scholarly journals A [3+2] Cyclization of Siloxyalkynes and Isocyanides for the Synthesis of Oxazoles

Synlett ◽  
2018 ◽  
Vol 30 (04) ◽  
pp. 515-518
Author(s):  
An Wu ◽  
Jianwei Sun
Keyword(s):  
Catalytic System ◽  
Mechanistic Studies ◽  
Cyclization Reactions ◽  
Aromatic Heterocycles ◽  
Mechanistic Insight

A mild and efficient [3+2] cyclization of siloxyalkynes for the synthesis of aromatic heterocycles is developed. It is a new addition to the cyclization reactions of these versatile species. In the presence of TBAF as promoter, siloxyalkynes react with electron-withdrawing isocyanides to form a range of oxazole products. In this reaction, siloxyalkynes contribute the C–O unit for the cyclization, which is different from previous typical examples where it is a two-carbon contributor. Mechanistic studies provided insights into the mechanism, which involves a ketene intermediate. Based on the mechanistic insight, an alternative catalytic system was also demonstrated to be effective for the same transformation.

Mechanistic Study and Development of Catalytic Reactions of Sm(II)

2018 ◽  
Author(s):  
Sandepan Maity ◽  
Robert Flowers
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Proton Donor ◽  
Catalytic Reactions ◽  
Mechanistic Study ◽  
Mechanistic Studies ◽  
Cyclization Reactions ◽  
Mechanistic Approach ◽  
Donor Source

Despite the broad utility and application of SmI<sub>2</sub>in synthesis, the reagent is used in stoichiometric amounts and has a high molecular weight, resulting in a large amount of material being used for reactions requiring one or more equivalents of electrons. We report mechanistic studies on catalytic reactions of Sm(II) employing a terminal magnesium reductant and trimethyl silyl chloride in concert with a non-coordinating proton donor source. Reactions using this approach permitted reductions with as little as 1 mol% Sm. The mechanistic approach enabled catalysis employing HMPA as a ligand, facilitating the development of catalytic Sm(II) 5-<i>exo</i>-<i>trig </i>ketyl olefin cyclization reactions.

Silver-Catalyzed Decarboxylative Radical Relay Difluoroalkylation-Carbocyclization: Convenient Access to CF2-Containing Quinolinones

2021 ◽  
Author(s):  
Feng Zhao ◽  
Sa Guo ◽  
Yan Zhang ◽  
Ting Sun ◽  
Xin Wang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Mechanistic Studies ◽  
Convenient Access

We report a practical Ag-catalyzed decarboxylative difluoroalkylation–carbocyclization reaction. Various structurally diverse gem-fluorinated quinolinones were obtained in moderate to good yields. Mechanistic studies suggested that the catalytic system involved a formal...

Multicomponent diversity-oriented synthesis of symmetrical and unsymmetrical 1,4-dihydropyridines in recyclable glycine nitrate (GlyNO3) ionic liquid: a mechanistic insight using Q-TOF, ESI-MS/MS

RSC Advances ◽  
2014 ◽  
Vol 4 (37) ◽  
pp. 19111-19121 ◽  
Author(s):  
Rajesh Kumar ◽  
Nitin H. Andhare ◽  
Amit Shard ◽  
Richa Richa ◽  
Arun Kumar Sinha
Keyword(s):  
Ionic Liquid ◽  
Mechanistic Studies ◽  
Diversity Oriented Synthesis ◽  
Esi Ms ◽  
Mechanistic Insight

Glycine nitrate (GlyNO3) ionic liquid has been explored for the synthesis of symmetrical and unsymmetrical 1,4-DHPs in good-to-excellent yields with mechanistic studies using Q-TOF and ESI-MS/MS.

scholarly journals Rhodium-Catalyzed Oxidative Annulation of 2- or 7-Arylindoles with Alkenes/Alkynes Using Molecular Oxygen as the Sole Oxidant Enabled by Quaternary Ammonium Salt

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5329
Author(s):  
Weihui Zhuang ◽  
Jiaqi Zhang ◽  
Yanping Zheng ◽  
Qiufeng Huang
Keyword(s):  
Molecular Oxygen ◽  
Ammonium Salt ◽  
Catalytic System ◽  
Quaternary Ammonium ◽  
Atmospheric Pressure ◽  
Quaternary Ammonium Salt ◽  
Michael Reaction ◽  
Mechanistic Studies ◽  
Dehydrogenative Coupling

Developing an efficient catalytic system using molecular oxygen as the oxidant for rhodium-catalyzed cross-dehydrogenative coupling remains highly desirable. Herein, rhodium-catalyzed oxidative annulation of 2- or 7-phenyl-1H-indoles with alkenes or alkynes to assemble valuable 6H-isoindolo[2,1-a]indoles, pyrrolo[3,2,1-de]phenanthridines, or indolo[2,1-a]isoquinolines using the atmospheric pressure of air as the sole oxidant enabled by quaternary ammonium salt has been accomplished. Mechanistic studies provided evidence for the fast intramolecular aza-Michael reaction and aerobic reoxidation of Rh(I)/Rh(III), facilitated by the addition of quaternary ammonium salt.

scholarly journals Synthesis of 1,5-Functionalized 1,2,3-Triazoles Using Ionic Liquid/Iron(III) Chloride as Efficient and Reusable Homogeneous Catalyst

2018 ◽  
Author(s):  
Antonio De Nino ◽  
Pedro Merino ◽  
Vincenzo Algieri ◽  
Monica Nardi ◽  
Maria Luisa Di Gioia ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Liquid Iron ◽  
Catalytic System ◽  
Dipolar Cycloaddition ◽  
Homogeneous Catalyst ◽  
Mechanistic Studies ◽  
Elimination Process ◽  
Cheap Method

An efficient, eco-compatible and very cheap method for the construction of triazoles via eliminative azide&ndash;olefin cycloaddition (EAOC) reaction has been developed by a catalytic system IL/FeCl3, offering an highly regioselective approach to structurally diverse 1,5-disubstituted 1,2,3-triazoles in up to 95% yield. This strategy features the reuse of catalytic system through simple operations. Mechanistic studies indicated that an asynchronous concerted dipolar cycloaddition-elimination process might be involved.

scholarly journals First experimental evidence for a bis-ethene chromium(I) complex forming from an activated ethene oligomerization catalyst

2020 ◽  
Vol 6 (51) ◽  
pp. eabd7057
Author(s):  
S. Chabbra ◽  
D. M. Smith ◽  
N. L. Bell ◽  
A. J. B. Watson ◽  
M. Bühl ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Experimental Evidence ◽  
Catalytic System ◽  
Isotope Labeling ◽  
Catalytic Transformation ◽  
Mechanistic Studies ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

A bis-ethene chromium(I) species, which is the postulated key intermediate in the widely accepted metallacyclic mechanism for ethene oligomerization, is experimentally observed. This catalytic transformation is an important commercial route to linear α-olefins (primarily, 1-hexene and 1-octene), which act as comonomers for the production of polyethene. Here, electron paramagnetic resonance studies of a catalytic system based on [Cr(CO)4(PNP)][Al(OC(CF3)3)4] [PNP = Ph2PN(iPr)PPh2] activated with Et6Al2 provide the first unequivocal evidence for a chromium(I) bis-ethene complex. The concentration of this species is enhanced under ethene and isotope labeling studies that confirm its composition as containing [Cr(C2H4)2(CO)2(PNP)]+. These observations open a new route to mechanistic studies of selective ethene oligomerization.

Mechanistic Study and Development of Catalytic Reactions of Sm(II)

2018 ◽  
Author(s):  
Sandepan Maity ◽  
Robert Flowers
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Proton Donor ◽  
Catalytic Reactions ◽  
Mechanistic Study ◽  
Mechanistic Studies ◽  
Cyclization Reactions ◽  
Mechanistic Approach ◽  
Donor Source

Despite the broad utility and application of SmI<sub>2</sub>in synthesis, the reagent is used in stoichiometric amounts and has a high molecular weight, resulting in a large amount of material being used for reactions requiring one or more equivalents of electrons. We report mechanistic studies on catalytic reactions of Sm(II) employing a terminal magnesium reductant and trimethyl silyl chloride in concert with a non-coordinating proton donor source. Reactions using this approach permitted reductions with as little as 1 mol% Sm. The mechanistic approach enabled catalysis employing HMPA as a ligand, facilitating the development of catalytic Sm(II) 5-<i>exo</i>-<i>trig </i>ketyl olefin cyclization reactions.

scholarly journals Development of highly efficient platinum catalysts for hydroalkoxylation and hydroamination of unactivated alkenes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yali Zhou ◽  
Xingjun Xu ◽  
Hongwei Sun ◽  
Guanyu Tao ◽  
Xiao-Yong Chang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Rational Design ◽  
Platinum Catalysts ◽  
High Reactivity ◽  
Structural Components ◽  
Mechanistic Studies ◽  
Mild Conditions ◽  
Naturally Occurring ◽  
Donor Acceptor ◽  
Type Intermediate

AbstractHydrofunctionalization, the direct addition of an X–H (e.g., X=O, N) bond across an alkene, is a desirable strategy to make heterocycles that are important structural components of naturally occurring molecules. Described here is the design and discovery of “donor–acceptor”-type platinum catalysts that are highly effective in both hydroalkoxylation and hydroamination of unactivated alkenes over a broad range of substrates under mild conditions. A number of alkene substitution patterns are accommodated, including tri-substituted, 1,1-disubstituted, (E)-disubstituted, (Z)-disubstituted and even mono-substituted double bonds. Detailed mechanistic investigations suggest a plausible pathway that includes an unexpected dissociation/re-association of the electron-deficient ligand to form an alkene-bound “donor–acceptor”-type intermediate. These mechanistic studies help understand the origins of the high reactivity exhibited by the catalytic system, and provide a foundation for the rational design of chiral catalysts towards asymmetric hydrofunctionalization reactions.

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