Organoborierung von Alkinylstannanen, XI [1] Synthese von substituierten Alkenen ausgehend von 9-Borabicyclo [3.3.1] nonan-Derivaten / Organoboration of Alkynylstannanes, XI [1] Synthesis of Substituted Alkenes from 9-Borabicyclo[3,3,l]nonane Derivatives

1981 ◽  
Vol 36 (10) ◽  
pp. 1265-1269 ◽  
Author(s):  
Christoph Bihlmayer ◽  
Bernd Wrackmeyer
Keyword(s):  
Nmr Spectra ◽  
Thermodynamic Control ◽  
Type Intermediate

Abstract Organoboration, 9-Borabicyclo[3.3.1]nonanes, NMR Spectra New alkene derivatives are obtained from the reaction between 9-ethyl-borabicyclo-[3.3.1]nonane and alkynyl stannanes under kinetic or thermodynamic control. NMR evidence for a borate type intermediate is presented.

On the construction of the C/D ring systems of chasmanine and napelline by diene addition

1978 ◽  
Vol 56 (8) ◽  
pp. 1102-1113 ◽  
Author(s):  
Karnail S. Atwal ◽  
Rinaldo Marini-Bettolo ◽  
Ignacio H. Sanchez ◽  
Thomas Y. R. Tsai ◽  
Karel Wiesner
Keyword(s):  
Nmr Spectra ◽  
Model Compound ◽  
Present Model ◽  
Ring System ◽  
High Yield ◽  
Total Syntheses ◽  
Model Studies ◽  
Order Of Magnitude ◽  
Photochemical Route ◽  
Type Intermediate

The construction of the C/D ring system of the alkaloids chasmanine and napelline by modification and rearrangement of a common intermediate is explored on model compounds.The phenolic acid 9 was oxidized to the spirolactone 10. Addition of benzyl vinyl ether to this material gave the adduct 28 in high yield. This central 'nordenudatine' type intermediate was then modified (in a very few stereospecific steps) to the 'napelline' model compound 47 and to the keto acetal 38. Compound 38 is an intermediate of our photochemical route and we have already described its conversion to a chasmanine model derivative.The new syntheses of chasmanine and napelline foreshadowed by the present model studies are expected to be completely stereo- and regiospecific, almost 10 steps shorter and an order of magnitude more efficient than the total syntheses of these two alkaloids which we have reported in the recent past.Incidentally, with these model studies, the methoxy ketone 20 was prepared. The methoxyl in this compound is epimeric to the corresponding (C16) methoxyl of the aconite alkaloids. Some relevant observations on the nmr spectra and allylic rearrangement (pyro–isopyro rearrangement) of this material are also reported.

NMR spectra and relaxation in incommensurate systems in the presence of a devil's staircase

1985 ◽  
Vol 46 (7) ◽  
pp. 1205-1209 ◽  
Author(s):  
R. Blinc ◽  
S. Žumer ◽  
D.C. Ailion ◽  
J. Nicponski
Keyword(s):  
Nmr Spectra ◽  
Devil's Staircase ◽  
Devil’S Staircase

Stereodivergent Alkyne Hydrofluorination Using a Simple Practical Reagent

2020 ◽  
Author(s):  
Rui Guo ◽  
Xiaotian Qi ◽  
Hengye Xiang ◽  
Paul Geaneoates ◽  
Ruihan Wang ◽  
...  
Keyword(s):  
Bond Formation ◽  
Biologically Active ◽  
Dft Studies ◽  
Thermodynamic Control ◽  
Important Goal ◽  
Peptide Bonds ◽  
Metal Free ◽  
Vinyl Cation ◽  
E And Z Isomers ◽  
Vinyl Fluorides

Vinyl fluorides play an important role in drug development as they serve as bioisosteres for peptide bonds and are found in a range of biologically active molecules. The discovery of safe, general and practical procedures to prepare vinyl fluorides remains an important goal and challenge for synthetic chemistry. Here we introduce an inexpensive and easily-handled reagent and report simple, scalable, and metal-free protocols for the regioselective and stereodivergent hydrofluorination of alkynes to access both the E and Z isomers of vinyl fluorides. These conditions were suitable for a diverse collection of alkynes, including several highly-functionalized pharmaceutical derivatives. Mechanistic and DFT studies support C–F bond formation through a vinyl cation intermediate, with the (E)- and (Z)-hydrofluorination products forming under kinetic and thermodynamic control, respectively.<br>

Some Considerations Regarding the 1H and 13C Spectra of 4-(1-azulenyl)-2,6-bis(2-heteroaryl-vinyl)- pyrylium and Pyridinium and their Corresponding Pyridines

2018 ◽  
Vol 69 (1) ◽  
pp. 64-69
Author(s):  
Liviu Birzan ◽  
Mihaela Cristea ◽  
Constantin C. Draghici ◽  
Alexandru C. Razus
Keyword(s):  
Double Bond ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Pyridinium Salts ◽  
13C Nmr Spectra ◽  
1H And 13C Nmr ◽  
Pyrylium Salts

The 1H and 13C NMR spectra of several 2,6-diheteroarylvinyl heterocycles containing 4-azulenyl moiety were recorded and their proton and carbon chemical shifts were compared with those of the compounds without double bond between the heterocycles. The influence of the nature of central and side heterocycles, molecule polarization and anisotropic effects were revealed. The highest chemical shifts were recorded for the pyrylium salts and the lowest at pyridines, but in the case of the pyridinium salts, the protons chemical shifts at the central heterocycle are more shielded due to a peculiar anisotropy of the attached vinyl groups.

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