Protecting groups for the pyrrole and indole nitrogen atom. The [2-(trimethylsilyl)ethoxy]methyl moiety. Lithiation of 1-[[2-(trimethylsilyl)ethoxy]methyl]pyrrole

1984 ◽  
Vol 49 (1) ◽  
pp. 203-205 ◽  
Author(s):  
Joseph M. Muchowski ◽  
Dennis R. Solas
Keyword(s):  
Nitrogen Atom ◽  
Protecting Groups

Protecting groups for the pyrrole nitrogen atom. The 2-chloroethyl, 2-phenylsulfonylethyl, and related moieties

1983 ◽  
Vol 61 (8) ◽  
pp. 1697-1702 ◽  
Author(s):  
Carlos Gonzalez ◽  
Robert Greenhouse ◽  
Ramon Tallabs ◽  
Joseph M. Muchowski
Keyword(s):  
Nitrogen Atom ◽  
Michael Reaction ◽  
Phase Transfer ◽  
Homogeneous Solution ◽  
Sodium Hydride ◽  
Protecting Groups ◽  
Protecting Group ◽  
One Pot ◽  
Subsequent Degradation ◽  
Pyrrole Nitrogen

The 2-chloroethyl and 2-phenylsulfonylethyl moieties are versatile protecting groups for the pyrrole nitrogen atom. The 2-chloroethyl group is easily attached under phase transfer conditions using 1,2-dichloroethane. The 2-phenylsulfonylethyl moiety is readily appended under both phase transfer and homogeneous solution conditions using 2-phenylsulfonylcthyl chloride 5. Deprotection of the N-(2-chloroethyl)pyrroles is accomplished by means of efficient three-step, one-pot sequences via the N-vinyl compounds 3 and subsequent degradation of the N-(1-hydroxyethyl) compounds 4 or the acctoxymercuration derivatives 5 obtained therefrom. The 2-phenylsulfonylethyl group is excised by a reverse Michael reaction using sodium hydride or DBN as the base.The utility of the 2-chloroethyl protecting group is exemplified in a synthesis of benzyl cyclopenta[b] |pyrrole-5-carboxylate 13 from 1-(2-chloroethyl)-4-oxotetrahydroindolc 2d.

scholarly journals Synthesis, Reactivity and Stability of Aryl Halide Protecting Groups towards Di-Substituted Pyridines

2018 ◽  
Vol 16 (1) ◽  
pp. 53
Author(s):  
Ptoton Mnangat Brian ◽  
Peter Musau
Keyword(s):  
Nitrogen Atom ◽  
Pyridine Ring ◽  
Aryl Halide ◽  
Protecting Groups ◽  
Pyridinium Salts ◽  
Substituted Pyridines ◽  
Benzyl Halides

This paper reports the synthesis and reactivity of different Benzyl derivative protecting groups. The synthesis and stability of Benzyl halides, 4-methoxybenzyl halides, 3,5-dimethoxybenzyl halides, 3,4-dimethoxybenzyl halides, 3,4,5-trimethoxybenzyl halide protecting groups and their reactivity towards nitrogen atom of a di-substituted pyridine ring in formation of pyridinium salts is also reported.

Nitrogen Atom Densities in Rare Gas Diluted N2 Plasmas with Capacitive and Inductive Coupling

2008 ◽  
Vol 128 (10) ◽  
pp. 615-618 ◽  
Author(s):  
Takeshi Kitajima ◽  
Akihiro Kubota ◽  
Toshiki Nakano
Keyword(s):  
Nitrogen Atom ◽  
Inductive Coupling ◽  
Rare Gas

Visible Light-Mediated Oxidative Debenzylation

2020 ◽  
Author(s):  
Cristian Cavedon ◽  
Eric T. Sletten ◽  
Amiera Madani ◽  
Olaf Niemeyer ◽  
Peter H. Seeberger ◽  
...  
Keyword(s):  
Reaction Time ◽  
Visible Light ◽  
Functional Groups ◽  
Continuous Flow ◽  
Protecting Groups ◽  
Benzyl Ether ◽  
Complex Molecules ◽  
Protective Groups ◽  
Benzyl Ethers ◽  
Harsh Conditions

Protecting groups are key in the synthesis of complex molecules such as carbohydrates to distinguish functional groups of similar reactivity. The harsh conditions required to cleave stable benzyl ether protective groups are not compatible with many other protective and functional groups. The mild, visible light-mediated debenzylation disclosed here renders benzyl ethers orthogonal protective groups. Key to success is the use of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as stoichiometric or catalytic photooxidant such that benzyl ethers can be cleaved in the presence of azides, alkenes, and alkynes. The reaction time for this transformation can be reduced from hours to minutes in continuous flow. <br>

A Facile, Efficient and Selective Deprotection of P - Methoxy Benzyl Ethers Using Zinc (II) Trifluoromethanesulfonate

2019 ◽  
Vol 16 (12) ◽  
pp. 955-958
Author(s):  
Reddymasu Sireesha ◽  
Reddymasu Sreenivasulu ◽  
Choragudi Chandrasekhar ◽  
Mannam Subba Rao
Keyword(s):  
Room Temperature ◽  
Protecting Groups ◽  
Side Reactions ◽  
Reaction Conditions ◽  
Acid Sensitivity ◽  
Time Period ◽  
Protective Groups ◽  
Benzyl Ethers ◽  
Last Stage ◽  
Zinc Triflate

: Deprotection is significant and conducted over mild reaction conditions, in order to restrict any more side reactions with sensitive functional groups as well as racemization or epimerization of stereo center because the protective groups are often cleaved at last stage in the synthesis. P - Methoxy benzyl (PMB) ether appears unique due to its easy introduction and removal than the other benzyl ether protecting groups. A facile, efficient and highly selective cleavage of P - methoxy benzyl ethers was reported by using 20 mole% Zinc (II) Trifluoromethanesulfonate at room temperature in acetonitrile solvent over 15-120 min. time period. To study the generality of this methodology, several PMB ethers were prepared from a variety of substrates having different protecting groups and subjected to deprotection of PMB ethers using Zn(OTf)2 in acetonitrile. In this methodology, zinc triflate cleaves only PMB ethers without affecting acid sensitivity, base sensitivity and also chiral epoxide groups.

Hafnium(IV) Chloride Catalyzes Highly Efficient Acetalization of Carbonyl Compounds

2019 ◽  
Vol 16 (6) ◽  
pp. 913-920 ◽  
Author(s):  
Israel Bonilla-Landa ◽  
Emizael López-Hernández ◽  
Felipe Barrera-Méndez ◽  
Nadia C. Salas ◽  
José L. Olivares-Romero
Keyword(s):  
Microwave Heating ◽  
Reaction Times ◽  
Protecting Groups ◽  
Catalyst Loading ◽  
Selective Protection ◽  
Highly Efficient ◽  
Aldehydes And Ketones ◽  
High Yields ◽  
Novel Catalyst ◽  
Acid Labile

Background: Hafnium(IV) tetrachloride efficiently catalyzes the protection of a variety of aldehydes and ketones, including benzophenone, acetophenone, and cyclohexanone, to the corresponding dimethyl acetals and 1,3-dioxolanes, under microwave heating. Substrates possessing acid-labile protecting groups (TBDPS and Boc) chemoselectively generated the corresponding acetal/ketal in excellent yields. Aim and Objective: In this study. the selective protection of aldehydes and ketones using a Hafnium(IV) chloride, which is a novel catalyst, under microwave heating was observed. Hence, it is imperative to find suitable conditions to promote the protection reaction in high yields and short reaction times. This study was undertaken not only to find a novel catalyst but also to perform the reaction with substrates bearing acid-labile protecting groups, and study the more challenging ketones as benzophenone. Materials and Methods: Using a microwave synthesis reactor Monowave 400 of Anton Paar, the protection reaction was performed on a raging temperature of 100°C ±1, a pressure of 2.9 bar, and an electric power of 50 W. More than 40 substrates have been screened and protected, not only the aldehydes were protected in high yields but also the more challenging ketones such as benzophenone were protected. All the products were purified by simple flash column chromatography, using silica gel and hexanes/ethyl acetate (90:10) as eluents. Finally, the protected substrates were characterized by NMR 1H, 13C and APCI-HRMS-QTOF. Results: Preliminary screening allowed us to find that 5 mol % of the catalyst is enough to furnish the protected aldehyde or ketone in up to 99% yield. Also it was found that substrates with a variety of substitutions on the aromatic ring (aldehyde or ketone), that include electron-withdrawing and electrondonating group, can be protected using this methodology in high yields. The more challenging cyclic ketones were also protected in up to 86% yield. It was found that trimethyl orthoformate is a very good additive to obtain the protected acetophenone. Finally, the protection of aldehydes with sensitive functional groups was performed. Indeed, it was found that substrates bearing acid labile groups such as Boc and TBDPS, chemoselectively generated the corresponding acetal/ketal compound while keeping the protective groups intact in up to 73% yield. Conclusion: Hafnium(IV) chloride as a catalyst provides a simple, highly efficient, and general chemoselective methodology for the protection of a variety of structurally diverse aldehydes and ketones. The major advantages offered by this method are: high yields, low catalyst loading, air-stability, and non-toxicity.

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