Novel concise ring closure leading to bridged ten-membered ring compounds

1999 ◽  
pp. 893-894 ◽  
Author(s):  
Hiroshi Fujishima ◽  
Hiroshi Takeshita ◽  
Masahiro Toyota ◽  
Masataka Ihara
Keyword(s):  
Membered Ring ◽  
Ring Closure ◽  
Ring Compounds

ChemInform Abstract: Novel Concise Ring Closure Leading to Bridged Ten-Membered Ring Compounds.

ChemInform ◽  
2010 ◽  
Vol 30 (37) ◽  
pp. no-no
Author(s):  
Hiroshi Fujishima ◽  
Hiroshi Takeshita ◽  
Masahiro Toyota ◽  
Masataka Ihara
Keyword(s):  
Membered Ring ◽  
Ring Closure ◽  
Ring Compounds

scholarly journals Catalytic Synthesis of 8-Membered Ring Compounds via Cobalt(III)-Carbene Radicals

2020 ◽  
Author(s):  
M. Zhou ◽  
J.I. van der Vlugt ◽  
Bas de Bruin
Keyword(s):  
Dft Calculations ◽  
Hydrogen Atom Transfer ◽  
Membered Ring ◽  
Ring Closure ◽  
Radical Intermediates ◽  
Aryl Aldehydes ◽  
Ring Compounds ◽  
Ring Structures ◽  
Radical Type ◽  
Powerful Strategy

The metalloradical activation of o-aryl aldehydes with cobalt(II) porphyrin complexes as catalysts produces cobalt(III)-carbene radical intermediates, providing a novel and powerful strategy for the synthesis of medium-sized ring structures. Herein we make use of the intrinsic radical-type reactivity of cobalt(III)-carbene radical intermediates in the [Co<sup>II</sup>(TPP)]-catalyzed (TPP = tetraphenylporphyrin) synthesis of two types of 8 membered ring compounds; novel dibenzocyclooctenes and unique monobenzo-cyclooctadienes. The method was successfully applied to a variety of substrates, producing several 8-membered ring compounds in good yields and with excellent substituent tolerance. DFT calculations and experimental results suggest that the reactions proceed via initial hydrogen atom transfer from the bis-allylic/benzallylic C-H bond to the carbene radical moiety, followed by two divergent processes for ring-closure to the two different types of 8-membered ring products. While the dibenzocyclooctenes are formed by dissociation of o quinodimethanes (o-QDMs) from the catalyst that undergo an uncatalyzed ring-closure reaction involving 8-pi-cyclisation, DFT calculations suggest that ring-closure to the monobenzocyclooctadienes involves a radical-rebound step in the coordination sphere of cobalt. The latter mechanism implies that unprecedented enantioselective ring-closure reactions to chiral benzocyclooctadienes should be possible, as was confirmed for reactions mediated by a chiral cobalt-porphyrin catalyst.

scholarly journals Synthese und Cyclisierung von Boryl- und Silylhydrazonen / Synthesis and Cyclisation of Boryl- and Silylhydrazones

2010 ◽  
Vol 65 (5) ◽  
pp. 587-602 ◽  
Author(s):  
Martin Görth ◽  
Ute Schneider ◽  
Holger Ott ◽  
Carola Schulzke ◽  
Dietmar Stalke ◽  
...  
Keyword(s):  
Main Product ◽  
Lithium Salt ◽  
Membered Ring ◽  
Molecular Structures ◽  
Ring Closure ◽  
Molar Ratio ◽  
Lithium Salts ◽  
Substitution Reactions ◽  
Ring Compounds ◽  
Methylene Group

Reactions of the lithium salts of the tert-butylmethylhydrazones Me3C(Me)C=N-NLiR, (R = H, Me, CMe3) with fluorosilanes and -boranes in a molar ratio 1 : 1 gave the silyl- (1 - 3, 5, 6) and borylhydrazones (4, 8) Me3 C(Me)C=N-N(R)Rʹ; 1: R = H, Rʹ = SiFMe2 ; 2: R = H, Rʹ = SiMe2CMe3; 3: R = H, Rʹ = SiF(CMe3 )2; 4: R = H, Rʹ = BFN(SiMe3)2; 5: R = Me3 C, Rʹ = SiF2CMe3; 6: R = Me3C, Rʹ = F2SiC(SiMe3)3; 8: R = Me3C, Rʹ = BFN(SiMe3)2. The lithiated hydrazone Me2C=N-NH(Me) reacted with F3SiC(SiMe3)3 to give the silylhydrazone Me2C=N- NHSiF2C(SiMe3)3, 7. Because of the fluoro functionality of 1 and 4, the bis-hydrazonylsilane 9 and the bis- and tris-hydrazonylboranes 10 and 11 could be synthesised, (Me3C(Me)C=N-NH)2R; 9: R = SiMe2 , 10: R = BN(SiMe3)2; 11: (Me3C(Me)C=N-NH)3B. Starting from 2 and its lithium salt, secondary substitutions are possible. Bis(silyl)- and silyl(boryl)hydrazones are formed (12 - 15); Me3C(Me)C=N(R) (SiMe2CMe3) 12: R = SiFMe2; 13: R = SiF(CMe3)2; 14: R = SiF2CMe3; 15: R = BFN(SiMe3 )2. Ring closure occurs in the reaction of dilithiated Me2C=N- NHCMe3 with F2Si(CHMe2)2. The 1,2-diaza-3-sila-5-cyclopentene 16 is isolated. The fluorofunctional silyl-hydrazones 7, 12, and 13 cyclise in reactions with t-BuLi to give 1,2-diaza-3-sila-5- cyclopentenes 17 - 20; RN(N=CRʹ-CH2)Rʺ; 17: R =Me,Rʹ = Me3C, Rʺ = SiFC(SiMe3)3; 18: R = Me3C, Rʹ = SiMe2CMe3, Rʺ = SiMe2; 19: R =Me3C, Rʹ = SiMe2CMe3, Rʺ = Si(CMe3)2. A 1,2- diaza-3-bora-5-cyclopentene 20 is the result of the reaction of 8 with t-BuLi: Me3CN(N=CCMe3- CH2)BN(SiMe3)2. The H-acidic methylene group of the five-membered ring in 20 can be lithiated with n-BuLi and substituted with fluorosilanes. Starting from 16 and 20, the silyl-substituted rings Me3CN(N=CMe-CHR)Si(CHMe2)2 21 - 23 and 25 are obtained; 21: R = SiMe3; 22: R = SiF2C(SiMe3)3; 23: R = SiF3; 25: Me3CN[N=CC(Me)3CHSiMe3]BN(SiMe3)2. Using SiF4 as fluorosilane, the main product is the difluorosilane containing two rings; F2Si[CHC(Me)=N-NCMe3- Si(CHMe2)2]2. The methine group in 4-position of the silyl-substituted rings is also acidic and reacts with n-BuLi to give lithium salts which react with aminodifluoroboranes giving the ring compounds Me3CN[N=C(CMe3)C(SiMe2R)(FBNRʹ SiMe3)]SiMe2 26 - 28; 26: R = Me, Rʹ = CMe3; 27: R = F, Rʹ = CMe3 ; 28: R = F, Rʹ = SiMe3. In contrast to the substitution reactions of fluorosilanes with lithiated rings, an unusual oxidation reaction occurs starting from lithiated Me3CN(N=C(CMe3)CH2)Si(CHMe2)2 and ClSiMe2CMe3 to give 29, in which a C-C bond in 4- position links two five-membered rings. The disilane (Me3CSiMe2)2 is formed as a by-product of this reaction. The combination of the N-SiF2CMe3-substituted hydrazones 5 and 14 with t-BuLi in a molar ratio 1 : 2 leads to the colourless, crystalline tricyclic products 30 and 31 which are dimeric 1,2-diaza-3-sila-3,5-cyclopentadienes. The molecular structures of 3, 6, 11, 30, and 31 are reported.

scholarly journals Catalytic Synthesis of 8-Membered Ring Compounds via Cobalt(III)-Carbene Radicals

2020 ◽  
Author(s):  
M. Zhou ◽  
J.I. van der Vlugt ◽  
Bas de Bruin
Keyword(s):  
Dft Calculations ◽  
Hydrogen Atom Transfer ◽  
Membered Ring ◽  
Ring Closure ◽  
Radical Intermediates ◽  
Aryl Aldehydes ◽  
Ring Compounds ◽  
Ring Structures ◽  
Radical Type ◽  
Powerful Strategy

The metalloradical activation of o-aryl aldehydes with cobalt(II) porphyrin complexes as catalysts produces cobalt(III)-carbene radical intermediates, providing a novel and powerful strategy for the synthesis of medium-sized ring structures. Herein we make use of the intrinsic radical-type reactivity of cobalt(III)-carbene radical intermediates in the [Co<sup>II</sup>(TPP)]-catalyzed (TPP = tetraphenylporphyrin) synthesis of two types of 8 membered ring compounds; novel dibenzocyclooctenes and unique monobenzo-cyclooctadienes. The method was successfully applied to a variety of substrates, producing several 8-membered ring compounds in good yields and with excellent substituent tolerance. DFT calculations and experimental results suggest that the reactions proceed via initial hydrogen atom transfer from the bis-allylic/benzallylic C-H bond to the carbene radical moiety, followed by two divergent processes for ring-closure to the two different types of 8-membered ring products. While the dibenzocyclooctenes are formed by dissociation of o quinodimethanes (o-QDMs) from the catalyst that undergo an uncatalyzed ring-closure reaction involving 8-pi-cyclisation, DFT calculations suggest that ring-closure to the monobenzocyclooctadienes involves a radical-rebound step in the coordination sphere of cobalt. The latter mechanism implies that unprecedented enantioselective ring-closure reactions to chiral benzocyclooctadienes should be possible, as was confirmed for reactions mediated by a chiral cobalt-porphyrin catalyst.

Isomerization of the Isoprene Hydroxy Nitrates and Formation of Orthonitrite Compounds

2019 ◽  
Author(s):  
Gabriel da Silva
Keyword(s):  
Hydroxy Group ◽  
Peroxyl Radical ◽  
Branching Fractions ◽  
Membered Ring ◽  
Low Energy ◽  
Peroxyl Radicals ◽  
Aerosol Formation ◽  
Subsequent Removal ◽  
Ring Compounds ◽  
Group Migration

Atmospheric oxidation of isoprene produces significant yields of eight unique nitrate 11 compounds, each with a β- or δ-hydroxy group. These isoprene hydroxy nitrates (ISOPNs) 12 significantly impact upon global NOx budgets, O3 levels, and aerosol formation. 13 Uncertainties exist, however, in our understanding of ISOPN chemistry, particularly in their 14 yields from the reaction of isoprene peroxyl radicals with NO. This study describes novel 15 isomerization reactions of the ISOPNs, identified through the application of computational 16 chemistry techniques. These reactions produce saturated polycyclic orthonitrite compounds 17 via attack of the R–NO2 group on the vinyl moiety. For the δ-hydroxy nitrates, low-energy 18 isomerization pathways exist to six-membered ring compounds that are around 5 kcal mol-1 19 exothermic. These reactions proceed with barriers around 15 kcal mol-1 below the 20 respective peroxyl radical + NO reactants and yield orthonitrites that can further isomerize 21 to β-hydroxy ISOPNs. Moreover, the δ-hydroxy nitrates can directly interconvert with their β 22 substituted counterparts via NO3 group migration, with barriers that are lower yet. It follows 23 that β-hydroxy nitrates may be stabilized in the δ-hydroxy form, and vice versa. Moreover, 24 the lowest-energy pathway for dissociation of the δ-hydroxy ISOPNs is for the formation of 25 β-hydroxy alkoxyl radicals, and because of this established branching fractions between the 26 various isoprene peroxyl radicals may require re-evaluation. The results presented here also 27 suggest that ISOPNs may be stabilized to some extent in their saturated orthonitrite forms, 28 which has implications for both the total nitrate yield and for their subsequent removal by 29 OH, O3, and photolysis.<br><br>

scholarly journals Low-valent dialkoxytitanium(ii): a useful tool for the synthesis of functionalized seven-membered ring compounds

2021 ◽  
Vol 57 (29) ◽  
pp. 3603-3606
Author(s):  
Florent Bodinier ◽  
Youssouf Sanogo ◽  
Janick Ardisson ◽  
Marie-Isabelle Lannou ◽  
Geoffroy Sorin
Keyword(s):  
Grignard Reagent ◽  
Membered Ring ◽  
Ring Compounds ◽  
Low Valent

Herein, we describe unprecedented access to all-carbon or heterocyclic seven-membered ring frameworks from 1,8-ene-ynes promoted by inexpensive low-valent titanium(ii) species, readily available from a combination of Ti(OiPr)4 and Grignard reagent.

Enantioselective Functionalization of Prochiral Cyclobutanones and Cyclobutenones

Synlett ◽  
2021 ◽  
Author(s):  
Memg Wang ◽  
Changxu Zhong ◽  
Ping Lu
Keyword(s):  
Asymmetric Synthesis ◽  
Membered Ring ◽  
Enantioselective Synthesis ◽  
Ring Compounds ◽  
Recent Advances ◽  
Cyclobutane Derivatives

Enantioselective synthesis of cyclobutane derivatives is still a challenging topic in asymmetric synthesis. [2+2]-Cycloaddition and skeleton rearrangement are two primary strategies to this end. Recently, functionalization of cyclobutanones and cyclobutenones, which are readily available via [2+2]-cycloadditions as prochiral substrates, has emerged as a powerful tool to access versatile four-membered ring compounds. Herein, we summarize some recent advances in these areas from our and other groups.

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