Synthesis of Tetrahydroisoquinolines by Visible-Light-Mediated 6-exo-trig Cyclization of α-Aminoalkyl Radicals

Synlett ◽  
2019 ◽  
Vol 30 (15) ◽  
pp. 1825-1829 ◽  
Author(s):  
Michael Grübel ◽  
Christian Jandl ◽  
Thorsten Bach
Keyword(s):  
Crystal Structure ◽  
Direct Electron Transfer ◽  
Metal Catalyst ◽  
Cesium Carbonate ◽  
Reaction Conditions ◽  
Relative Configuration ◽  
Radical Bromination ◽  
Step Procedure ◽  
Michael Acceptors ◽  
High Yields

Starting from the respective tertiary α-silylmethyl amines, the intramolecular cyclization of α-aminoalkyl radicals to Michael acceptors produced tetrahydroisoquinolines. The reaction conditions included the use of 5 mol% of an iridium photoredox catalyst, dimethylformamide as the solvent, and equimolar amounts of water and cesium carbonate as the additives. 13 substrates were synthesized from ortho-alkylbenzaldehydes in a three-step procedure involving a carbonyl condensation, a radical bromination, and a substitution by a secondary α-silylmethyl amine. After optimization of the photocyclization, the reaction delivered tetrahydroisoquinolines in moderate to high yields (41–83%). A facial diastereoselectivity (dr ≅ 80:20) was observed with chiral substrates and a crystal structure provided evidence for the relative configuration of the major diastereoisomer. A catalytic cycle with direct electron transfer to the photoexcited metal catalyst is proposed.

Synthesis of N-Aryl-4-arylhexahydroquinoline Derivatives by Reaction of Cyclic Enaminones with Arylidenemalononitriles in DMSO

Synthesis ◽  
2020 ◽  
Author(s):  
Takeshi Oriyama ◽  
Wei Han ◽  
Chika Inoue ◽  
Tsunaki Onizawa
Keyword(s):  
Transition Metal ◽  
Dimethyl Sulfoxide ◽  
Molecular Sieves ◽  
Metal Catalyst ◽  
Reaction Conditions ◽  
Transition Metal Catalyst ◽  
Cyclic Enaminones ◽  
High Yields

AbstractThe reaction of cyclic enaminones with arylidenemalono­nitriles was carried out in the presence of 13X molecular sieves in dimethyl sulfoxide. Under these mild reaction conditions, various bioactive N-aryl-4-arylhexahydroquinoline derivatives were obtained in high yields without the necessity of using transition-metal catalyst, organobase, or reflux conditions.

1,3-Dipolar [3+3] Cycloaddition of 1,4-Benzodiazepinone-Based Nitrones with α-Halohydroxamates for Diastereoselective Synthesis of Novel d-Edge Heterocycle-Fused 1,4-Benzodiazepinones

Synlett ◽  
2021 ◽  
Author(s):  
Hong-Wu Zhao ◽  
Heng Zhang ◽  
Lu-Yu Cai ◽  
Zhe Tang ◽  
Xiao-Zu Fan ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Reaction Mechanism ◽  
Single Crystal ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
Diastereoselective Synthesis ◽  
Reaction Conditions ◽  
Relative Configuration ◽  
X Ray ◽  
Single Crystal Structure Analysis

Promoted by K2CO3 (2.0 equiv), the 1,3-dipolar [3+3] cycloaddition between 1, 4-benzodiazepinone-based nitrones and α-halohydroxamates processed smoothly under the mild reaction conditions and delivered structurally novel and complex cis or trans-configured d-edge-heterocycle-fused 1,4-benzodiazepinones in up to >99% isolated yield with >20:1 dr. The relative configuration of the title chemical entities was clearly identified with the use of X-ray single crystal structure analysis. The reaction mechanism was assumed to interpret the diastereoselective production of the obtained cis or trans-configured d-edge-heterocycle-fused 1, 4-benzodiazepinones.

Diversity Oriented Synthesis of 4H-Pyrimido[2,1-b]benzothiazole Derivatives via Biginellis Reaction: A Review

2018 ◽  
Vol 21 (4) ◽  
pp. 236-253 ◽  
Author(s):  
Divyani Gandhi ◽  
Priyanka Kalal ◽  
Prakash Prajapat ◽  
Dinesh Kumar Agarwal ◽  
Shikha Agarwal
Keyword(s):  
Phase Transfer ◽  
Reaction Times ◽  
Reaction Medium ◽  
Combinatorial Libraries ◽  
Acid Catalyst ◽  
Metal Catalyst ◽  
Reaction Conditions ◽  
Benzothiazole Derivatives ◽  
Nano Catalyst ◽  
High Yields

Background: Heterocycles have extended into widespread use for generating large collection of molecules in multi-component reactions. The development of new strategies for fused pyrimidobenzothiazole system has remained a highly attractive but challenging proposition for scientists working all around. Objective: The main objective of this work is to explore the utility of different catalysts as an ecofriendly reaction medium for green Biginellis reaction. Method: A detailed study of Biginellis reactions using various catalysts was done using different research tools. The methods involved reaction of equimolar mixture of benzothiazole, 1,3-diketone and aldehyde as reactants by conventional and greener pathways via Knoevenagal condensation. Results: The present review has several significant advantages for the scientists regarding green synthesis viz. green conditions, short reaction times, high yields, clean reaction conditions, easy isolation of products, simple work-up procedure and mild reaction conditions. Conclusion: Our report gives an overview of the combinatorial libraries for fused benzothiazole entities using metal catalyst, acid catalyst, ionic liquids, phase transfer catalyst, nano catalyst, etc.

Synthesis and Crystal Structure of 4-[5-(2-Bromophenyl)-1,3,4-Thiadiazol-2-Ylthio]-2-(trifluoromethyl)thieno[2,3-d]pyrimidine

2014 ◽  
Vol 887-888 ◽  
pp. 703-706
Author(s):  
Ping Yang ◽  
Hui Gao ◽  
Yao Nie ◽  
Zhen Zeng ◽  
Jin Shun Zhao ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Trifluoroacetic Acid ◽  
X Ray Diffraction ◽  
Reaction Conditions ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
H Nmr ◽  
Planar Conformation ◽  
Step Procedure ◽  
Title Molecule

4-[5-(2-Bromophenyl)-1,3,4-thiadiazol-2-ylthio]-2-(trifluoromethyl)thieno[2,3-d]pyrimidine was synthesized by a facile three-step procedure, including the cyclization of 2-aminothiophene-3-carbonitrile with trifluoroacetic acid, chlorination and nucleophilic substitution reaction. This protocol offers such advantages as mild reaction conditions, simple purification and good yields. The structure of the product was characterized by 1H NMR, MS, elemental analysis and single-crystal X-ray diffraction. X-Ray diffraction analysis reveals that the title molecule essentially assumes a planar conformation except for the F atoms.

The Immobilized Copper on Nickel Ferrite: A Magnetically Superior Nanocatalyst for Chemoselective and Knoevenagel Synthesis of Bisdimedones and 1,8-Dioxo-octahydroxanthenes under Solvent-Free Conditions

2019 ◽  
Vol 16 (6) ◽  
pp. 939-947 ◽  
Author(s):  
Behzad Zeynizadeh ◽  
Soleiman Rahmani ◽  
Arezu Hallaj
Keyword(s):  
Catalytic Activity ◽  
Aromatic Aldehydes ◽  
Catalyst System ◽  
Solvent Free ◽  
Biologically Active ◽  
Knoevenagel Reaction ◽  
Reaction Conditions ◽  
Step Procedure ◽  
Solvent Free Conditions ◽  
High Yields

Aim and Objective: Nowadays, bisdimedones and 1,8-dioxo-octahydroxanthenes are considered as biologically active materials. Due to this, the synthesis of the mentioned materials is the subject of more interest. Although most of the reported methods have their own merits, however, they generally require the use of expensive reagents, hazardous organic solvents, a tedious workup procedure and reduced recyclability of the applied catalyst system. Overcoming of the above mentioned drawbacks, therefore, encouraged us to investigate the capability of nanostructured NiFe2O4@Cu towards the synthesis of bisdimedones and 1,8- dioxo-octahydroxanthenes under green reaction conditions. Materials and Methods: Nanoparticles of NiFe2O4@Cu were prepared via a two-step procedure including the preparation of NiFe2O4 by solid-state grinding of Ni(OAc)2·4H2O and Fe(NO3)3·9H2O in the presence of NaOH followed by the immobilization of Cu(0) on the surface of NiFe2O4 nucleus via hydrazine hydrate reduction of Cu(NO3)2·3H2O. Results: After the synthesis of NiFe2O4@Cu, the catalytic activity of the Cu-nanocatalyst towards Knoevenagel reaction of aromatic aldehydes with dimedone under different reaction conditions was investigated. The examinations showed that using the molar equivalents of aromatic aldehydes (1 mmol) and dimedone (2 mmol) in the presence of 0.15 g NiFe2O4@Cu under solvent-free conditions chemoselectively afforded structurally different bisdimedone products at 60°C and 1,8-dioxo-octahydroxanthenes at 120°C. Conclusion: In this study, magnetically, nanoparticles of NiFe2O4@Cu were prepared and then characterized using different analyses. The catalytic activity of the prepared Cu-nanocatalyst was also studied towards solvent-free Knoevenagel condensation of aromatic aldehydes with dimedone. All the reactions were carried out within 15-240 min to afford bisdimedone and 1,8-dioxo-octahydroxanthene products in high yields.

Temperature Dependent Green Synthesis of 3-Carboxycoumarins and 3,4-unsubstituted Coumarins

2019 ◽  
Vol 16 (1) ◽  
pp. 130-135 ◽  
Author(s):  
Jack van Schijndel ◽  
Dennis Molendijk ◽  
Luiz Alberto Canalle ◽  
Erik Theodorus Rump ◽  
Jan Meuldijk
Keyword(s):  
Knoevenagel Condensation ◽  
Ammonium Bicarbonate ◽  
Solvent Free ◽  
Temperature Dependent ◽  
Step Procedure ◽  
Synthetic Routes ◽  
High Yields ◽  
Temperature Optima ◽  
Solvent Free Synthesis ◽  
Full Conversion

Aim and Objective: Because of the low abundance of 3,4-unsubstituted coumarins in plants combined with the complex purification process required, synthetic routes towards 3,4-unsubstituted coumarins are especially valuable. In the present work, we explore the possibilities of a solvent-free Green Knoevenagel condensation on various 2-hydroxybenzaldehyde derivatives and malonic acid without the use of toxic organocatalysts like pyridine and piperidine but only use ammonium bicarbonate as the catalyst. Materials and Methods: To investigate the scope of the Green Knoevenagel condensation for the synthesis of 3,4-unsubstituted coumarins, various 2-hydroxybenzaldehyde derivatives were screened as starting material in the optimized two-step procedure developed for 2-hydroxybenzaldehyde. </P><P> Results: This study shows that the intramolecular esterification and the decarboxylation are in competition, but show different temperature optima. In order to suppress premature decarboxylation and maximize the yield of coumarin, a two-step procedure was adopted. The reaction mixture containing ammonium bicarbonate is initially kept at 90ºC for 1 hour. After completion of the cyclization, the temperature of the reaction mixture is increased to 140ºC for 2 hours. Following this protocol, coumarin could be isolated with a yield of 95%. Conclusion: A two-step procedure for the solvent-free synthesis of several 3,4-unsubstituted coumarins was developed using ammonium bicarbonate, resulting in high yields of the desired products. Moreover, this procedure has a low E-factor and is, therefore an environmental friendly reaction in line with the principles of Green Chemistry. It was shown that by initially capping the temperature at 90ºC, premature decarboxylation can be suppressed. After full conversion to the intermediate 3-carboxycoumarin, the temperature can be increased to 140ºC finalizing the reaction. Ammonium bicarbonate was shown to catalyze both the Green Knoevenagel condensation and the decarboxylation step.

Novel One-pot Synthesis of Pyranocarbazole Derivatives via an Isocyanide-based Three-component Reaction

2020 ◽  
Vol 17 ◽  
Author(s):  
Visarapu Malathi ◽  
Pedavenkatagari Narayana Reddy ◽  
Pannala Padmaja
Keyword(s):  
Efficient Method ◽  
Atom Economy ◽  
Reaction Conditions ◽  
One Pot ◽  
Catalyst Free ◽  
One Pot Synthesis ◽  
Three Component Reaction ◽  
High Yields

Abstract:: An efficient method has been developed for the synthesis of new pyrano[3,2-c] and pyrano[3,2-a]carbazole de-rivatives via a three component reaction of 4-hydroxycarbazole or 2-hydroxycarbazole, isocyanides, and dialkylacetylenedi-carboxylates. Noteworthy features of this protocol include mild reaction conditions, catalyst-free, high atom-economy and high yields.

scholarly journals A two step synthesis of a key unit B precursor of cryptophycins by asymmetric hydrogenation

2011 ◽  
Vol 7 ◽  
pp. 243-245 ◽  
Author(s):  
Benedikt Sammet ◽  
Mathilde Brax ◽  
Norbert Sewald
Keyword(s):  
Asymmetric Hydrogenation ◽  
Synthetic Route ◽  
Reaction Conditions ◽  
High Yields

A novel highly enantioselective two step access to a unit B precursor of cryptophycins in good yields from commercially available starting materials has been developed. The key step is an asymmetric hydrogenation using the commercially available [(COD)Rh-(R,R)-Et-DuPhos]BF4 catalyst. The synthetic route provides the advantage of less synthetic steps, proceeds with high yields and enantioselectivity, and avoids hazardous reaction conditions.

scholarly journals A Simple and Efficient Synthesis of Highly Substituted Indeno[1,2-b]pyrrole and Acenaphtho[1,2-b]pyrrole Derivatives by Tandem Three-Component Reactions

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 3031 ◽  
Author(s):  
Xiaodong Tang ◽  
Songlei Zhu ◽  
Ying Ma ◽  
Ren Wen ◽  
Lanqi Cen ◽  
...  
Keyword(s):  
Environmentally Benign ◽  
Efficient Synthesis ◽  
Reaction Conditions ◽  
Dicarbonyl Compounds ◽  
Pyrrole Derivatives ◽  
Three Component Reaction ◽  
High Yields ◽  
Operational Simplicity

A green, convenient and tandem procedure for the efficient synthesis of highly substituted indeno[1,2-b]pyrrole and acenaphtho[1,2-b]pyrrole derivatives by domino three-component reaction of tryptamine/benzylamine, 1,3-dicarbonyl compounds and ninhydrin/ acenaphthenequinone is described. The significant features of this procedure were characterized by mild reaction conditions, high yields, operational simplicity and it being environmentally benign.

The Meisenheimer rearrangement in heterocyclic synthesis. II. Synthesis and X-ray crystal structure of a tetrahydro-1H-2,3-benzoxazocine and preparation of a hexahydro-2,3-benzoxazonine

1980 ◽  
Vol 33 (6) ◽  
pp. 1323 ◽  
Author(s):  
JB Bremner ◽  
EJ Browne ◽  
PE Davies ◽  
CLWAH Raston
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Acetic Acid ◽  
Crystal And Molecular Structure ◽  
Phosphorus Oxychloride ◽  
Crystallographic Analysis ◽  
Heterocyclic Synthesis ◽  
Reaction Conditions ◽  
X Ray ◽  
Heterocyclic Derivatives

The heterocyclic derivatives, 8,9-dimethoxy-3-methyl-1-phenyl-3,4,5,6- tetrahydro-1H-2,3-benzoxazocine(3a) and 9,10-dimethoxy-3-methyl-1- phenyl-1,3,4,5,6,7-hexahydro-2,3-benzoxazonine (3b),examples of two new ring systems, have been prepared by Meisenheimer rearrangement of the corresponding 2-benzazepine and 2-benzazocine N-oxide derivatives (2a) and (2b). The Bischler-Napieralski-type cyclization reaction was used in the preparation of the tertiary amine precursors of these N-oxides reaction conditions for the cyclization were critical and phosphorus oxychloride in refluxing butanenitrile was found to give the best yields of the seven- or eight-membered cyclic imine intermediates. Reductive cleavage of the benzoxazocine derivative (3a) with zinc in acetic acid followed by N-methylation gave the expected product, [2-{3- (dimethylamino)propyl}-4,5-di-methoxyphenyl]phenylmethanol (12). The crystal and molecular structure of (3a) has been determined by X-ray crystallographic analysis.

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