posted on 2015-12-17, 04:46authored byKumar
Dilip Ashtekar, Nastaran Salehi Marzijarani, Arvind Jaganathan, Daniel Holmes, James E. Jackson, Babak Borhan
We
introduce a previously unexplored parameterhalenium
affinity (HalA)– as a quantitative descriptor
of the bond strengths of various functional groups to halenium ions.
The HalA scale ranks potential halenium ion acceptors
based on their ability to stabilize a “free halenium ion”.
Alkenes in particular but other Lewis bases as well, such as amines,
amides, carbonyls, and ether oxygen atoms, etc., have been classified
on the HalA scale. This indirect approach enables
a rapid and straightforward prediction of chemoselectivity for systems
involved in halofunctionalization reactions that have multiple nucleophilic
sites. The influences of subtle electronic and steric variations,
as well as the less predictable anchimeric and stereoelectronic effects,
are intrinsically accounted for by HalA computations,
providing quantitative assessments beyond simple “chemical
intuition”. This combined theoretical–experimental approach
offers an expeditious means of predicting and identifying unprecedented
reactions.