Geminal acylation via pinacol rearrangement. Synthesis of spiro[4.n] ring systems

1977 ◽  
Vol 99 (3) ◽  
pp. 961-963 ◽  
Author(s):  
Eiichi Nakamura ◽  
Isao Kuwajima
Keyword(s):  
Ring Systems ◽  
Pinacol Rearrangement ◽  
Geminal Acylation

Synthesis of tricyclo[7.2.1.09,10]dodecan-11-one core ring systems of norditerpenoid alkaloids and racemulosine

2020 ◽  
Vol 7 (7) ◽  
pp. 933-937 ◽  
Author(s):  
Su-Yan Cao ◽  
Hui-Jie Yue ◽  
Meng-Qian Zhu ◽  
Liang Xu
Keyword(s):  
Ring Systems ◽  
Norditerpenoid Alkaloids ◽  
Synthetic Strategy ◽  
Pinacol Rearrangement

A synthetic strategy involving [2 + 2] enyne cycloaddition and pinacol rearrangement to construct common BCD ring systems of norditerpenoid alkaloids and racemulosine was developed.

Geminal acylation of α-heterosubstituted cyclohexanones and their ketals

2010 ◽  
Vol 88 (11) ◽  
pp. 1118-1124 ◽  
Author(s):  
Ian R. Pottie ◽  
Sheldon N. Crane ◽  
Anna Lee Gosse ◽  
David O. Miller ◽  
D. Jean Burnell
Keyword(s):  
Significant Extent ◽  
Amberlyst 15 ◽  
Pinacol Rearrangement ◽  
Diastereomeric Mixture ◽  
Derivatives Of ◽  
Geminal Acylation

Geminal acylation of derivatives of cyclohexanone with Br, Cl, F, and OCH3 in the α position, and of their corresponding dimethyl ketals, could not be accomplished to a significant extent following published procedures. The transformation was accomplished in two steps. The initial BF3·Et2O-mediated reaction with 1,2-bis(trimethylsilyloxy)cyclobutene gave a cyclobutanone product as a mixture of diastereomers. Only with 2-chlorocyclohexanone did this occur with good diastereoselectivity. Then, pinacol rearrangement of the diastereomeric mixture mediated by Amberlyst-15 in benzene provided the heterosubstituted spirocyclic diketone.

Comments on collision mechanics in ring systems

1984 ◽  
Vol 75 ◽  
pp. 407-422
Author(s):  
William K. Hartmann
Keyword(s):  
Asteroid Belt ◽  
Surface Erosion ◽  
Surface Layers ◽  
Ring Systems ◽  
Eclipse Observations ◽  
Saturn’S Rings ◽  
Saturn's Rings

ABSTRACTThe nature of collisions within ring systems is reviewed with emphasis on Saturn's rings. The particles may have coherent icy cores and less coherent granular or frosty surface layers, consistent with thermal eclipse observations. Present-day collisions of such ring particles do not cause catastrophic fragmentation of the particles, although some minor surface erosion and reaccretion is possible. Evolution by collisional fragmentation is thus not as important as in the asteroid belt.

Stochasting modeling of planetary ring systems

1984 ◽  
Vol 75 ◽  
pp. 461-469 ◽  
Author(s):  
Robert W. Hart
Keyword(s):  
Maximum Entropy ◽  
Ring System ◽  
The Sun ◽  
Ultimate State ◽  
Interparticle Interactions ◽  
Ring Systems ◽  
First Order ◽  
Planetary Ring ◽  
Insight Into

ABSTRACTThis paper models maximum entropy configurations of idealized gravitational ring systems. Such configurations are of interest because systems generally evolve toward an ultimate state of maximum randomness. For simplicity, attention is confined to ultimate states for which interparticle interactions are no longer of first order importance. The planets, in their orbits about the sun, are one example of such a ring system. The extent to which the present approximation yields insight into ring systems such as Saturn's is explored briefly.

Diverse Cyclopentenes via Enantioselective Cu-Catalyzed Desymmetrization

2018 ◽  
Author(s):  
Reece Jacques ◽  
Robert D. C. Pullin ◽  
Stephen P. Fletcher
Keyword(s):  
Ring Systems ◽  
Quaternary Centers ◽  
Stereogenic Centers

<div> <div> <div> <p>A highly regio-, diastereo- and enantioselective Cu-catalyzed desymmetrization of diverse meso-bisphosphates with alkyl zirconium nucleophiles has been developed. The reaction allows access to a broad range of functionalized cyclopentenes with up to three contiguous stereogenic centers, including quaternary centers and spirocyclic ring systems.</p></div></div></div>

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