General Route to Purin-2-ylmagnesium Halides by Metal–Halogen Exchange in Dichloromethane

Synlett ◽  
2020 ◽  
Vol 31 (05) ◽  
pp. 512-516
Author(s):  
Silvia Gazzola ◽  
Malcolm R. Gordon ◽  
Stephen D. Lindell
Keyword(s):  
Functional Group ◽  
Grignard Reagents ◽  
Ethylmagnesium Bromide ◽  
Ethereal Solution ◽  
Halogen Exchange ◽  
First Time

Treatment of a solution of a 9-alkyl- or 9-aryl-2-iodopurine in dichloromethane with an ethereal solution of ethylmagnesium bromide at –5 °C generates the corresponding purin-2-ylmagnesium bromide, which reacts with aldehydes to give the corresponding 2-(hydroxyalkyl)purines in yields of 53–84%. The purin-2-yl Grignard reagents show good functional-group tolerance to ester and nitro groups, and the method permits the synthesis of the previously unknown 6-unsubstituted 2-magnesiopurines for the first time. Performing the same procedure in THF as solvent resulted either in extensive decomposition or rapid isomerization to give purin-8-ylmagnesium halides.

An Improved Route to Purin-6-yl Magnesium Halides by Metal–Halogen Exchange in Dichloromethane

Synlett ◽  
2017 ◽  
Vol 29 (04) ◽  
pp. 473-476 ◽  
Author(s):  
Stephen Lindell ◽  
Malcolm Gordon ◽  
Daniel Richards
Keyword(s):  
Ambient Temperature ◽  
Ethylmagnesium Bromide ◽  
Ethereal Solution ◽  
Halogen Exchange

Treatment of a solution of 9-benzyl or 9-phenyl 6-iodopurine in dichloromethane with an ethereal solution of ethylmagnesium bromide at ambient temperature generates the corresponding purin-6-yl magnesium halides which react with aldehydes to give carbinols in 55–80% yield. Performing the same procedure with THF as solvent gave carbinols in much lower yields (≤15%).

Iridium-Catalyzed Silylation of C-H bonds in Unactivated Arenes: A Sterically-Encumbered Phenanthroline Ligand Accelerates Catalysis Enabling New Reactivity

2019 ◽  
Author(s):  
Caleb Karmel ◽  
Zhewei Chen ◽  
John Hartwig
Keyword(s):  
High Activity ◽  
Functional Group ◽  
Activity Analysis ◽  
High Reactivity ◽  
High Yield ◽  
Phen Ligand ◽  
Mechanistic Studies ◽  
Phenanthroline Ligand ◽  
First Time ◽  
New System

We report a new system for the silylation of aryl C-H bonds. The combination of [Ir(cod)(OMe)]<sub>2</sub> and 2,9-Me<sub>2</sub>-phenanthroline (2,9-Me<sub>2</sub>phen) catalyzes the silylation of arenes at lower temperatures and with faster rates than those reported previously, when the hydrogen byproduct is removed, and with high functional group tolerance and regioselectivity. Inhibition of reactions by the H<sub>2</sub> byproduct is shown to limit the silylation of aryl C-H bonds in the presence of the most active catalysts, thereby masking their high activity. Analysis of initial rates uncovered the high reactivity of the catalyst containing the sterically hindered 2,9-Me<sub>2</sub>phen ligand but accompanying rapid inhibition by hydrogen. With this catalyst, under a flow of nitrogen to remove hydrogen, electron-rich arenes, including those containing sensitive functional groups, undergo silylation in high yield for the first time, and arenes that underwent silylation with prior catalysts react over much shorter times with lower catalyst loadings. The synthetic value of this methodology is demonstrated by the preparation of key intermediates in the synthesis of medicinally important compounds in concise sequences comprising silylation and functionalization. Mechanistic studies demonstrate that the cleavage of the aryl C-H bond is reversible and that the higher rates observed with the 2,9-Me<sub>2</sub>phen ligand is due to a more thermodynamically favorable oxidative addition of aryl C-H bonds.

Sulfonyl Radical Triggered Selective Iodosulfonylation and Bicycli-zations of 1,6-Dienes

2021 ◽  
Author(s):  
Shi-Ping Wu ◽  
Dong-Kai Wang ◽  
Qing-Qing Kang ◽  
Guo-Ping Ge ◽  
Hongxing Zheng ◽  
...  
Keyword(s):  
Functional Group ◽  
High Selectivity ◽  
Reaction Conditions ◽  
First Time

A novel sulfonyl radical triggered selective iodosulfonylation and bicyclizations of 1,6-dienes has been described for the first time. High selectivity and efficiency, mild reaction conditions, excellent functional group compatibility, and...

The addition of organometallic reagents to tetramesityldigermene

2002 ◽  
Vol 80 (11) ◽  
pp. 1387-1392 ◽  
Author(s):  
Kyle L Fujdala ◽  
David W.K Gracey ◽  
Erica F Wong ◽  
Kim M Baines
Keyword(s):  
Ligand Exchange ◽  
Grignard Reagent ◽  
Thermal Conditions ◽  
Grignard Reagents ◽  
Ethylmagnesium Bromide ◽  
Organometallic Reagent ◽  
Organometallic Reagents ◽  
Thermal Cleavage

The thermolysis and photolysis of hexamesitylcyclotrigermane in the presence of ethylmagnesium bromide has been investigated. Under photochemical conditions, ethyldimesitylgermane, 1,2-diethyl-1,1,2-trimesityldigermane and ethyl-1,1,2,2-tetramesityldigermane were isolated and, under thermal conditions, 1,2,2-triethyl-1,1-dimesityl digermane and 2,2-diethyl-1,1,1-trimesityldigermane were isolated. The photolysis of hexamesitylcyclotrigermane in the presence of methyllithium has also been investigated. In both cases, the organometallic reagent adds to tetramesityl digermene and dimesitylgermylene formed by photochemical or thermal cleavage of the cyclotrigermane. In the case of the addition of the Grignard reagent, the resulting germyl Grignard reagent undergoes a facile ligand exchange reaction.Key words: digermene, germylene, Grignard reagents, alkyllithium reagents, germylmagnesium compounds, germyllithium compounds.

scholarly journals Iron-Catalyzed C(sp2)–C(sp3) Cross-Coupling of Aryl Chlorobenzoates with Alkyl Grignard Reagents

Molecules ◽  
2020 ◽  
Vol 25 (1) ◽  
pp. 230 ◽  
Author(s):  
Elwira Bisz ◽  
Michal Szostak
Keyword(s):  
Organic Synthesis ◽  
Nucleophilic Addition ◽  
Functional Group ◽  
High Selectivity ◽  
Cross Coupling ◽  
Environmentally Benign ◽  
Grignard Reagents ◽  
High Importance ◽  
Iron Salts ◽  
The Cross

Aryl benzoates are compounds of high importance in organic synthesis. Herein, we report the iron-catalyzed C(sp2)–C(sp3) Kumada cross-coupling of aryl chlorobenzoates with alkyl Grignard reagents. The method is characterized by the use of environmentally benign and sustainable iron salts for cross-coupling in the catalytic system, employing benign urea ligands in the place of reprotoxic NMP (NMP = N-methyl-2-pyrrolidone). It is notable that high selectivity for the cross-coupling is achieved in the presence of hydrolytically-labile and prone to nucleophilic addition phenolic ester C(acyl)–O bonds. The reaction provides access to alkyl-functionalized aryl benzoates. The examination of various O-coordinating ligands demonstrates the high activity of urea ligands in promoting the cross-coupling versus nucleophilic addition to the ester C(acyl)–O bond. The method showcases the functional group tolerance of iron-catalyzed Kumada cross-couplings.

A new synthesis of chloroheterocycles via metalhalogen exchange between trichloroacetyl derivatives and heteroaromatic lithium and Grignard reagents

1999 ◽  
Vol 588 (2) ◽  
pp. 155-159 ◽  
Author(s):  
Carla Boga ◽  
Erminia Del Vecchio ◽  
Luciano Forlani ◽  
Lilia Milanesi ◽  
Paolo Edgardo Todesco
Keyword(s):  
Grignard Reagents ◽  
New Synthesis ◽  
Halogen Exchange

Titanacyclopropanes as versatile intermediates for carbon-carbon bond formation in reactions with unsaturated compounds

2000 ◽  
Vol 72 (9) ◽  
pp. 1715-1719 ◽  
Author(s):  
O. G. Kulinkovich
Keyword(s):  
Reaction Mechanism ◽  
Bond Formation ◽  
Grignard Reagents ◽  
Allylic Alcohols ◽  
Ethylmagnesium Bromide ◽  
Carbon Bond ◽  
Unsaturated Compounds ◽  
Carbon Carbon Bond ◽  
Reaction Proceeds

Dialkoxytitanacyclopropane intermediates [or titanium (II)-olefin complexes] generated in situ from ethylmagnesium bromide and titanium (IV) isopropoxide react with allylic alcohols and allylic ethers to afford SN2' allylic ethylation products. The reaction proceeds with high regioselectivity and with low to high trans-/cis-stereoselectivity. This observation and others suggest a reaction mechanism involving an EtMgBr-initiated formation of titanacyclopentane ate complex 10 from titanacyclopropane-olefin complex 7 as a key step. Based on this assumption, a modified mechanism of titanium-mediated cyclopropanation of esters with Grignard reagents is proposed.

On the nature of the radical pairs involved in the Grignard reaction

1980 ◽  
Vol 58 (9) ◽  
pp. 932-937 ◽  
Author(s):  
Barend Johannes Schaart ◽  
Cornelis Blomberg ◽  
Otto Sjouke Akkerman ◽  
Friedrich Bickelhaupt
Keyword(s):  
Side Reactions ◽  
Grignard Reaction ◽  
Ethylmagnesium Bromide ◽  
Radical Pairs ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Alkyl Bromides ◽  
Halogen Exchange ◽  
Wurtz Coupling ◽  
Firm Evidence

During the simultaneous reaction of alkyl bromides and of p-halosubstituted benzyl bromides with magnesium in THF/C6D6 (1:4), CIDNP net effects (emission) are observed in the 1H nmr spectrum. The effects are opposite to those occurring during the reaction of preformed ethylmagnesium bromide and the benzyl bromides. These results constitute firm evidence that only alkyl radical pairs [Formula: see text] are responsible for the CIDNP effects, and that the radicals R• are generated in the Grignard reaction proper, rather than in unrelated side reactions such as Wurtz coupling or metal halogen exchange.

scholarly journals KO t Bu Promoted Selective Ring-Opening N-alkylation of 2-Oxazolines to Access 2-Aminoethyl Acetates and N-Substituted Thiazolidinones

2019 ◽  
Author(s):  
Qiao Lin ◽  
Shiling Zhang ◽  
Bin Li
Keyword(s):  
Ring Opening ◽  
Functional Group ◽  
Oxygen Donor ◽  
Selective Ring Opening ◽  
Benzyl Halides ◽  
First Time

An efficient and simple KO t Bu promoted selective ring-opening N-alkylation of 2-methyl-2-oxazoline or 2-(methylthio)-4,5-dihydrothiazole with benzyl halides under basic conditions has been described for the first time, which provides a convenient and practical pathway for the synthesis of versatile 2-aminoethyl acetates and N-Substituted thiazolidinones with good functional group tolerance and selectivity. KO t Bu not only plays an important role to promote this ring-opening N-alkylation, but also acts as an oxygen donor.

Sign in / Sign up

Export Citation Format

Share Document