scholarly journals Modular synthesis of the pyrimidine core of the manzacidins by divergent Tsuji–Trost coupling

2016 ◽  
Vol 12 ◽  
pp. 1111-1121 ◽  
Author(s):  
Sebastian Bretzke ◽  
Stephan Scheeff ◽  
Felicitas Vollmeyer ◽  
Friederike Eberhagen ◽  
Frank Rominger ◽  
...  
Keyword(s):  
Phosphoric Acid ◽  
Substitution Reaction ◽  
Grignard Reagent ◽  
Design Development ◽  
Practical Application ◽  
Efficient Procedure ◽  
Modular Synthesis ◽  
Cross Metathesis ◽  
Facile Preparation ◽  
High Yields

The design, development and application of an efficient procedure for the concise synthesis of the 1,3-syn- and anti-tetrahydropyrimidine cores of manzacidins are reported. The intramolecular allylic substitution reaction of a readily available joint urea-type substrate enables the facile preparation of both diastereomers in high yields. The practical application of this approach is demonstrated in the efficient and modular preparation of the authentic heterocyclic cores of manzacidins, structurally unique bromopyrrole alkaloids of marine origin. Additional features of this route include the stereoselective generation of the central amine core with an appending quaternary center by an asymmetric addition of a Grignard reagent to a chiral tert-butanesulfinyl ketimine following an optimized Ellman protocol and a cross-metathesis of a challenging homoallylic urea substrate, which proceeds in good yields in the presence of an organic phosphoric acid.

Catalytic Asymmetric Substitution Reaction of 3-Substituted 2-Indolylmethanols with 2-Naphthols

Synthesis ◽  
2020 ◽  
Vol 52 (23) ◽  
pp. 3684-3692
Author(s):  
Feng Gao ◽  
Yu-Chen Zhang ◽  
Feng Shi ◽  
Jin-Ping Lan ◽  
Yi-Nan Lu ◽  
...  
Keyword(s):  
Phosphoric Acid ◽  
Substitution Reaction ◽  
Enantioselective Synthesis ◽  
Chiral Phosphoric Acid ◽  
Catalytic Asymmetric ◽  
High Yields

A catalytic asymmetric substitution of 3-substituted 2-indolylmethanols with 2-naphthols has been established under the catalysis of chiral phosphoric acid. By this approach, a series of structurally diversified triarylmethane derivatives were obtained in moderate to high yields with good enantioselectivities (up to 97% yield, 95:5 er). This approach not only enriches the chemistry of 2-indolylmethanol-inolved catalytic asymmetric substitutions, but also provides a useful method for the enantioselective synthesis of chiral triarylmethane derivatives.

Modular synthesis of non-conjugated N-(quinolin-8-yl) alkenyl amides via cross-metathesis

Tetrahedron ◽  
2021 ◽  
pp. 132279
Author(s):  
Hui-Qi Ni ◽  
Zi-Qi Li ◽  
Van T. Tran ◽  
Keary M. Engle
Keyword(s):  
Modular Synthesis ◽  
Cross Metathesis

scholarly journals Organocatalytic Asymmetric [2 + 4] Cycloadditions of 3-Vinylindoles with ortho-Quinone Methides

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6751
Author(s):  
Si-Jia Liu ◽  
Man-Su Tu ◽  
Kai-Yue Liu ◽  
Jia-Yi Chen ◽  
Shao-Fei Ni ◽  
...  
Keyword(s):  
Phosphoric Acid ◽  
Structural Diversity ◽  
Quinone Methides ◽  
Chiral Phosphoric Acid ◽  
Catalytic Asymmetric ◽  
High Yields ◽  
Asymmetric Cycloadditions

Catalytic asymmetric [2 + 4] cycloadditions of 3-vinylindoles with ortho-quinone methides and their precursors were carried out in the presence of chiral phosphoric acid to afford a series of indole-containing chroman derivatives with structural diversity in overall high yields (up to 98%), good diastereoselectivities (up to 93:7 dr) and moderate to excellent enantioselectivities (up to 98% ee). This approach not only enriches the chemistry of catalytic asymmetric cycloadditions involving 3-vinylindoles but is also useful for synthesizing chiral chroman derivatives.

Nucleophilic Cyclization/Electrophilic Substitution of (2,2-Dialkoxyethyl)ureas: Highly Regioselective Access to Novel 4-(Het)arylimidazolidinones and Benzo[d][1,3]diazepinones

Synthesis ◽  
2020 ◽  
Vol 52 (21) ◽  
pp. 3263-3271
Author(s):  
Andrey V. Smolobochkin ◽  
Almir S. Gazizov ◽  
Nazerke K. Otegen ◽  
Julia K. Voronina ◽  
Anna G. Strelnik ◽  
...  
Keyword(s):  
Substitution Reaction ◽  
Electrophilic Substitution ◽  
Biologically Active ◽  
Electrophilic Substitution Reaction ◽  
Reaction Sequence ◽  
Active Compounds ◽  
Acid Catalyzed ◽  
High Yields ◽  
Nucleophilic Cyclization ◽  
Mechanism Of The Reaction

Imidazolidin-2-one and 1,3-benzodiazepin-2-one scaffolds are structural motifs of many biologically active compounds. Herein, we report a highly regioselective acid-catalyzed intramolecular nucleophilic cyclization/intermolecular electrophilic substitution reaction sequence of (2,2-dialkoxyethyl)ureas. The reaction benefits from readily available starting materials, a simple workup procedure, moderate to high yields of target compounds, and provides a convenient entry to previously unknown 4-(het)arylimidazolidinones and 5-(het)arylbenzodiazepinones. The proposed mechanism of the reaction is also discussed.

Highly Enantioselective Biginelli Reaction of Aliphatic Aldehydes Catalyzed by Chiral Phosphoric Acids

Synlett ◽  
2017 ◽  
Vol 28 (15) ◽  
pp. 2041-2045 ◽  
Author(s):  
Yongbiao Guo ◽  
Chuanpin Zou ◽  
Zhenhua Gao ◽  
Xiangyan Meng ◽  
Guilan Huang ◽  
...  
Keyword(s):  
Phosphoric Acid ◽  
Biginelli Reaction ◽  
Aliphatic Aldehyde ◽  
Reaction Conditions ◽  
Aliphatic Aldehydes ◽  
Keto Ester ◽  
Chiral Phosphoric Acid ◽  
Three Component Reaction ◽  
High Yields ◽  
Phosphoric Acids

Several chiral phosphoric acids were evaluated as organocatalysts for the enantioselective Biginelli reaction of aliphatic aldehydes. With a chiral phosphoric acid derived from 3,3′-bis(3,5-di-tert-butyl-4-methoxyphenyl)-1,1′-binaphthalene-2,2′-diol, and after extensive optimization of the reaction conditions, the corresponding dihydropyrimidines were obtained in moderate to high yields with 73–87% ee by a three-component reaction of an aliphatic aldehyde, urea, and a β-keto ester.

PREPARATION OF KETENE FROM GLACIAL ACETIC ACID. METHYL ACETATE, AND ETHYL ACETATE

1952 ◽  
Vol 30 (4) ◽  
pp. 332-347 ◽  
Author(s):  
K. K. Georgieff
Keyword(s):  
Acetic Acid ◽  
Phosphoric Acid ◽  
Ethyl Acetate ◽  
Methyl Acetate ◽  
Maximum Yield ◽  
Acid Catalyst ◽  
Absolute Maximum ◽  
Triethyl Phosphate ◽  
Maximum Conversion ◽  
High Yields

Laboratory studies were carried out to determine whether methyl and ethyl acetates could be pyrolyzed to give yields and conversions to ketene comparable to those obtainable from acetic acid. Acetic acid was pyrolyzed to ketene and water in the presence of 0.33% triethyl phosphate or phosphoric acid catalyst at 680°–760 °C. and 140–160 mm. Hg absolute. Maximum yield obtained was 80.6% and maximum conversion 34.5%. Methyl acetate was cracked to ketene and methanol at 610°–685 °C. and 95–400 mm. absolute, using triethyl phosphate, phosphoric acid, sulphuric acid, dimethyl sulphate, butyl borate, and silica gelboric acid as catalysts. High yields could be obtained only with phosphates in 2–3% concentration. Maximum yield to ketene, including ketene recovered as acetic acid, was 76% (conversion 31–34%). Maximum yield to methanol was 81.3% (conversion 33–34%). Methyl acetate containing 18% methanol was also cracked but results were poorer. Ethyl acetate, in the presence of 0.33% triethyl phosphate, was pyrolyzed to ketene, ethylene, and water at 630°–685 °C. and 140–190 mm. absolute. Maximum yield of ketene, including ketene recovered as acetic acid, was 85.8%. Maximum conversion to ketene was 35.4% and to ketene plus acetic acid 85.7%. Yields to ethylene were nearly quantitative.

scholarly journals Organocatalytic asymmetric selenofunctionalization of tryptamine for the synthesis of hexahydropyrrolo[2,3-b]indole derivatives

2013 ◽  
Vol 9 ◽  
pp. 1559-1564 ◽  
Author(s):  
Qiang Wei ◽  
Ya-Yi Wang ◽  
Yu-Liu Du ◽  
Liu-Zhu Gong
Keyword(s):  
Phosphoric Acid ◽  
Indole Derivatives ◽  
Chiral Phosphoric Acid ◽  
Acid Catalyzed ◽  
High Yields

A chiral phosphoric acid-catalyzed selenofunctionalization of tryptamine derivatives provides access to 3a-(phenylselenyl)-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole derivatives in high yields and with synthetically useful levels of enantioselectivity (up to 89% ee).

scholarly journals Organosolv delignification of residual plantation willow bark after extractive removal

2020 ◽  
Author(s):  
Matiss Pals ◽  
◽  
Liga Lauberte ◽  
Alexandr Arshanitsa ◽  
Laima Vevere ◽  
...  
Keyword(s):  
Effect Of Temperature ◽  
Insoluble Residue ◽  
Optimal Conditions ◽  
Practical Application ◽  
Residual Biomass ◽  
Main Cell ◽  
Willow Bark ◽  
High Yields ◽  
Wall Components ◽  
Comprehensive Characterization

Plantation willows are commonly grown plants which are widely used for energetic purposes that does not correspond completely to its potential. To fully integrate this resource into biorefinery scheme, it is necessary to study optimal conditions of willow bark processing, aimed for separation of bark components, their comprehensive characterization and profitable practical application. Extraction of secondary metabolites is well known approach for bark processing. But the separation of the main cell wall components including lignin from the residual biomass is less studied. In this work plantation residual willow bark after extractives separation by two different solvents (acetone and ethanolwater) was used as a feedstock for Organosolv delignification. Effect of temperature and catalyst used on the yield and properties of lignin isolated from residual bark by ethanol-water treatment was studied. It was possible to obtain pure lignin with high yields (up to 41%) that has the potential to be used for bio-plastic producing. Insoluble residue after delignification was carbohydrate rich (up to 80%) feedstock allowing its practical use for bioethanol producing.

Construction of chiral chroman scaffolds via catalytic asymmetric (4 + 2) cyclizations of para-quinone methide derivatives with 3-vinylindoles

2020 ◽  
Vol 18 (28) ◽  
pp. 5388-5399 ◽  
Author(s):  
Shu-Fang Wu ◽  
Man-Su Tu ◽  
Qing-Qing Hang ◽  
Shu Zhang ◽  
Haixia Ding ◽  
...  
Keyword(s):  
Phosphoric Acid ◽  
Quinone Methide ◽  
Title Reaction ◽  
Chiral Phosphoric Acid ◽  
Catalytic Asymmetric ◽  
High Yields

The title reaction has been established in the presence of chiral phosphoric acid, affording chiral chroman derivatives bearing an indole moiety in high yields and with moderate to good stereoselectivities.

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