5-Endo-dig radical cyclizations: "The poor cousins" of the radical cyclizations family

Journal of the American Chemical Society

Volumn 127, Issue 26, 2005, Pages 9534-9545

  Alabugin, Igor V ^a   Manoharan, Mariappan ^a  

^a FLORIDA STATE UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ACTIVATION ENERGY; CHEMICAL BONDS; CONSTRAINT THEORY; FREE RADICALS; THERMODYNAMIC PROPERTIES;

MARCUS THEORY; RADICAL CYCLIZATION; REORIENTATION; STRAIN EFFECT;

ORGANIC COMPOUNDS;

ACETYLENE;

ARTICLE; CHEMICAL ANALYSIS; CHEMICAL BOND; CHEMICAL REACTION; CYCLIZATION; DENSITY FUNCTIONAL THEORY; ELECTRON TRANSPORT; EQUILIBRIUM CONSTANT; GEOMETRY; MOLECULAR STABILITY; RADICAL CYCLIZATION; REACTION ANALYSIS; SUBSTITUTION REACTION; THERMODYNAMICS;

EID: 21744442964     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja050976h     Document Type: Article

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164. .) interaction is only 0.4 kcal/mol in the product. This observation is not surprising and can be explained by unfavorable hybridization of the in-plane S lone pair having little p-character (ca. 35%) in contrast to the respective O-lone pair (ca. >60%). Alabugin, I. V.; Manoharan, M.; Zeidan, T. A. J. Am. Chem. Soc. 2003, 125, 14014.
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179. We will discuss only the 5-endo cyclizations below. The other details of the mechanism will be discussed elsewhere.
180. The transoid conformer of the radical 88 is only 0.1 kcal/mol lower in energy than the cisoid radical.
181. Additionally, the reactivity of Si-centered radicals and C-centered radicals toward H-abstraction should be different.
182. This is an interesting observation because cyclizations of Si-centered radicals should be in general less exothermic than those of C-centered radicals because C-Si bonds are weaker than C-C bonds.