Regio- and Stereoselective (SN2) N-, O-, C- and S-Alkylation using Trialkyl Phosphates

Synthesis ◽  
2021 ◽  
Author(s):  
Amit banerjee ◽  
Tomohiro Hattori ◽  
Hisashi Yamamoto
Keyword(s):  
Room Temperature ◽  
Alkylating Agents ◽  
Alkyl Halides ◽  
Back Side ◽  
Alkyl Groups ◽  
Wide Range ◽  
Leaving Group ◽  
Reaction Proceeds ◽  
Trialkyl Phosphates ◽  
Trialkyl Phosphate

Bimolecular nucleophilic substitution (S N 2) is one of the most known fundamental reactions in organic chemistry to generate new molecules from two molecules. In principle, a nucleophile attacks from the back side of an alkylating agent having a suitable leaving group, most commonly using a halide. However, alkyl halides are expensive, very harmful, toxic and not so stable which makes them problematic for laboratory use. In contrast, trialkyl phosphates are cheap, readily accessible, stable at room temperature, under air, and are easy to handle but rarely used as alkylating agents in organic synthesis. Here, we describe a mild, straightforward and powerful method for nucleophilic alkylation of various nucleophiles such as N-, O-, C- and S- using readily available trialkyl phosphate. The reaction proceeds smoothly with excellent yield and quantitative yield in many cases and covers a wide range of substrates. Further, the rare stereoselective transfer of secondary alkyl groups has been achieved with inversion of configuration of chiral centers (up to >99% ee).

Alkene Difunctionalization Directed by Free Amines: Diamine Synthesis via Nickel-Catalyzed 1,2-Carboamination

2021 ◽  
Author(s):  
Taeho Kang ◽  
José Manuel González ◽  
Zi-Qi Li ◽  
Klement Foo ◽  
Peter Cheng ◽  
...  
Keyword(s):  
Nickel Catalyst ◽  
Room Temperature ◽  
Kinetic Studies ◽  
Fine Tuning ◽  
Secondary Amines ◽  
Protecting Group ◽  
Wide Range ◽  
Leaving Group ◽  
Primary And Secondary Amines ◽  
Reaction Proceeds

A versatile method to access differentially substituted 1,3- and 1,4-diamines via a nickel-catalyzed three-component 1,2-carboamination of alkenyl amines with aryl/alkenylboronic ester nucleophiles and N–O electrophiles is reported. The reaction proceeds efficiently with free primary and secondary amines without needing a directing auxiliary or protecting group, and is enabled by fine-tuning the leaving group on the N–O reagent. The transformation is highly regioselective and compatible with a wide range of coupling partners and alkenyl amine substrates, all performed at room temperature. A series of kinetic studies support a mechanism in which alkene coordination to the nickel catalyst is turnover-limiting.

Aliphatic Radical Relay Heck Reaction at Unactivated C(sp3)–H Sites of Alcohols

2018 ◽  
Author(s):  
Padon Chuentragool ◽  
Dongari Yadagiri ◽  
Taiki Morita ◽  
Sumon Sarkar ◽  
Marvin Parasram ◽  
...  
Keyword(s):  
Visible Light ◽  
Heck Reaction ◽  
Room Temperature ◽  
Halogen Atom ◽  
Organic Molecules ◽  
Alkyl Halides ◽  
Aliphatic Alcohols ◽  
Aliphatic Radical ◽  
Reaction Proceeds

<div>The Mizoroki−Heck reaction is one of the most efficient methods for alkenylation of</div><div>aryl, vinyl, and alkyl halides. Due to its innate nature, this protocol requires the employment of compounds possessing a halogen atom at the site of functionalization. However, the accessibility of organic molecules possessing a halogen atom at a particular site in aliphatic systems is extremely limited. Thus, a protocol that would allow a Heck reaction to occur at a specific non-functionalized C(sp3)−H site would be highly desirable.</div><div>Here, we report a radical relay Heck reaction which allows for a selective remote</div>alkenylation of aliphatic alcohols at unactivated β-, γ- and δ-C(sp3 20 )–H sites. The use of easily installable/removable Si-based auxiliary enables selective I-atom/radical translocation events at remote C−H sites followed by the Heck reaction. Notably, the reaction proceeds smoothly under mild visible light-mediated conditions at room temperature, producing highly modifiable and valuable alkenol products from readily available alcohols feedstocks. <br>

scholarly journals Direct C(sp2)–H alkylation of unactivated arenes enabled by photoinduced Pd catalysis

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Daeun Kim ◽  
Geun Seok Lee ◽  
Dongwook Kim ◽  
Soon Hyeok Hong
Keyword(s):  
Functional Group ◽  
Alkyl Halide ◽  
Alkyl Halides ◽  
Biologically Active ◽  
One Pot ◽  
Bond Forming ◽  
Alkyl Groups ◽  
Alkyl Bromides ◽  
Reaction Proceeds ◽  
Alkylation Reactions

AbstractDespite the fundamental importance of efficient and selective synthesis of widely useful alkylarenes, the direct catalytic C(sp2)–H alkylation of unactivated arenes with a readily available alkyl halide remains elusive. Here, we report the catalytic C(sp2)–H alkylation reactions of unactivated arenes with alkyl bromides via visible-light induced Pd catalysis. The reaction proceeds smoothly under mild conditions without any skeletal rearrangement of the alkyl groups. The direct syntheses of structurally diverse linear and branched alkylarenes, including the late-stage phenylation of biologically active molecules and an orthogonal one-pot sequential Pd-catalyzed C–C bond-forming reaction, are achieved with exclusive chemoselectivity and exceptional functional group tolerance. Comprehensive mechanistic investigations through a combination of experimental and computational methods reveal a distinguishable Pd(0)/Pd(I) redox catalytic cycle and the origin of the counter-intuitive reactivity differences among alkyl halides.

Aliphatic Radical Relay Heck Reaction at Unactivated C(sp3)–H Sites of Alcohols

2018 ◽  
Author(s):  
Padon Chuentragool ◽  
Dongari Yadagiri ◽  
Taiki Morita ◽  
Sumon Sarkar ◽  
Marvin Parasram ◽  
...  
Keyword(s):  
Visible Light ◽  
Heck Reaction ◽  
Room Temperature ◽  
Halogen Atom ◽  
Organic Molecules ◽  
Alkyl Halides ◽  
Aliphatic Alcohols ◽  
Aliphatic Radical ◽  
Reaction Proceeds

<div>The Mizoroki−Heck reaction is one of the most efficient methods for alkenylation of</div><div>aryl, vinyl, and alkyl halides. Due to its innate nature, this protocol requires the employment of compounds possessing a halogen atom at the site of functionalization. However, the accessibility of organic molecules possessing a halogen atom at a particular site in aliphatic systems is extremely limited. Thus, a protocol that would allow a Heck reaction to occur at a specific non-functionalized C(sp3)−H site would be highly desirable.</div><div>Here, we report a radical relay Heck reaction which allows for a selective remote</div>alkenylation of aliphatic alcohols at unactivated β-, γ- and δ-C(sp3 20 )–H sites. The use of easily installable/removable Si-based auxiliary enables selective I-atom/radical translocation events at remote C−H sites followed by the Heck reaction. Notably, the reaction proceeds smoothly under mild visible light-mediated conditions at room temperature, producing highly modifiable and valuable alkenol products from readily available alcohols feedstocks. <br>

scholarly journals Cobalt-catalyzed directed alkylation of arenes with primary and secondary alkyl halides

2014 ◽  
Vol 86 (3) ◽  
pp. 419-424 ◽  
Author(s):  
Naohiko Yoshikai ◽  
Ke Gao
Keyword(s):  
Alkyl Radical ◽  
Room Temperature ◽  
Alkylating Agents ◽  
Alkyl Halide ◽  
Alkyl Halides ◽  
Single Electron Transfer ◽  
Directing Group ◽  
Aromatic Imines ◽  
Alkylation Reactions ◽  
Cobalt Species

Abstract A cobalt–N-heterocyclic carbene catalyst allows ortho-alkylation of aromatic imines with unactivated primary and secondary alkyl chlorides and bromides under room-temperature conditions. The scope of the reaction encompasses or complements that of cobalt-catalyzed ortho-alkylation reactions with olefins as alkylating agents that we developed previously. Stereochemical outcomes of secondary alkylation reactions suggest that the reaction involves single-electron transfer from a cobalt species to the alkyl halide to generate the corresponding alkyl radical. A cycloalkylated product obtained by this method can be transformed into unique spirocycles through manipulation of the directing group and the cycloalkyl groups.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

HREM observation of dislocations near room temperature fractures in silicon

1988 ◽  
Vol 46 ◽  
pp. 892-893
Author(s):  
M. H. Rhee ◽  
W. A. Coghlan
Keyword(s):  
Cross Section ◽  
Room Temperature ◽  
Single Crystal Silicon ◽  
Dislocation Nucleation ◽  
Back Side ◽  
Ion Milling ◽  
Crystal Silicon ◽  
Flat Surfaces ◽  
Induced Fractures ◽  
Vicker’S Microhardness

Silicon is believed to be an almost perfectly brittle material with cleavage occurring on {111} planes. In such a material at room temperature cleavage is expected to occur prior to any dislocation nucleation. This behavior suggests that cleavage fracture may be used to produce usable flat surfaces. Attempts to show this have failed. Such fractures produced in semiconductor silicon tend to occur on planes of variable orientation resulting in surfaces with a poor surface finish. In order to learn more about the mechanisms involved in fracture of silicon we began a HREM study of hardness indent induced fractures in thin samples of oxidized silicon.Samples of single crystal silicon were oxidized in air for 100 hours at 1000°C. Two pieces of this material were glued together and 500 μm thick cross-section samples were cut from the combined piece. The cross-section samples were indented using a Vicker's microhardness tester to produce cracks. The cracks in the samples were preserved by thinning from the back side using a combination of mechanical grinding and ion milling.

Evaluation of 99mTc-Label led Vitamin K4 as an Agent for Testicular Imaging

1991 ◽  
Vol 30 (01) ◽  
pp. 35-39 ◽  
Author(s):  
H. S. Durak ◽  
M. Kitapgi ◽  
B. E. Caner ◽  
R. Senekowitsch ◽  
M. T. Ercan
Keyword(s):  
Soft Tissue ◽  
Room Temperature ◽  
Normal Subjects ◽  
Left Testis ◽  
Wide Range ◽  
Activity Ratios ◽  
The Right ◽  
Radioactivity Levels

Vitamin K4 was labelled with 99mTc with an efficiency higher than 97%. The compound was stable up to 24 h at room temperature, and its biodistribution in NMRI mice indicated its in vivo stability. Blood radioactivity levels were high over a wide range. 10% of the injected activity remained in blood after 24 h. Excretion was mostly via kidneys. Only the liver and kidneys concentrated appreciable amounts of radioactivity. Testis/soft tissue ratios were 1.4 and 1.57 at 6 and 24 h, respectively. Testis/blood ratios were lower than 1. In vitro studies with mouse blood indicated that 33.9 ±9.6% of the radioactivity was associated with RBCs; it was washed out almost completely with saline. Protein binding was 28.7 ±6.3% as determined by TCA precipitation. Blood clearance of 99mTc-l<4 in normal subjects showed a slow decrease of radioactivity, reaching a plateau after 16 h at 20% of the injected activity. In scintigraphic images in men the testes could be well visualized. The right/left testis ratio was 1.08 ±0.13. Testis/soft tissue and testis/blood activity ratios were highest at 3 h. These ratios were higher than those obtained with pertechnetate at 20 min post injection.99mTc-l<4 appears to be a promising radiopharmaceutical for the scintigraphic visualization of testes.

General Cyclopropane Assembly via Enantioselective Redox-Active Carbene Transfer to Aliphatic Olefins

2018 ◽  
Author(s):  
Marc Montesinos-Magraner ◽  
Matteo Costantini ◽  
Rodrigo Ramirez-Contreras ◽  
Michael E. Muratore ◽  
Magnus J. Johansson ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Asymmetric Synthesis ◽  
Chemical Space ◽  
Synthetic Approach ◽  
Asymmetric Cyclopropanation ◽  
Redox Active ◽  
Wide Range ◽  
Leaving Group ◽  
Stereoelectronic Properties ◽  
Carbene Transfer

Asymmetric cyclopropane synthesis currently requires bespoke strategies, methods, substrates and reagents, even when targeting similar compounds. This limits the speed and chemical space available for discovery campaigns. Here we introduce a practical and versatile diazocompound, and we demonstrate its performance in the first unified asymmetric synthesis of functionalized cyclopropanes. We found that the redox-active leaving group in this reagent enhances the reactivity and selectivity of geminal carbene transfer. This effect enabled the asymmetric cyclopropanation of a wide range of olefins including unactivated aliphatic alkenes, enabling the 3-step total synthesis of (–)-dictyopterene A. This unified synthetic approach delivers high enantioselectivities that are independent of the stereoelectronic properties of the functional groups transferred. Our results demonstrate that orthogonally-differentiated diazocompounds are viable and advantageous equivalents of single-carbon chirons<i>.</i>

scholarly journals The Three-Component Synthesis of 4-Sulfonyl-1,2,3-triazoles via a Sequential Aerobic Copper-Catalyzed Sulfonylation and Dimroth Cyclization

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 581
Author(s):  
Max Van Hoof ◽  
Santhini Pulikkal Veettil ◽  
Wim Dehaen
Keyword(s):  
Room Temperature ◽  
Aromatic Ketones ◽  
Three Component Reaction ◽  
Reaction Proceeds

4-Sulfonyl-1,2,3-triazole scaffolds possess promising bioactivities and applications as anion binders. However, these structures remain relatively unexplored and efficient synthetic procedures for their synthesis remain desirable. A practical room-temperature, aerobic copper-catalyzed three-component reaction of aromatic ketones, sodium sulfinates, and azides is reported. This procedure allows for facile access to 4-sulfonyl-1,5-disubstituted-1,2,3-triazoles in yields ranging from 34 to 89%. The reaction proceeds via a sequential aerobic copper(II)chloride-catalyzed oxidative sulfonylation and the Dimroth azide–enolate cycloaddition.

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