Alkynyldicobalt Derivatives of Dibenzosuberenol and Dibenzocyclooctatrien-5-ol: Ring Conformations, Ease of Carbonyl Elimination and Relevance to Pauson-Khand Cyclization

2017 ◽  
Vol 2017 (13) ◽  
pp. 2048-2057
Author(s):  
Sarah A. Brusey ◽  
Wen Shen ◽  
Helge Müller-Bunz ◽  
Yannick Ortin ◽  
Paul Evans ◽  
...  
Keyword(s):  
Derivatives Of ◽  
Ring Conformations

Nuclear magnetic resonance characterization of the ring conformations of monosubstituted derivatives of 1,3-dioxa-5,6-benzocycloheptene

1983 ◽  
Vol 61 (1) ◽  
pp. 109-115 ◽  
Author(s):  
R. St-Amour ◽  
M. St-Jacques
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Substituent Effects ◽  
Steric Effects ◽  
Slow Exchange ◽  
Conformational Properties ◽  
Derivatives Of ◽  
Ring Conformations ◽  
Twist Boat

The conformational properties of 2-alkyl (Me, Et, i-Pr, and t-Bu) and 2-phenyl derivatives of 1,3-dioxa-5,6-benzocycloheptene (1) were studied by 13C dnmr. Analysis of slow exchange spectra at 100.6 MHz indicates that all derivatives except tert-butyl exist in an equilibrium of chair (major) and twist-boat (minor) conformations. Substituent effects on the position of the equilibrium are rationalized in terms of steric effects.

Preparation of E-Secolupane Acids and Lactones

2003 ◽  
Vol 68 (4) ◽  
pp. 751-778 ◽  
Author(s):  
Iva Tišlerová ◽  
Eva Klinotová ◽  
Jiří Klinot ◽  
Jan Sejbal ◽  
Martin Rejzek ◽  
...  
Keyword(s):  
Dicarboxylic Acids ◽  
Epoxide Ring ◽  
Carboxylic Group ◽  
Reaction Conditions ◽  
Dioic Acid ◽  
Hydroxymethyl Group ◽  
Nmr Techniques ◽  
Derivatives Of ◽  
Ring Conformations ◽  
C Nmr

Anhydrides of 3β,28-diacetoxy-21,22-secolup-18-ene-21,22-dioic acid (1) and (19R)-3β,28-diacetoxy-18β,19-epoxy-21,22-secolupane-21,22-dioic acid (11) undergo alkaline hydrolysis yielding the corresponding dicarboxylic acids. Depending on reaction conditions, these acids are further transformed yielding various lactones, liberating C-28 hydroxymethyl group, or undergoing decarboxylation leading to nor derivatives. This method has been used to prepare a diverse series of E-secolupane derivatives including lactonoacids (e.g. 2 and 15), lactones (4, 16 and 17), 28-nor derivatives (3 and 6) and 21,28-dinor derivatives (12 and 13). Derivatives of (19R)-3β,28-dihydroxy-18β,19-epoxy-21,22-secolupane-21,22-dioic acid 21,28-lactone (15c), bearing a free carboxylic group, are labile and can only be isolated as the corresponding dilactones 17. The C-22 carboxylic group forms a β-lactone by a nucleophilic α-directed attack on the C-18 epoxide ring carbon atom resulting in (19R)-3β,19-dihydroxy-21,22-secolupane-21,28:22,18α-dilactone (17b) and related derivatives. The structure and stereochemistry of the compounds discussed in this contribution were derived from IR, MS, 1H and 13C NMR spectra (1D and 2D COSY, TOCSY, NOESY, HSQC, HMBC). Using these NMR techniques and measuring the solvent influence on the IR carbonyl stretching frequencies of the dilactones 17, an equilibrium between the two E-ring conformations was shown to exist.

Physical Properties of TCNQ Salts with N-Methyl Derivatives of Pyridine

1982 ◽  
Vol 85 (1) ◽  
pp. 257-263 ◽  
Author(s):  
A. Graja ◽  
M. Przybylski ◽  
B. Butka ◽  
R. Swietlik
Keyword(s):  
Physical Properties ◽  
Methyl Derivatives ◽  
Derivatives Of

Diorganyl Derivatives of Tellurium(IV) (σ-Telluranes of R 2 TeX 2 Type)

2002 ◽  
Vol 23 (2) ◽  
pp. 125-207 ◽  
Author(s):  
Igor D. Sadekov ◽  
Alexander V. Zakharov ◽  
Alexander A. Maksimenko
Keyword(s):  
Derivatives Of
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