scholarly journals Transition-Metal-Free Boryl Substitution Using Silylboranes and Alkoxy Bases

Synlett ◽  
2017 ◽  
Vol 28 (11) ◽  
pp. 1258-1267 ◽  
Author(s):  
Hajime Ito ◽  
Eiji Yamamoto ◽  
Satoshi Maeda ◽  
Tetsuya Taketsugu
Keyword(s):  
Transition Metal ◽  
Functional Group ◽  
Experimental Studies ◽  
Transition Metal Catalysts ◽  
Alkyl Halides ◽  
Aryl Halides ◽  
Nucleophilic Attack ◽  
Important Class ◽  
Mechanistic Studies ◽  
Induced Reaction

Silylboranes are used as borylation reagents for organohalides in the presence of alkoxy bases without transition-metal catalysts. PhMe2Si–B(pin) reacts with a variety of aryl, alkenyl, and alkyl halides, including sterically hindered examples, to provide the corresponding organoboronates in good yields with high borylation/silylation ratios, showing good functional group compatibility. Halogenophilic attack of a silyl nucleophile on organohalides, and subsequent nucleophilic attack on the boron electrophile are identified to be crucial, based on the results of extensive theoretical and experimental studies. This boryl­ation reaction is further applied to the first direct dimesitylboryl (BMes2) substitution of aryl halides using Ph2MeSi–BMes2 and Na(O-t-Bu), affording aryldimesitylboranes, which are regarded as an important class of compounds for organic materials.1 Introduction2 Boryl Substitution of Organohalides with PhMe2Si–B(pin)/Alkoxy Bases3 Mechanistic Investigations4 DFT Mechanistic Studies Using an Artificial Force Induced Reaction (AFIR) Method5 Dimesitylboryl Substitution of Aryl Halides with Ph2MeSi–BMes2/Na(O-t-Bu)6 Conclusion

scholarly journals Pd-catalyzed intramolecular addition of active methylene compounds to alkynes with subsequent cross-coupling with (hetero)aryl halides

RSC Advances ◽  
2019 ◽  
Vol 9 (68) ◽  
pp. 40152-40167 ◽  
Author(s):  
Aleksandra Błocka ◽  
Paweł Woźnicki ◽  
Marek Stankevič ◽  
Wojciech Chaładaj
Keyword(s):  
Functional Group ◽  
Cross Coupling ◽  
Aryl Halides ◽  
Mechanistic Studies ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Active Methylene Compounds ◽  
Tandem Cyclization ◽  
Rate Limiting ◽  
Active Methylene

A tandem cyclization/coupling of acetylenic active methylene compounds with aryl halides features broad scope and excellent functional group compatibility. Mechanistic studies identified 5-exo-dig cyclization as the rate limiting step.

scholarly journals Weinreb Amides as Directing Groups for Transition Metal-Catalyzed C-H Functionalizations

Molecules ◽  
2019 ◽  
Vol 24 (5) ◽  
pp. 830 ◽  
Author(s):  
Jagadeesh Kalepu ◽  
Lukasz Pilarski
Keyword(s):  
Transition Metal ◽  
Functional Group ◽  
Metal Catalysts ◽  
Mechanistic Studies ◽  
Weinreb Amides ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

Weinreb amides are a privileged, multi-functional group with well-established utility in classical synthesis. Recently, several studies have demonstrated the use of Weinreb amides as interesting substrates in transition metal-catalyzed C-H functionalization reactions. Herein, we review this part of the literature, including the metal catalysts, transformations explored so far and specific insights from mechanistic studies.

Oxymetalation or Oxidative Cyclization? Mechanism of Pd-Catalyzed Annulation of Enynones

2021 ◽  
Author(s):  
Hao Ni ◽  
xiaoqian he ◽  
Kongbao Zhong ◽  
Haohua Chen ◽  
Wei Lai ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Catalysts ◽  
Oxidative Cyclization ◽  
Transition Metal Catalysts ◽  
Nucleophilic Attack ◽  
Furan Derivatives ◽  
Coinage Metals

Enynones are powerful synthons for constructing furan derivatives in the presence of transition metal catalysts. Unlike the conventional intramolecular nucleophilic attack with the activation of coinage metals, we propose that...

Recent Advances in the Sustainable Synthesis of Quinazolines Using Earth-Abundant First Row Transition Metals

2020 ◽  
Vol 24 (15) ◽  
pp. 1775-1792 ◽  
Author(s):  
Sumera Zaib ◽  
Imtiaz Khan
Keyword(s):  
Transition Metals ◽  
Organic Synthesis ◽  
Molecular Diversity ◽  
Functional Group ◽  
Transition Metal Catalysts ◽  
Mechanistic Studies ◽  
Pharmacological Activities ◽  
Modular Assembly ◽  
Diverse Range ◽  
Earth Abundant

Achieving challenging molecular diversity in contemporary chemical synthesis remains a formidable hurdle, particularly in the delivery of diversified bioactive heterocyclic pharmacophores for drug design and pharmaceutical applications. The coupling methods that combine a diverse range of readily accessible and commercially available pools of substrates under the action of earth-abundant first row transition metal catalysts have certainly matured into powerful tools, thus offering sustainable alternatives to revolutionize the organic synthesis. This minireview highlights the successful utilization of the catalytic ability of the first row transition metals (Mn, Fe, Ni, Cu) in the modular assembly of quinazoline heterocycle, ubiquitously present in numerous alkaloids, commercial medicines and is associated with a diverse range of pharmacological activities. The broad substrate scope and high functional group tolerance of the targeted methods were extensively explored, identifying the future strategic advances in the field. The investigation will also be exemplified with mechanistic studies as long as they are deemed necessary.

scholarly journals One-pot synthesis of propynoates and propynenitriles

2017 ◽  
Vol 95 (2) ◽  
pp. 144-148 ◽  
Author(s):  
Fan Shu ◽  
Qingjuan Zheng ◽  
Wanrong Dong ◽  
Zhihong Peng ◽  
Delie An
Keyword(s):  
Low Temperature ◽  
Transition Metal ◽  
Functional Group ◽  
High Efficiency ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
One Pot ◽  
Efficient Transformation ◽  
One Pot Synthesis ◽  
Substituted Acetylenes

An efficient transformation towards propynoates and propynenitriles is herein described. The practical methodology was conducted at low temperature (–78 or –60 °C) in a one-pot manner with the assistance of base rather than any transition metal catalysts. The base-induced protocol exhibits good functional group tolerance (up to 28 examples) and high efficiency (up to 92% yields) towards substituted acetylenes of great synthetic significance, which was also well demonstrated by the gram-scale reactions.

scholarly journals Nickel-catalyzed electrochemical carboxylation of unactivated aryl and alkyl halides with CO2

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Guo-Quan Sun ◽  
Wei Zhang ◽  
Li-Li Liao ◽  
Li Li ◽  
Zi-Hao Nie ◽  
...  
Keyword(s):  
Catalytic System ◽  
Functional Group ◽  
Alkyl Halides ◽  
Aryl Halides ◽  
Aryl Chlorides ◽  
Mild Conditions ◽  
Aryl Bromides ◽  
Alkyl Bromides ◽  
Pseudo Halides ◽  
Electrochemical Carboxylation

AbstractElectrochemical catalytic reductive cross couplings are powerful and sustainable methods to construct C−C bonds by using electron as the clean reductant. However, activated substrates are used in most cases. Herein, we report a general and practical electro-reductive Ni-catalytic system, realizing the electrocatalytic carboxylation of unactivated aryl chlorides and alkyl bromides with CO2. A variety of unactivated aryl bromides, iodides and sulfonates can also undergo such a reaction smoothly. Notably, we also realize the catalytic electrochemical carboxylation of aryl (pseudo)halides with CO2 avoiding the use of sacrificial electrodes. Moreover, this sustainable and economic strategy with electron as the clean reductant features mild conditions, inexpensive catalyst, safe and cheap electrodes, good functional group tolerance and broad substrate scope. Mechanistic investigations indicate that the reaction might proceed via oxidative addition of aryl halides to Ni(0) complex, the reduction of aryl-Ni(II) adduct to the Ni(I) species and following carboxylation with CO2.

scholarly journals Focusing on the Catalysts of the Pd- and Ni-Catalyzed Hirao Reactions

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3897
Author(s):  
György Keglevich ◽  
Réka Henyecz ◽  
Zoltán Mucsi
Keyword(s):  
Experimental Data ◽  
Transition Metal ◽  
Ligand Exchange ◽  
Theoretical Calculations ◽  
Reductive Elimination ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Aryl Halides ◽  
Feature Article ◽  
Bond Forming

The Hirao reaction involving the phosphinoylation or phosphonation of aryl halides by >P(O)H reagents is a P–C bond forming transformation belonging to the recently very hot topic of cross-couplings. The Pd- or Ni-catalyzed variations take place via the usual cycle including oxidative addition, ligand exchange, and reductive elimination. However, according to the literature, the nature of the transition metal catalysts is not unambiguous. In this feature article, the catalysts described for the Pd(OAc)2-promoted cases are summarized, and it is concluded that the “(HOY2P)2Pd(0)” species (Y = aryl, alkoxy) is the real catalyst. In our model, the excess of the >P(O)H reagent served as the P-ligand. During the less studied Ni(II)-catalyzed instances the “(HOY2P)(−OY2P)Ni(II)Cl−” form was found to enter the catalytic cycle. The newest conclusions involving the exact structure of the catalysts, and the mechanism for their formation explored by us were supported by our earlier experimental data and theoretical calculations.

scholarly journals Direct alkylation of N,N-dialkyl benzamides with methyl sulfides under transition metal-free conditions

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Can-Can Bao ◽  
Hui-Zhen Du ◽  
Yan-Long Luo ◽  
Bing-Tao Guan
Keyword(s):  
Transition Metal ◽  
Functional Group ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Amide Bond ◽  
Selective Synthesis ◽  
Lithium Diisopropylamide ◽  
Organometallic Reagents ◽  
Metal Free ◽  
Resonance Stabilization

AbstractAmides are a fundamental and widespread functional group, and are usually considered as poor electrophiles owing to resonance stabilization of the amide bond. Various approaches have been developed to address challenges in amide transformations. Nonetheless, most methods use activated amides, organometallic reagents or transition metal catalysts. Here, we report the direct alkylation of N,N-dialkyl benzamides with methyl sulfides promoted by the readily available base LDA (lithium diisopropylamide). This approach successfully achieves an efficient and selective synthesis of α-sulfenylated ketones without using transition-metal catalysts or organometallic reagents. Preliminary mechanism studies reveal that the deprotonative aroylation of methyl sulfides is promoted by the directed ortho-lithiation of the tertiary benzamide with LDA.

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