Nucleophilicities of the Anions of Arylacetonitriles and Arylpropionitriles in Dimethyl Sulfoxide

Abstract

The rates of the reactions of the colored para-substituted phenylacetonitrile anions 1a-c and the phenylpropionitrile anions 2a-c with Michael acceptors (3a-u) were determined by UV-vis spectroscopy in DMSO at 20 degrees C. The reactions follow second-order kinetics, and the corresponding rate constants k(2) obey the linear-free-energy relationship log k(2)(20 degrees C) = s(N + E), from which the nucleophile-specific parameters N and s of the carbanions 1a-c and 2a-c have been derived. With nucleophilicity parameters from 19 < N < 29, they are among the most reactive nucleophiles which we have so far parametrized. In DMSO, the nucleophilicity of the tert-butoxide anion is comparable to that of the p-cyanophenylacetonitrile anion 1b.

Di‐ and Triarylmethylium Ions as Probes for the Ambident Reactivities of Carbanions Derived from 5‐Benzylated Meldrum’s Acid

“…With nucleophilicity parameters 12< N <15, the 5‐benzyl‐ substituted anions of Meldrum’s acid have similar nucleophilic C‐reactivities as the anion derived from the parent Meldrum’s acid (Table 3), in line with previous observations that methyl groups at the carbanionic center of diethyl malonate or acetylacetonide anions have little effect on their nucleophilic reactivities 9. 14 Obviously, C‐nucleophilicity is much greater than the hydride‐donating ability, as in none of the reactions of the carbanions 1 with the benzhydrylium ions 3 the formation of the hydride abstraction products 2 was observed.…”

Nucleophilic Substitution Reactions of 2‐Methoxy‐3‐X‐5‐nitrothiophenes: Effect of Substituents and Structure–Reactivity Correlations

“…Moreover, the nucleophilicity scale defined by Eq. encompasses a range of 38 orders of magnitude (−8.80 ≤ N ≤ 28.95 ):Recently, Terrier and co‐workers have investigated S N Ar reactions of 7‐chloro‐4,6‐dinitrobenzofuroxan 6 and 7‐chloro‐4,6‐dinitrobenzofurazan 7 with a series of weak carbon nucleophiles (substituted indoles, azulene, and 1,2,5‐trimethylpyrrole) and have demonstrated for the first time that it is possible to describe the second‐order rate constants through the relationship proposed by Mayr and co‐workers (Eq. ) .…”

Comparison of the Electrophilic Reactivities of N‐Acylpyridinium Ions and Other Acylating Agents

“…General: Acetylacetone (6-H), diethyl malonate (7-H), ethyl cyanoacetate (8-H), malononitrile (9-H), nitromethane (11-H), nitroethane (12-H), tert-butylamine (13), isopropylamine (14), benzylamine (15), allylamine (16), ethanolamine (17), n-propylamine (18), n-butylamine (19), N,N-bis(2-methoxyethyl)amine (21), di-n-propylamine (22), diethylamine (23), morpholine (24), piperidine (25), pyrrolidine (26), and methylhydrazine (28) were purchased and purified by distillation prior to use. 4-Nitrophenyl benzoate (1), benzoic anhydride (2), acetic anhydride (3), benzoyl chloride (4), 4cyanophenylacetonitrile (10-H), hydrazine monohydrate (20·H 2 O), tetra-n-butylammonium benzoate (29), tetra-n-butylammonium 4nitrobenzoate (30), potassium tert-butoxide, p-toluenesulfonic acid probe (5 mm light path) by fiber optic cables with standard SMA connectors.…”

“…The N-acyl-pyridinium chloride 5 was synthesized by treatment of benzoyl chloride (4) with an equimolar amount of 4-(dimethylamino)pyridine (DMAP) in acetonitrile followed by precipitation (Et 2 O) and isolation of the product. [17] [c] From ref. As demonstrated for the reaction of 5 with benzylamine (15), both methods gave rate constants that differed by less than 3 %.…”