2363-27-1Relevant articles and documents
Dual nucleophilic substitution reactions of O,O-diethyl 2,4-dinitrophenyl phosphate and thionophosphate triesters
Aguayo, Raul,Arias, Felipe,Canete, Alvaro,Zuniga, Carolina,Castro, Enrique A.,Pavez, Paulina,Santos, Jose G.
, p. 202 - 211 (2013/03/14)
The reactions of the title compounds with phenoxides, secondary alicyclic (SA) amines, and pyridines, in 44 wt% ethanol-water, at 25°C and an ionic strength of 0.2 M, were subjected to kinetic and product studies. From analytical techniques (HPLC and NMR), two pathways were detected (nucleophilic attack at the phosphoryl center and at the C-1 aromatic carbon) for the reactions of all the nucleophiles with the phosphate (2) and for the pyridinolysis of the thionophosphate (1). Only aromatic nucleophilic substitution was found for the reactions of 1 with phenoxides and SA amines. For the dual reactions, the nucleophilic rate constants (kN) were separated in two terms: documentclass{article}usepackage{amssymb} pagestyle{empty}begin{document}k-{rm N}^{rm P}end{document} and documentclass{article}usepackage{amssymb}pagestyle{empty}begin{document}k-{ rm N}^{{rm Ar}}end{document}, which are the rate constants for the corresponding electrophilic centers. The absence of a break in the Bronsted-type plots for the attack at P is consistent with concerted mechanisms. The Bronsted slopes, βAr 0.32-0.71, for the attack at the aromatic C-1, are in agreement with stepwise mechanisms where formation of a Meisenheimer complex is the rate-determining step. 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: 202-211, 2013 Copyright
P(i-BuNCH2CH2)3N: an efficient promoter for the microwave synthesis of diaryl ethers
Raders, Steven M.,Verkade, John G.
, p. 3507 - 3511 (2008/09/21)
With the title proazaphosphatrane as a promoter, the coupling of aryl fluorides with aryl TBDMS ethers under microwave conditions gave moderate to high yields of the desired products at low catalyst loadings and in short times. In this methodology, electron deficient aryl fluorides possessing substituents, such as nitro, cyano, and ester, were coupled with sterically demanding aryl TBDMS ethers as well as with aryl TBDMS ethers bearing a variety of functionalities such as methoxy, halo, and cyano groups.
The α-effect in SNAr substitutions - Reaction between oximate nucleophiles and 2,4-dinitrofluorobenzene in aqueous solution
Moutiers, Gilles,Le Guevel, Eric,Cannes, Celine,Terrier, Francois,Buncel, Erwin
, p. 3279 - 3284 (2007/10/03)
The second-order rate constants (k1ArO,k1Ox for substitutions of 2,4-dinitrofluorobenzene (DNFB) by a series of phenoxide and oximate nucleophiles have been measured in aqueous solution at 25 °C, using both a potentiometric procedure involving the use of a fluoride ion selective electrode (FISE) and a classical spectrophotometric procedure. While the rate data for the phenoxide ions conform to a linear Broensted plot with a slope (βNu = 0.71) fitting the 0.5-0.7 range commonly found for SNAr reactions, those for the various oximates studied do not define a meaningful linear plot. Interestingly, the observed variations in k1Ox reveal a tendency of the reactivity of oximates of pKa > 7.5-8 to level off rapidly, a situation reminiscent of that encountered in other nucleophilic reactions of these species at carbonyl and phosphonyl centres. Our current finding reinforces the idea of a general oximate behaviour pattern originating from an especially strong need for partial desolvation before nucleophilic attack, i.e., asynchronicity or TS imbalance. A major consequence of the observed levelling off is that the extra reactivity reflecting the α character of oximate nucleophiles decreases significantly in magnitude on going from weakly basic oximates (k1Ox/k1ArO ≈ 100) to strongly basic ones (k1Ox/k 1ArO ≈ 10). On the basis of the k1Ox/k1ArO ratio measured at low pKa, the α-effect associated with the SNAr substitution of DNFB is of the same order as that measured for other reactions of oximates at sp2-carbon centres.
