I2-Promoted Multicomponent Dicyclization and Ring-Opening Sequences: Direct Synthesis of Benzo[e][1,4]diazepin-3-ones via Dual C–O Bond Cleavage

2019 ◽  
Vol 21 (18) ◽  
pp. 7504-7508 ◽  
Author(s):  
Xiao Geng ◽  
Can Wang ◽  
Chun Huang ◽  
Peng Zhao ◽  
You Zhou ◽  
...  
Keyword(s):  
Ring Opening ◽  
Bond Cleavage ◽  
Direct Synthesis

α-Ketophosphonates in the Synthesis of α-iminophosphonates

2020 ◽  
Vol 7 (2) ◽  
pp. 226-238
Author(s):  
Petro P. Ony`sko ◽  
Tetyana I. Chudakova ◽  
Vladimir V. Pirozhenko ◽  
Alexandr B. Rozhenko
Keyword(s):  
Bond Cleavage ◽  
Direct Synthesis ◽  
Equilibrium Mixture ◽  
Primary Amines ◽  
Alkyl Amines ◽  
Protic Solvents ◽  
Metallic Salts ◽  
Direct Preparation ◽  
Stage Synthesis ◽  
Aprotic Dipolar Solvent

The potentialities of condensation of α-ketophosphonates with primary amines for direct synthesis of α-iminophosphonates have been revealed. Diesters of α-ketophosphonic acids react with the primary amines by two competitive pathways: with a formation of α-iminophosphonates or a C-P bond cleavage resulting in a hydrogen phosphonate and an acylated amine. In many cases, the latter undesirable pathway is dominant, especially for more nucleophilic alkyl amines. Using metallic salts of α-ketophosphonates avoids the C-P bond cleavage, allowing direct preparation of α-phosphorylated imines by the reaction with primary amines. This strategy provides an atom economy single-stage synthesis of iminophosphonates – precursors of bio relevant phosphorus analogs of α-amino acids. Methyl sodium iminophosphonates, bearing aryl or heteryl substituents at the imino carbon atom exist in solutions at room temperature as an equilibrium mixture of Z- and E-isomers. A configuration of the C=N bond can be controlled by the solvent: changing the aprotic dipolar solvent DMSO-d6 by water or alcohols leads to the change from a predominant Z-isomer to almost an exclusive E-form. In contrast, diesters of the respective iminophosphonates exist in non-protic solvents predominantly in Econfiguration. The solvent effect on E-Z stereochemistry is demonstrated by DFT calculations.

Copper-Catalyzed Intramolecular α-C–H Amination via Ring-Opening Cyclization Strategy to Quinazolin-4-ones: Development and Application in Rutaecarpine Synthesis

Synthesis ◽  
2019 ◽  
Vol 51 (16) ◽  
pp. 3160-3170
Author(s):  
Srilaxmi M. Patel ◽  
Harika Chada ◽  
Sonali Biswal ◽  
Sonika Sharma ◽  
Duddu S. Sharada
Keyword(s):  
Ring Opening ◽  
Functional Group ◽  
Bond Cleavage ◽  
Isatoic Anhydride ◽  
General Method

A copper-catalyzed intramolecular α-C–H amination has been developed for the synthesis of quinazolin-4(3H)-one derivatives from commercially available isatoic anhydride and primary and secondary benzylamines via ring-opening cyclization (ROC). This method shows good functional group tolerance and allows access to a range of 2-aryl, 2-alkyl, and spiroquinazolinone derivatives. However, 2-methylquinazolin-4(3H)-one was synthesized from 2-amino-N-isopropylbenzamide by C–C bond cleavage, and N-benzyl-2-(methylamino)benzamide afforded 1-methyl-2-phenylquinazolin-4(1H)-one along with 2-phenylquinazolin-4(3H)-one by N–C bond cleavage for aromatization. It is the first general method to construct the potentially useful 2-methylquinazolin-4(3H)-one by copper-catalyzed intramolecular C–H amination. Also this ROC strategy has been successfully applied to the synthesis of quinazolinone alkaloid rutaecarpine.

Direct Synthesis of 5-Acyl-3-oxy-4-pyrones Based On Acid-­Catalyzed Acylation of Enaminodiones with Acylbenzotriazoles via Soft Enolization

Synthesis ◽  
2020 ◽  
Vol 52 (15) ◽  
pp. 2267-2276 ◽  
Author(s):  
Dmitrii L. Obydennov ◽  
Viktoria V. Viktorova ◽  
Elena V. Chernyshova ◽  
Alexander S. Shirinkin ◽  
Sergey A. Usachev ◽  
...  
Keyword(s):  
Ring Opening ◽  
Direct Synthesis ◽  
Pyrone Ring ◽  
Mild Conditions ◽  
Soft Enolization ◽  
Acid Catalyzed

A novel convenient acid-catalyzed acylation of enaminodiones with acylbenzotriazoles via soft enolization has been developed for the direct synthesis of hard-to-reach 5-acyl-3-oxy-4-pyrones. The important advantages of the reaction include broad substrate scope, mild conditions, scalability, and readily isolation of products by crystallization without the use of chromatography. Further modification of the pyrone ring and synthesis of various azaheterocycles via ring-opening transformation have been demonstrated for the preparation of potential scaffolds for inhibition of metalloenzymes.

Molybdenum-Mediated One-Pot Synthesis of Pyrazoles from Isoxazoles

Synthesis ◽  
2019 ◽  
Vol 51 (20) ◽  
pp. 3796-3804 ◽  
Author(s):  
Marine Rey ◽  
Stéphane Beaumont
Keyword(s):  
Bond Cleavage ◽  
Direct Synthesis ◽  
Molybdenum Complex ◽  
One Pot ◽  
One Pot Synthesis ◽  
Wide Range ◽  
Hydrolysis Of ◽  
Substituted Pyrazoles

A one-pot approach for the direct synthesis of substituted pyrazoles from isoxazoles is reported. The process involves isoxazole N–O bond cleavage mediated by a molybdenum complex, in situ hydrolysis of the resulting β-amino enone to the corresponding 1,3-diketone, followed by pyrazole formation in the presence of hydrazine or substituted hydrazine. Good to excellent yields and regioselectivities are obtained with nonsymmetric isoxazoles. By using readily available starting materials, a wide range of substituted pyrazoles may be synthesized by this method.

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