Nucleophilic Reactivities of Bis‐Acceptor‐Substituted Benzyl Anions

Abstract

The kinetics of the reactions of bis‐acceptor‐substituted benzyl anions (PhCXY–, X,Y = CN, CO2Et, COPh, SO2Ph) with benzhydrylium ions and quinone methides (reference electrophiles) have been determined in dimethyl sulfoxide solution at 20 °C. The reactions follow second‐order kinetics, first order with respect to the electrophile and first order with respect to the carbanion. The addition of 18‐crown‐6 ether, which efficiently coordinates to the anions' counter ions K+, did not affect the kinetics, which indicates that the measured rate constants refer to the reactivities of the nonpaired carbanions. Comparison with the reactivities of the structurally analogous secondary carbanions HCXY– shows that replacement of H at the carbanionic center by Ph reduces the nucleophilic reactivities towards a reference benzhydrylium ion by factors in the range of only 1.2 (X,Y = SO2Ph) to 6 (X,Y = CO2Et). The plots of lg k2 versus the electrophilicity parameters E of the reference electrophiles are linear, thereby indicating that the correlation lg k2(20 °C) = sN(E + N), which characterizes nucleophiles by the two solvent‐dependent parameters sN and N and electrophiles by the parameter E, is applicable. In this way, it becomes possible to integrate these carbanions into our comprehensive nucleophilicity scale, which provides a direct comparison of the nucleophilic reactivities of different families of compounds.

Structure–Activity Relationships of Pyrazolo[1,5-a]pyrimidin-7(4H)-ones as Antitubercular Agents

“…Intermediate 9 in turn was prepared by coupling benzyl cyanide 7 with dimethyl carbonate 8 . On the other hand, the coupling reaction between iodobenzene 11 and malononitrile 12 provided phenylmalononitrile 13 , 13 which generated the diamino pyrazole 14 after the reaction with hydrazine. 12 The fused heterocyclic P4 was finally generated by an intramolecular condensation reaction after the reaction with β-ketoester 5 .…”

“… 27 − 29 The synthetic procedures of P1 ( 11 , 29 ) and P2 ( 30 ) were followed by the previously reported procedure with some modifications. The key intermediate 10 for the synthesis of P3 , 12 , 31 intermediate 14 for the precursor of P4 , 12 , 13 and intermediate 17 for the P5 ( 14 ) were prepared using the previously reported procedure with some modifications.…”

“…Chemistry. 1 H and 13 C NMR spectra were recorded on a Varian Mercury-300 NMR spectrometer or a Bruker AVANCE III HD NanoBay 400 MHz spectrometer, and chemical shifts were measured in ppm relative to the specific solvent signal. Routine mass and purity analyses (LRMS) were performed on an HP Agilent LC/MS series 1100 system equipped with a reverse phase column (Agilent Poroshell 120 EC-C18, 2.7 μm, 50 × 2.1 mm) and photodiode array detector coupled to an Agilent 1946 DSL quadrupole mass selective detector using electrospray ionization (ESI).…”

“…General syntheses of 1 , 2 , 4 , and P6 – P27 and the final cyclocondensation reactions for P3 – P5 were performed using the previously reported procedure with some modifications. − The synthetic procedures of P1 , and P2 were followed by the previously reported procedure with some modifications. The key intermediate 10 for the synthesis of P3 , , intermediate 14 for the precursor of P4 , , and intermediate 17 for the P5 were prepared using the previously reported procedure with some modifications.…”

Reactivity of Electrophilic Trifluoromethylating Reagents

“…The authors have cited additional references within the Supporting Information (Ref. [22][23][24][25][26][27][28][29]). [5,20], reactivity parameters N and s N were taken from ref.…”