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Using frustrated Lewis pairs to explore C–F bond activation

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Abstract

Our interest in C–F bond activation prompted an investigation of the reactions of PhC(O)CF3 with a superbasic proazaphosphatrane (Verkade's base) and a corresponding FLP. The reaction of PhC(O)CF3 with P(MeNCH2CH2)3N in a 2 : 1 ratio generates [FP(NMeCH2CH2)3N][PhC(O)CF2COCF3Ph]. While this salt was not isolable, the anion could be derivatized to allow the isolation of [PhC(O)CF2C(OSiMe2tBu)CF3Ph], 1. To further probe this C–F bond activation, the FLP P(MeNCH2CH2)3N/BPh3 was allowed to react with PhC(O)CF3, which afforded the salt [PhC(CF2)OP(MeNCH2CH2)3N][FBPh3], 2. Insights into the mechanism of the reaction of the proazaphosphatrane with PhC(O)CF3 have emerged from the reactivity of 2 and these have been augmented by DFT computations. Salt 2 could be readily converted to the triflate derivative 3, which was a viable synthon for further C–F bond reactivity. Sequential reaction with Na[HBEt3] afforded the salts [PhC(CF(H))OP(MeNCH2CH2)3N][O3SCF3], 4 and [PhC(CH2)OP(MeNCH2CH2)3N][O3SCF3], 5. Interestingly, the formation of 5 contrasts with the formation of [HP(MeNCH2CH2)3N][PhC(CH2)OB(C6F5)3], 6 observed following the reaction of the FLP P(MeNCH2CH2)3N/B(C6F5)3 with PhC(O)Me. Thus these differing FLP protocols provide avenues to salts containing either an enolate derived cation or anion.

Graphical abstract: Using frustrated Lewis pairs to explore C–F bond activation

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Article information


Submitted
29 Nov 2019
Accepted
19 Dec 2019
First published
23 Dec 2019

Dalton Trans., 2020, Advance Article
Article type
Paper

Using frustrated Lewis pairs to explore C–F bond activation

A. I. Briceno-Strocchia, T. C. Johnstone and D. W. Stephan, Dalton Trans., 2020, Advance Article , DOI: 10.1039/C9DT04588K

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