu, Xin,Shi, Chong-Yang,Ye, Long-Wu,Zhai, Tong-Yi,Zhu, Xin-Qi
-
-
- A Hg(OTf)2-Catalyzed Enolate Umpolung Reaction Enables the Synthesis of Coumaran-3-ones and Indolin-3-ones
-
The potential of mercury catalysis has been extended to the arena of enolate umpolung reactions for the first time by the generation of enolonium species via Hg(OTf)2-catalyzed N-oxide addition to alkynes. The enolonium species formed can undergo intramolecular nucleophilic attack by hydroxyl or amino groups, leading to the synthesis of various coumaran-3-ones and indolin-3-ones.
- Dai, Ning,Hu, Weican,Qian, Guoying,Rong, Zhouting
-
supporting information
p. 3286 - 3290
(2020/04/21)
-
- Catalytic Transformations of Alkynes into either α-Alkoxy or α-Aryl Enolates: Mannich Reactions by Cooperative Catalysis and Evidence for Nucleophile-Directed Chemoselectivity
-
The catalytic formation of gold enolates from alkynes, nitrones, and nucleophiles is described, and their Mannich reactions result in nucleophile-directed chemoselectivity through cooperative catalysis. For 1-alkyn-4-ols and 2-ethynylphenols, their gold-catalyzed nitrone oxidations afforded N-containing dihydrofuran-3(2H)-ones with syn selectivity. The mechanism involves the Mannich reactions of gold enolates with imines through an O-H-N hydrogen-bonding motif. For aryloxyethynes, their gold enolates react selectively with nitrones to deliver 3-alkylidenebenzofuran-2-ones, as controlled by a C-H-O hydrogen-bonding motif.
- Sahani, Rajkumar Lalji,Patil, Manoj D.,Wagh, Sachin Bhausaheb,Liu, Rai-Shung
-
supporting information
p. 14878 - 14882
(2018/10/15)
-
- Cyclization of gold acetylides: Synthesis of vinyl sulfonates via gold vinylidene complexes
-
Differently substituted terminal alkynes that bear sulfonate leaving groups at an appropriate distance were converted in the presence of a propynyl gold(I) precatalyst. After initial formation of a gold acetylide, a cyclization takes place at the β-carbon atom of this species. Mechanistic studies support a mechanism that is related to that of dual gold-catalyzed reactions, but for the new substrates, only one gold atom is needed for substrate activation. After formation of a gold vinylidene complex, which forms a tight contact ion pair with the sulfonate leaving group, recombination of the two parts delivers vinyl sulfonates, which are valuable targets that can serve as precursors for cross-coupling reactions, for example. Gold vinylidene intermediates are generated by the cyclization of gold acetylides that carry a sulfonate leaving group. This result demonstrates for the first time that the formation of these species is not restricted to a dual activation mode. The cyclization products obtained herein contain a vinyl sulfonate moiety, which makes them useful building blocks for cross-coupling reactions.
- Bucher, Janina,Wurm, Thomas,Nalivela, Kumara Swamy,Rudolph, Matthias,Rominger, Frank,Hashmi, A. Stephen K.
-
supporting information
p. 3854 - 3858
(2014/05/06)
-
- OPHTHALMIC LENS MATERIALS CONTAINING CHROMOPHORES THAT ABSORB BOTH UV AND SHORT WAVELENGTH VISIBLE LIGHT
-
Chromophores that absorb both UV and short wavelength visible light are disclosed. The chromophores are particularly suitable for use in intraocular lens materials.
- -
-
Page/Page column 2; 4
(2009/03/07)
-
- Palladium-catalyzed reaction of o-ethynylphenols, o-((trimethylsilyl)ethynyl)phenyl acetates, and o-alkynylphenols with unsaturated triflates or halides: A route to 2-substituted-, 2,3-disubstituted-, and 2-substituted-3-acylbenzo[b]furans
-
The reaction of o-ethynylphenols 3 with a wide variety of unsaturated halides or triflates 6 in the presence of Pd(OAc)2(PPh3)2, CuI, and Et3N (procedure A) gives 2-vinyl- and 2-arylbenzo[b]furans 7, in good to high yield, through a palladium-catalyzed coupling followed by an in situ cyclization step. Small amounts of 2,3-disubstituted-benzo[b]furans 8 are usually isolated as side products. In some cases, however, compounds 8 are generated in significant yield or even as the main products. The formation of 8 can be prevented by employing alternative procedures (B and C) that use o-((trimethylsilyl)ethynyl)phenyl acetates 5 as starting building blocks. Procedure B is based on the palladium-catalyzed reaction of 5 with 6 in the presence of Pd(PPh3)4, Et3N, and n-Bu4NF, followed by the hydrolysis of the resultant coupling derivative 12 under basic conditions. Procedure C affords 7 through an in situ coupling cyclization of 5 with 6 in the presence of Pd(PPh3)4 and KOBu(t). The utilization of o-alkynylphenols 9 as the starting alkynes in the palladium-catalyzed reaction with 6 leads to the formation of 2,3-disubstituted-benzo[b]furans 13 through an annulation process promoted by σ-vinyl- and σ-arylpalladium complexes generated in situ. The best results in this case are obtained by using KOAc and Pd(PPh3)4. In the presence of KOAc and Pd(PPh3)4, and under an atmosphere of carbon monoxide, the reaction of o-alkynylphenols with 6 provides 2-vinyl- and 2-aryl-3-acylbenzo[b]furans 14.
- Arcadi,Cacchi,Del Rosario,Fabrizi,Marinelli
-
p. 9280 - 9288
(2007/10/03)
-