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Reactivity and Selectivity of Organotin Reagents in Allylation and Arylation: Nucleophilicity Parameter as a Guide

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journal contribution
posted on 27.06.2011, 00:00 by Sanjay Pratihar, Sujit Roy
By using the inverse concept of electrophilicity and nucleophilicity and with two different available equations from the literature for electrodonating power, the global nucleophilicity index (N) of 99 organotin and 10 allylmetal reagents (metal = Mg, Zn, B, In, Si) have been calculated at the B3LYP/LAN2DZ, 6-31G(d) level of theory. The nucleophilicity scale is validated by the good linear fit between N-values of para-substituted arylstannanes and Hammett σp values of the substituents on the aryl ring. The global nucleophilicity index N has been utilized successfully to explain the reactivity of aryltin and allyltin reagents, to understand the effect of substituents directly attached to tin and those attached on the transferable group, and to rationalize the effect of solvents on reactivities of organotin reagents. The local nucleophilicity index value (Nk-) proved to be a useful local descriptor. The Nk- values at the α- and γ-position in various allylmetal reagents (metal = Mg, Sn, Zn, In, B, Si) have been calculated. Aided by local nucleophilicity values, the regioselectivity in carbonyl allylation (in the presence and in the absence of Lewis or Brǿnstead acid) has been analyzed.