scholarly journals Enantioselective Construction of Trialkyl Tertiary Centers via Ni-Catalyzed Markovnikov Hydrocarbofunctionalizations of Unactivated Olefins and Electrophiles

2021 ◽  
Author(s):  
Wei Shu ◽  
Peng-Fei Yang ◽  
Jian-Xin Liang ◽  
Han-Tong Zhao ◽  
Jian-Xin Zhang ◽  
...  
Keyword(s):  
Room Temperature ◽  
Functional Group ◽  
Carbon Centers ◽  
Alkyl Electrophiles ◽  
Efficient Construction ◽  
Chiral Centers

Routes to efficient construction of fully aliphatic substituted tertiary chiral centers are highly challenging and desirable. Herein, a Ni-catalyzed enantioselective hydroalkylation of unactivated alkenes at room temperature is described, providing a general and practical access to tertiary stereogenic carbon centers with three alkyl substituents. This reaction involves the regio- and stereoselective hydrometalation of unactivated alkenes with Markovnikov selectivity, followed by coupling with unactivated alkyl electrophiles to access tertiary chiral centers with full alkyl substituents. The mild and robust conditions enable the use of terminal and internal unactivated alkenes as well as primary and secondary unactivated alkyl, benzyl, propargyl halides for the construction of diverse trialkyl tertiary stereogenic carbon centers with broad functional group tolerance.<br>

scholarly journals Enantioselective Construction of Trialkyl Tertiary Centers via Ni-Catalyzed Markovnikov Hydrocarbofunctionalizations of Unactivated Olefins and Electrophiles

2021 ◽  
Author(s):  
Wei Shu ◽  
Peng-Fei Yang ◽  
Jian-Xin Liang ◽  
Han-Tong Zhao ◽  
Jian-Xin Zhang ◽  
...  
Keyword(s):  
Room Temperature ◽  
Functional Group ◽  
Carbon Centers ◽  
Alkyl Electrophiles ◽  
Efficient Construction ◽  
Chiral Centers

Routes to efficient construction of fully aliphatic substituted tertiary chiral centers are highly challenging and desirable. Herein, a Ni-catalyzed enantioselective hydroalkylation of unactivated alkenes at room temperature is described, providing a general and practical access to tertiary stereogenic carbon centers with three alkyl substituents. This reaction involves the regio- and stereoselective hydrometalation of unactivated alkenes with Markovnikov selectivity, followed by coupling with unactivated alkyl electrophiles to access tertiary chiral centers with full alkyl substituents. The mild and robust conditions enable the use of terminal and internal unactivated alkenes as well as primary and secondary unactivated alkyl, benzyl, propargyl halides for the construction of diverse trialkyl tertiary stereogenic carbon centers with broad functional group tolerance.<br>

Enantioselective C(sp3)–C(sp3) Cross-Coupling of Non-activated Alkyl Electrophiles via Nickel Hydride Catalysis

2020 ◽  
Author(s):  
Srikrishna Bera ◽  
Runze Mao ◽  
Xile Hu
Keyword(s):  
Organic Molecules ◽  
Functional Group ◽  
Cross Coupling ◽  
Building Blocks ◽  
Carbon Centers ◽  
Mild Conditions ◽  
Drug Molecules ◽  
Nickel Hydride ◽  
Alkyl Electrophiles ◽  
Attractive Candidate

Cross-coupling of two alkyl fragments is an efficient method to produce organic molecules rich in sp<sup>3</sup>-hydridized carbon centers, which are attractive candidate compounds in drug discovery. Enantioselective C(sp<sup>3</sup>)-C(sp<sup>3</sup>) coupling, especially of alkyl electrophiles without an activating group (aryl, vinyl, carbonyl) is challenging. Here we report a strategy based on nickel hydride addition to internal olefins followed by nickel-catalyzed alkyl-alkyl coupling. This strategy enables enantioselective cross-coupling of non-activated alkyl iodides with alkenyl boronates to produce chiral alkyl boronates. Employing readily available and stable olefins as pro-chiral nucleophiles, the coupling proceeds under mild conditions and exhibits broad scope and high functional group tolerance. Applications in late-stage functionalization of natural products and drug molecules, synthesis of chiral building blocks, and enantioselective formal synthesis of (<i>S</i>)-(+)-Pregabalin are demonstrated.<br>

Enantioselective C(sp3)–C(sp3) Cross-Coupling of Non-activated Alkyl Electrophiles via Nickel Hydride Catalysis

2020 ◽  
Author(s):  
Srikrishna Bera ◽  
Runze Mao ◽  
Xile Hu
Keyword(s):  
Organic Molecules ◽  
Functional Group ◽  
Cross Coupling ◽  
Building Blocks ◽  
Carbon Centers ◽  
Mild Conditions ◽  
Drug Molecules ◽  
Nickel Hydride ◽  
Alkyl Electrophiles ◽  
Attractive Candidate

Cross-coupling of two alkyl fragments is an efficient method to produce organic molecules rich in sp<sup>3</sup>-hydridized carbon centers, which are attractive candidate compounds in drug discovery. Enantioselective C(sp<sup>3</sup>)-C(sp<sup>3</sup>) coupling, especially of alkyl electrophiles without an activating group (aryl, vinyl, carbonyl) is challenging. Here we report a strategy based on nickel hydride addition to internal olefins followed by nickel-catalyzed alkyl-alkyl coupling. This strategy enables enantioselective cross-coupling of non-activated alkyl iodides with alkenyl boronates to produce chiral alkyl boronates. Employing readily available and stable olefins as pro-chiral nucleophiles, the coupling proceeds under mild conditions and exhibits broad scope and high functional group tolerance. Applications in late-stage functionalization of natural products and drug molecules, synthesis of chiral building blocks, and enantioselective formal synthesis of (<i>S</i>)-(+)-Pregabalin are demonstrated.<br>

Conformation and electronic structure of aromatic chloroformates

1987 ◽  
Vol 52 (4) ◽  
pp. 970-979 ◽  
Author(s):  
Otto Exner ◽  
Pavel Fiedler
Keyword(s):  
Electronic Structure ◽  
Oxygen Atom ◽  
Strong Interaction ◽  
Electron Distribution ◽  
Room Temperature ◽  
Functional Group ◽  
Dipole Moments ◽  
Carbonyl Oxygen ◽  
Nonpolar Solvents ◽  
Single Method

Aromatic chloroformates Ib-Ie were shown to exist in the ap conformation, in agreement with aliphatic chloroformates, i.e. the alkyl group is situated cis to the carbonyl oxygen atom as it is the case in all esters. While 4-nitrophenyl chloroformate (Ie) is in this conformation in crystal, in solution at most several tenths of percent of the sp conformation may be populated at room temperature and in nonpolar solvents only. A new analysis of dipole moments explained the previous puzzling results and demonstrated the impossibility to determine the conformation by this single method, in consequence of the strong interaction of adjoining bonds. If, however, the ap conformation is once proven, the dipole moments reveal some features of the electron distribution on the functional group, characterized by the enhanced polarity of the C-Cl bond and reduced polarity of the C=O bond. This is in agreement with the observed bond lengths and angles.

Rh(III)-Catalyzed Olefination and Alkylation of Arenes with Maleimides: A Tunable Strategy for C(sp2)–H Functionalization

Synthesis ◽  
2021 ◽  
Author(s):  
Hongji Li ◽  
Wenjie Zhang ◽  
Xueyan Liu ◽  
Zhenfeng Tian
Keyword(s):  
Room Temperature ◽  
Functional Group ◽  
Reaction Conditions ◽  
Bond Functionalization ◽  
Alkylation Process ◽  
Coupling Partner

AbstractWe herein report a new nitrogen-directed Rh(III)-catalyzed C(sp2)–H bond functionalization of N-nitrosoanilines and azoxybenzenes with maleimides as a coupling partner, in which the olefination/alkylation process can be finely controlled at room temperature by variation of the reaction conditions. This method shows excellent functional group tolerance, and presents a mild access to the resulting olefination/alkylation products in moderate to good yields.

An efficient construction of CN bond under catalyst‐free and room temperature conditions

2021 ◽  
Vol 58 (5) ◽  
pp. 1179-1191
Author(s):  
Jinpeng Zhang ◽  
Jing Liu ◽  
Lei Dai ◽  
Yuqian Ge ◽  
Linlin Xu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Catalyst Free ◽  
Temperature Conditions ◽  
Efficient Construction

Diiiodine/Potassium Persulfate Mediated Synthesis of 1,2,3-Thiadiazoles from N-Tosylhydrazones and a Thiocyanate Salt as a Sulfur Source under Transition-Metal-Free Conditions

Synlett ◽  
2021 ◽  
Author(s):  
Yadong Sun ◽  
Ablimit Abdukader ◽  
Yuhan Lu ◽  
Chenjiang Liu
Keyword(s):  
Transition Metal ◽  
Efficient Method ◽  
Room Temperature ◽  
Functional Group ◽  
Ammonium Thiocyanate ◽  
Potassium Persulfate ◽  
Sulfur Source ◽  
Coupling Reactions ◽  
Wide Scope ◽  
Metal Free

AbstractA highly efficient method for the synthesis of 1,2,3-thiadiazoles has been developed by utilizing readily available tosylhydrazones and ammonium thiocyanate with ecofriendly EtOH as the solvent at room temperature. The reaction shows a wide scope of substrates and good functional-group tolerance. This protocol can be scaled up to a gram level and can be applied to coupling reactions with 4-(4-bromophenyl)-1,2,3-thiadiazole as the substrate.

Functional Group Manipulations

2008 ◽  
Author(s):  
Jie Jack Li ◽  
Chris Limberakis ◽  
Derek A. Pflum
Keyword(s):  
Column Chromatography ◽  
Room Temperature ◽  
Functional Group ◽  
Lithium Bromide ◽  
Methyl Methanesulfonate ◽  
Organic Layer ◽  
Reduced Pressure ◽  
Organic Extracts ◽  
Aqueous Layer ◽  
G 34

CBr4–Ph3P is very straightforward and widely used. Workup and purification can be messy at times because of the by-product, Ph3PO. To a mixture of the alcohol (0.800 g, 3.36 mmol) and carbon tetrabromide (1.337 g, 4.03 mmol) in CH2Cl2 at 0 ºC was added a solution of PPh3 (1.319 g, 5.03 mmol) in CH2Cl2 (3 mL). The reaction mixture was stirred at room temperature for 1 h, concentrated under reduced pressure, and purified by column chromatography to afford the bromide (0.941 g, 93% yield). Reference: Hu, T.-S.; Yu, Q.; Wu, Y.-L.; Wu, Y. J. Org. Chem. 2001, 66, 853–861. A two-step sequence consisting of mesylate formation followed by treatment with LiBr can also be used. This procedure involves two steps, but workup and purification are very straightforward. The bromide can be carried out to the next step without further purification in many cases. To a solution of 5-hydroxymethyl-1-methylcyclopentene (3.8 g, 34 mmol) in CH2 Cl2 (50 mL) at 0 ºC was added triethylamine (5.2 mL, 37 mmol) followed by methanesulfonyl chloride (2.9 mL, 37 mmol). The mixture was stirred at 0 ºC for 5 h and then water was added. The organic layer was separated and the aqueous layer was extracted with ether. The combined organic extracts were dried over MgSO4 and the solvent was removed under reduced pressure to give 6.4 g (98%) of (2-methylcyclopent-2- enyl)methyl methanesulfonate, which was used in the next step without further purification. A solution containing the mesylate (6.4 g, 34 mmol) in acetone (70 mL) was treated with lithium bromide (8.89 g, 102 mmol). The mixture was heated at reflux for 6 h, cooled to room temperature, diluted with water, extracted with ether, and the combined ethereal extracts were dried over MgSO4. Removal of the solvent under reduced pressure gave 4.6 g (78%) of 5-bromomethyl-1-methylcyclopentene, which was used in the next step without further purification.

scholarly journals Effect of Functionalized Carbon Nanotubes in the Detection of Benzene at Room Temperature

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Nurjahirah Janudin ◽  
Norli Abdullah ◽  
Wan Md Zin Wan Yunus ◽  
Faizah Md Yasin ◽  
Mohd Hanif Yaacob ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Acid Treatment ◽  
Room Temperature ◽  
Functional Group ◽  
Group Performance ◽  
Active Area ◽  
Functionalized Carbon Nanotubes ◽  
Sensing Material

In this paper, carbon nanotubes (CNTs) were functionalized by acid treatment and further functionalized with dodecylamine and were designated as CNT-carboxylic and CNT-amide, respectively. Then, functionalized CNTs produced were characterized with various methods to verify the attachment of a functional group. Performance of the functionalized CNTs in the detection of benzene gas was monitored at room temperature. The sample was dropped cast on the interdigitated transducer (IDT), and the changes in resistivity were recorded by a digital multimeter in a customized chamber under controlled humidity (∼55%) environment. Based on the findings, it showed that the functionalized CNTs provide an extra active area for interaction between the gas analyte and CNTs, thus increasing their response and improving the sensitivity of the sensing material.

Sign in / Sign up

Export Citation Format

Share Document