ISSN:
0947-3440
Keywords:
Tetradehydrodianthracene
;
Diels-Alder reactions
;
Cycloadditions
;
Tetrazines
;
Steric hindrance
;
Kinetics
;
Semiempirical calculations
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Theoretical calculations and simple MO considerations predict that a coplanar and spatially close arrangement of double bonds in structures such as tetradehydrodianthracene 1, should both lower the LUMO and raise the HOMO energy of the π system. Thus the reactivity in Diels-Alder reactions towards electron-rich, as well as electron-deficient, dienes should be enhanced. The first effect has already been shown in a previous paper, the latter statement is now also confirmed by the reactivity of 1 in Diels-Alder reactions with inverse electron demand. In [4 + 2] cycloaddition reactions of 1 with 1,2,4,5-tetrazines 2 the electronic effect of 3,6 substituents in tetrazines is far outweighed by steric factors resulting in an unexpected reactivity sequence: 2a ≫ 2b ≈ 2c 〉 2d.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.199719970726
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