Regioselectivity Patterns in Radical Cyclization of Diosphenol Derivatives with Different Ring Size: A Combined Experimental and DFT Study

2021 ◽  
Vol 6 (8) ◽  
pp. 1748-1755
Author(s):  
Esra Boz ◽  
Hafize Özcan ◽  
Ömer Zaim ◽  
Nurcan Ş. Tüzün
Keyword(s):  
Radical Cyclization ◽  
Dft Study ◽  
Ring Size

scholarly journals Effect of ring rize on photoisomerization properties of stiff stilbene macrocycles

2019 ◽  
Vol 15 ◽  
pp. 2408-2418 ◽  
Author(s):  
Sandra Olsson ◽  
Óscar Benito Pérez ◽  
Magnus Blom ◽  
Adolf Gogoll
Keyword(s):  
Dft Calculations ◽  
Energy Difference ◽  
Carbon Chain ◽  
Experimental Results ◽  
Dft Study ◽  
Ring Size ◽  
Flexible Chain ◽  
Photochemical Properties

A series of stiff stilbene macrocycles have been studied to investigate the possible impact of the macrocycle ring size on their photodynamic properties. The results show that reducing the ring size counteracts the photoisomerization ability of the macrocycles. However, even the smallest macrocycle studied (stiff stilbene subunits linked by a six carbon chain) showed some degree of isomerization when irradiated. DFT calculations of the energy differences between the E- and Z-isomers show the same trend as the experimental results. Interestingly the DFT study highlights that the energy difference between the E- and Z-isomers of even the largest macrocycle (linked by a twelve carbon chain) is significantly higher than that of the stiff stilbene unit itself. In general, it is indicated that addition of even a flexible chain to the stiff stilbene unit may significantly affect its photochemical properties and increase the photostability of the resulting macrocycle.

Ring-expanded iridium and rhodiumN-heterocyclic carbene complexes: a comparative DFT study of heterocycle ring size and metal center diversity

2017 ◽  
Vol 70 (7) ◽  
pp. 1270-1284 ◽  
Author(s):  
E. Ö. Karaca ◽  
M. Akkoç ◽  
E. Öz ◽  
S. Altin ◽  
V. Dorcet ◽  
...  
Keyword(s):  
Metal Center ◽  
Dft Study ◽  
Ring Size ◽  
Carbene Complexes

Cascade Radical Cyclization to Vinylogous Carbonates/Carbamates for the Synthesis of Oxa- and Aza-Angular Triquinanes: Diastereoselectivity Depends on the Ring Size of Radical Precursor

Synthesis ◽  
2018 ◽  
Vol 50 (15) ◽  
pp. 2954-2967 ◽  
Author(s):  
Santosh Gharpure ◽  
P. Niranjana ◽  
Suheel Porwal
Keyword(s):  
Radical Cyclization ◽  
Ring Size ◽  
Efficient Strategy

An efficient strategy was developed for the stereoselective construction of oxa- and aza-angular triquinanes employing a cascade 5-exo-trig radical cyclization to vinylogous carbonates and carbamates. The radical precursors are readily prepared from 2-(hydroxymethyl)cyclopentenone/cyclohexenones. High diastereoselectivity is observed for the formation of angular oxa- and azatriquinanes. Diastereoselectivity drops when six-membered radical precursors are used. The strategy is found to be useful to incorporate synthetically challenging moieties such as spiroindoline, lactone-bearing, and uracil-fused angular triquinanes in a concise manner.

scholarly journals [Co(TPP)]-Catalyzed Formation of Substituted Piperidines

2019 ◽  
Author(s):  
Bas de Bruin ◽  
Marianne Lankelma ◽  
Astrid M. Olivares
Keyword(s):  
Radical Cyclization ◽  
Ring Closure ◽  
Radical Formation ◽  
Dft Study ◽  
Powerful Method ◽  
Radical Intermediates ◽  
Benzyl Radical ◽  
Mechanistic Understanding ◽  
High Yields

Radical cyclization via cobalt(III)–carbene radical intermediates is a powerful method for the synthesis of (hetero)cycles. Building on the recently reported synthesis of N-heterocyclic pyrrolidines catalyzed by Co(II) porphyrins, we herein report the [Co(TPP)]-catalyzed formation of desirable six membered N heterocyclic piperidines, directly from linear aldehydes. Piperidines were obtained in overall high yields, with linear alkenes being formed as side products in small amounts. A DFT study was performed to gain a deeper mechanistic understanding of the cobalt(II)-porphyrin-catalyzed formation of pyrrolidines, piperidines and linear alkenes. The calculations show that the alkenes are unlikely to be formed through 1,2-HAT. Instead, the calculations are consistent with a pathway involving benzyl radical formation followed by radical rebound ring-closure to form the piperidines. Competitive 1,5-HAT from the beta-position to the benzyl radical explains the formation of linear alkenes.<br>

scholarly journals [Co(TPP)]-Catalyzed Formation of Substituted Piperidines

2019 ◽  
Author(s):  
Bas de Bruin ◽  
Marianne Lankelma ◽  
Astrid M. Olivares
Keyword(s):  
Radical Cyclization ◽  
Ring Closure ◽  
Radical Formation ◽  
Dft Study ◽  
Powerful Method ◽  
Radical Intermediates ◽  
Benzyl Radical ◽  
Mechanistic Understanding ◽  
High Yields

Radical cyclization via cobalt(III)–carbene radical intermediates is a powerful method for the synthesis of (hetero)cycles. Building on the recently reported synthesis of N-heterocyclic pyrrolidines catalyzed by Co(II) porphyrins, we herein report the [Co(TPP)]-catalyzed formation of desirable six membered N heterocyclic piperidines, directly from linear aldehydes. Piperidines were obtained in overall high yields, with linear alkenes being formed as side products in small amounts. A DFT study was performed to gain a deeper mechanistic understanding of the cobalt(II)-porphyrin-catalyzed formation of pyrrolidines, piperidines and linear alkenes. The calculations show that the alkenes are unlikely to be formed through 1,2-HAT. Instead, the calculations are consistent with a pathway involving benzyl radical formation followed by radical rebound ring-closure to form the piperidines. Competitive 1,5-HAT from the beta-position to the benzyl radical explains the formation of linear alkenes.<br>

scholarly journals Effect of Ring Size on Photoisomerization Properties of Stiff Stilbene macrocycles

2019 ◽  
Author(s):  
Sandra Olsson ◽  
Óscar Benito Pérez ◽  
Magnus Blom ◽  
Adolf Gogoll
Keyword(s):  
Dft Calculations ◽  
Dynamic Properties ◽  
Energy Difference ◽  
Carbon Chain ◽  
Experimental Results ◽  
Dft Study ◽  
Ring Size ◽  
Flexible Chain ◽  
Photochemical Properties

A series of stiff stilbene macrocycles have been studied to investigate the possible impact of macrocycle ring size on their photo-dynamic properties. The results show that reducing the ring size counteracts the photoisomerization ability of the macrocycles. However, even the smallest macrocycle studied (stiff stilbene subunits linked by a six carbon chain) showed some degree of isomerization when irradiated. DFT calculations of the energy differences between the E- and Z-isomers show the same trend as the experimental results. Interestingly the DFT study highlights that the energy difference between the E- and Z-isomers of even the largest macrocycle (linked by a twelve carbon chain) is significantly higher than that of the stiff stilbene unit itself. In general, it is indicated that addition of even a flexible chain to the stiff stilbene unit may significantly affect  its photochemical properties and increase the photostability of the resulting macrocycle.

Ring size effect in McMurry cyclization of 1,ω-di((azulen-1-yl)-carbonyl) alkanes

2020 ◽  
Vol 65 (1) ◽  
pp. 83-88
Author(s):  
Eugenia Andreea DRAGU ◽  
◽  
Alexandru C. RAZUS ◽  
Keyword(s):  
Size Effect ◽  
Ring Size
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