Unsaturated macrocyclic compounds. LXVII. Synthesis of the 1-methoxy-2,8,10-tridehydro[17]annulenyl anion, and aromatic 17-membered ring cyclic system

1969 ◽  
Vol 91 (26) ◽  
pp. 7518-7520 ◽  
Author(s):  
John Griffiths ◽  
Franz Sondheimer
Keyword(s):  
Membered Ring ◽  
Macrocyclic Compounds ◽  
Cyclic System

Oxidation and epoxidation of 4,4-dimethyl-A-homo-5-cholesten-4a-ols

1985 ◽  
Vol 50 (1) ◽  
pp. 114-131 ◽  
Author(s):  
Helena Velgová ◽  
Jaroslav Zajíček
Keyword(s):  
Double Bond ◽  
Membered Ring ◽  
Allylic Alcohols ◽  
Cyclic System ◽  
H Nmr ◽  
Nmr Data ◽  
Epoxidation Of Olefins

Oxidation of four stereoisomeric 3-acetoxy-4,4-dimethyl-A-homo-5-cholesten-4a-ols I-IV with Sarett's and Jones's reagent was investigated. 4αβ-Hydroxy derivatives II and IV afforded corresponding enones V and XVI as the main products, while in the case of 4aα-hydroxy derivatives I and III the formation of 5β,6β-epoxides was observed both in the oxidation according to Jones and in the oxidation with the Sarett's reagent. The study of the stereochemistry of epoxidation of olefins I-IV and their derivatives showed that the epoxidation of the 5,6-double bond takes place preferentially from the β-side of the cyclic system. On the basis of 1H NMR data the preferred conformation of the seven-membered ring A in the allylic alcohols I-IV was determined; on its basis the effects leading to different behaviour of epimers I, III and II, IV during oxidation are discussed.

scholarly journals Crystal structure and Hirshfeld surface analysis of dimethyl (1R*,3aS*,3a1 R*,6aS*,9R*,9aS*)-3a1,5,6,9a-tetrahydro-1H,4H,9H-1,3a:6a,9-diepoxyphenalene-2,3-dicarboxylate

2019 ◽  
Vol 75 (4) ◽  
pp. 460-464
Author(s):  
Kseniia A. Alekseeva ◽  
Pavel V. Raspertov ◽  
Sevim Türktekin Çelikesir ◽  
Mehmet Akkurt ◽  
Flavien A. A. Toze ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Surface Analysis ◽  
Chair Conformation ◽  
Membered Ring ◽  
Hirshfeld Surface ◽  
Hirshfeld Surface Analysis ◽  
Cyclic System ◽  
Axis Direction ◽  
Carboxylate Groups

The title diepoxyphenalene derivative, C17H18O6, comprises a fused cyclic system containing four five-membered rings (two dihydrofuran and two tetrahydrofuran) and one six-membered ring (cyclohexane). The five-membered dihydrofuran and tetrahydrofuran rings adopt envelope conformations, and the six-membered cyclohexane ring adopts a distorted chair conformation. Two methyl carboxylate groups occupy adjacent positions (2- and 3-) on a tetrahydrofuran ring. In the crystal, two pairs of C—H...O hydrogen bonds link the molecules to form inversion dimers, enclosing two R 2 2(6) ring motifs, that stack along the a-axis direction and are arranged in layers parallel to the bc plane.

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

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