Premium
Selective Radical Reactions in Multiphase Systems: Phase‐Transfer Halogenations of Alkanes
Author(s) -
Schreiner Peter R.,
Lauenstein Oliver,
Butova Ekaterina D.,
Gunchenko Pavel A.,
Kolomitsin Igor V.,
Wittkopp Alexander,
Feder Gerald,
Fokin Andrey A.
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20011203)7:23<4996::aid-chem4996>3.0.co;2-p
Subject(s) - chemistry , radical , catalysis , kinetic isotope effect , halogenation , alkane , phase (matter) , limiting , organic chemistry , photochemistry , combinatorial chemistry , computational chemistry , deuterium , mechanical engineering , physics , quantum mechanics , engineering
The present paper shows that selective radical reactions can be initiated and carried out in multiphase systems. This concept is applied to the selective functionalization of unactivated aliphatic hydrocarbons, which may be linear, branched, and (poly)cyclic, strained as well as unstrained. The phase‐transfer system avoids overfunctionalization of the products and simplifies the workup; the selectivities are excellent and the yields are good. This is the only method for direct preparative iodination of alkanes applicable to large scale as well. We demonstrate that the reaction systems are indeed phase‐transfer catalyzed through a systematic study of variations of the reactants, solvents, catalysts, and by measuring as well as computing the H/D kinetic isotope effects for the rate‐limiting C−H abstraction step by . CHal 3 radicals which are held responsible for the observed radical reactions. In the case of . CBr 3 , this key intermediate could also be trapped under otherwise very similar reaction conditions. To stimulate further work, the tolerance of some functional groups was tested as well.