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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 34, Number 8
BKCSDE 34(8)
August 20, 2013 

 
Title
Relative Reactivity of Various Al-substituted-dialkylalans in Reduction of Carbonyl Compounds; A Theoretical Study on Substituent Effect
Author
Keepyung Nahm*, Jin Soon Cha
Keywords
Al-substituted-dialkylalan, MPV reduction, Relative reactivity, DFT, TS barrier
Abstract
Relative reactivity of various Al-substituted dialkylalans (AlR2(X)) in reduction of acetone has been studied with density functional theory and MP2 method. Formation of the alan dimers and the alan-acetone adduct, and the transition state for the Meerwein-Ponndorf-Verley (MPV) type reduction of the adduct were calculated to figure out the energy profile. Formation of dimeric alans is highly exothermic. Both the relative free energies for acetone-alan adduct formation and the TS barriers for the MPV type reduction with respect to alan dimers and acetone were calculated and they show the same trend. Based on these energetic data, relative reactivity of alans is expected to be; AlR2(Cl) > AlR2(OTf) > AlR2(O2CCF3) > AlR2(F) > AlR2(OMs) > AlR2(OAc) > AlR2(OMe) > AlR2(NMe2). The energy profile is relatively well correlated with the experimental order of the reactivity of Al-substituted dialkylalans. It is noted that the substituents of alans have initial effects on the relative free energies for the carbonyl-adduct formation. Therefore, an AlR2(X) which forms a more stable carbonyl-adduct is more reactive in carbonyl reduction.
Page
2335 - 2339
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