Barrier to 1,3-sigmatropic shift in odd electron ions. A MINDO/3 study of H, OH, CH3 and C6H5 migration

1982 ◽  
Vol 17 (10) ◽  
pp. 534-536 ◽  
Author(s):  
Y. Hoppilliard ◽  
G. Bouchoux
Keyword(s):  
Sigmatropic Shift

C−N Bond Insertion of a Complexed Phosphinidene into a Bis(imine) − A Novel 2,3-Sigmatropic Shift

2002 ◽  
Vol 2002 (11) ◽  
pp. 1797-1802 ◽  
Author(s):  
Mark J. M. Vlaar ◽  
Pieter Valkier ◽  
Marius Schakel ◽  
Andreas W. Ehlers ◽  
Martin Lutz ◽  
...  
Keyword(s):  
Sigmatropic Shift

Anionic rearrangement of 7-norbornadienol: a 1,3-sigmatropic shift

1976 ◽  
Vol 98 (5) ◽  
pp. 1241-1247 ◽  
Author(s):  
Boris Franzus ◽  
Monte L. Scheinbaum ◽  
Deborah L. Waters ◽  
Harold B. Bowlin
Keyword(s):  
Sigmatropic Shift

Why Buy That Theory?

2012 ◽  
Author(s):  
Roald Hoffmann
Keyword(s):  
Scientific Community ◽  
Physical Phenomenon ◽  
Platonic Solid ◽  
Orbital Symmetry ◽  
Theory Of Evolution ◽  
Simple Theories ◽  
Sigmatropic Shift ◽  
The World ◽  
One Step ◽  
Synthetic Chemist

The theory of theories goes like this: A theory will be accepted by a scientific community if it explains better (or more of) what is known, fits at its fringes with what is known in other parts of our universe, and makes verifiable, preferably risky, predictions. Sometimes it does go like that. So the theory that made my name (and added to the already recognized greatness of the man with whom I collaborated, the synthetic chemist of the 20th century, R. B. Woodward) did make sense of many disparate and puzzling observations in organic chemistry. And “orbital symmetry control,” as our complex of ideas came to be called, made some risky predictions. I remember well the day that Jerry Berson sent us his remarkable experimental results on the stereochemistry of the so- called 1,3-sigmatropic shift . It should proceed in a certain way, he reasoned from our theory—a non-intuitive way. And it did. But much that goes into the acceptance of theories has little to do with rationalization and prediction. Instead, I will claim, what matters is a heady mix of factors in which psychological attitudes figure prominently. A simple equation describing a physical phenomenon (better still, many), the molecule shaped like a Platonic solid with regular geometry, the simple mechanism (A→B, in one step)—these have tremendous aesthetic appeal, a direct beeline into our soul. They are beautifully simple, and simply beautiful. Theories of this type are awesome in the original sense of the word—who would deny this of the theory of evolution, the Dirac equation or general relativity? A little caution might be suggested from pondering the fact that political ads patently cater to our psychobiological predilection for simplicity. Is the world simple? Or do we just want it to be such? In the dreams of some, the beauty and simplicity of equations becomes a criterion for their truth. Simple theories seem to validate that idol of science, Ockham’s Razor. In preaching the poetic conciseness and generality of orbital explanations, I have succumbed to this, too.

Total Synthesis of (±)-Cassumunins A–C and Curcumin Analogues

Synthesis ◽  
2020 ◽  
Vol 52 (10) ◽  
pp. 1561-1575 ◽  
Author(s):  
Faiz Ahmed Khan ◽  
Mulla Althafh Hussain
Keyword(s):  
Total Synthesis ◽  
Claisen Rearrangement ◽  
Aldol Condensation ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Full Account ◽  
Curcumin Analogues ◽  
Cross Coupling Reaction ◽  
Sigmatropic Shift ◽  
Novel Approaches

A full account of the total synthesis of (±)-cassumunins A–C – superior antioxidants and anti-inflammatory agents – is given. Two novel approaches were developed for synthesizing cassumunins. The total synthesis of cassumunins A and B was accomplished in five linear steps from a known aldehyde in good overall yields of 50 and 43%, respectively, featuring a cascade [3,3]-sigmatropic shift (the Claisen rearrangement) and Heck cross-coupling reaction. Consequently, the total synthesis of cassumunin C was accomplished in three linear steps from a known alcohol with an overall yield of 53%. The key features involved in this synthesis are tandem [3,3]-sigmatropic shift, SN2′ reaction, and aldol condensation. Moreover, a total of eighteen symmetrical and unsymmetrical curcumin analogues were synthesized.

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