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Nucleophilicities of Triflinate-Stabilized Carbanions

Stefan Berger 1Herbert Mayr 2

1. Ludwig Maximilians Universitaet, Department of Pharmacy (LMU), Butenandtstr. 5-13, Munich 81377, Germany
2. LMU München, Department Chemie und Biochemie, Butenandtstrasse 5-13, München 81377, Germany


The trifluoromethylsulfonyl group is known to be one of the strongest electron accepting groups. Systematic investigations by Terrier and Wakselman [1] have shown that the CF3SO2 group increases CH-acidity more in dipolar aprotic solvents than in water or methanol.
In this work we have investigated the nucleophilicities of triflinate-substituted benzyl anions by determining the rate constants of the reactions of carbanions 1 with benzhydrylium ions 2 which have been employed as reference electrophiles.

Plots of the second-order rate constants of these reactions versus the electrophilicity parameters E of the benzhydrylium ions gave the nucleophilicity parameters N and s of these carbanions as defined by eq. 1.

log k2 (20°C) = s (N + E) (1) [2]

Figure 1, which compares the N parameters of triflinate stabilized carbanions with those of other types of carbanions, shows a close similarity of the N-parameters of triflinate and nitro substituted benzyl anions.

Figure 1. Nucleophilicities of different type of carbanions in DMSO.

[1] F. Terrier, E. Kizilian, R. Goumont, C. Wakselman, J. Am. Chem. Soc. 1998, 120, 9496-9503.
[2] a) H. Mayr, B. Kempf, A. R. Ofial, Acc. Chem. Res. 2003, 36, 66-77. b) H. Mayr, A. R. Ofial, Pure Appl. Chem. 2005, 77, 1807-1821. c) H. Mayr, M. Patz, Angew. Chem. 1994, 106, 990-1010; Angew. Chem. Int. Ed. Engl. 1994, 33, 938-957.


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Submitted: 2006-05-31 14:27
Revised:   2009-06-07 00:44