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Photoacetylation of Diamondoids: Selectivities and Mechanism
Author(s) -
Fokin Andrey A.,
Gunchenko Pavel A.,
Novikovsky Anatoliy A.,
Shubina Tatyana E.,
Chernyaev Boris V.,
Dahl Jeremy E. P.,
Carlson Robert M. K.,
Yurchenko Alexander G.,
Schreiner Peter R.
Publication year - 2009
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200900600
Subject(s) - chemistry , electrophile , steric effects , diamondoid , computational chemistry , diradical , kinetic isotope effect , electrophilic substitution , intramolecular force , substitution reaction , allylic rearrangement , radical , photochemistry , medicinal chemistry , stereochemistry , deuterium , organic chemistry , molecule , catalysis , excited state , physics , quantum mechanics , nuclear physics , singlet state
The photoacetylation of diamondoids (nanodiamonds), in particular [1212]pentamantane, [1(2,3)4]pentamantane, and [123]tetramantane, with diacetyl almost exclusively gives apical acetyl derivatives. The mechanism of the photoacetylation was studied on the basis of a comparative analysis of the experimental deuterium kinetic isotope effects as well as the observed C–H bond substitution selectivities, which were also computed at the B3LYP, B3PW91, and MP2 levels of theory including polarized continuum modeling of solvent effects. The high apical C–H bond selectivities in the photoacetylation of diamondoids are determined by the higher polarizabilities of the cages along the apical direction in the transition structures for hydrogen abstraction with the triplet diacetyl diradical. Steric effects play only a minor role, and in combination with solvation, outweigh charge‐transfer effects that usually favor medial substitution with electrophiles and electrophilic radicals.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)