Nuclear Magnetic Resonance Studies of Meisenheimer Complexes

N-Methylpicramide–methoxide ion interactions: proton abstraction versus σ-complex formation

“…The agreement among the values of K,, calculated using absorbance data collected at the three wavelengths, confirms the validity of eq. [2] and 1: 1 stoichiometry of species Y.…”

“…[2], were found to increase by a factor of approximately four as the total base concentration in solution varied from 3.75 x 10-j M to 19.0 x lo-' M. It seems unlikely that the variation in Kl is due to an ionic strength effect because a comparable increase in Kl values was observed when the experiments were carried out under conditions in which the base concentration varied from 3.75 x 10-j M to 20.0 x 10-j M but the ionic strength was maintained constant at 0.20 M with added (C,Hj),NC104.…”

Nuclear magnetic resonance studies of cyanide ion–2,4,6-trinitroanisole σ-complexes

“…Representative data for these systems are listed in Table I. As in the case of the methoxide ion adducts, the methoxyl group hydrogens in the 1 complex absorb further upfield than the methoxyl group hydrogens in the 2 complex, while the H, protons in the 1 complex absorb further downfield than the H, proton in the 2 complex (3).…”

“…spectrum of 2,4,6-trinitroanisole (TNA) in deuteriochloroform at -30 "C shows resonance absorptions at 9.08 and 4.27 p. the absorption at 5.73 is assigned to the HB hydrogen in complex 2. The assignments are made on the basis of the chemical shifts observed in the cyanide ion complexes of 1,3,5-trinitrobenzene and 2,4,6-trinitrotoluene (2) and the methoxide ion complexes of 2,4,6-trinitroanisole (3,4,(7)(8)(9). Representative data for these systems are listed in Table I.…”

Oxidative carbon-carbon coupling. II. Effect of ring substituents on the oxidative carbon-carbon coupling of arylmalonic esters, arylmalodinitriles, and arylcyanoacetic esters

“…'l After crystallization from ethanol there was obtained 40% of 5b: mp 57-57.5'; nmr (CCla) 6 2.40 (s, 3, p-CHa), 5.08 (s, 1, tertiary H), 7 Arylcyanoacetic Esters 7b, 7c, l l a , and 1lb.-Methyl otolylcyanoacetate (7b) was prepared in 64% yield from o-methylbenzyl cyanide, bp 118-128" (12 mm), and dimethyl carbonate (3 molar excess) with CH,ONa in refluxing toluene as described for ethyl pheny1cyanoacetate:l8 bp 106-114" (0.3 mm); nmr Methyl 2,4,6-trimethylphenylcyanoacetate (1 la) was prepared from 2,4,6-trirnethylbenzyl cyanide14 and dimethyl carbonate with NaH in dimethoxyethane as described for methyl phenylcyanoacetate.' The crude product was not distilled but was immediately recrystallized from ether-cyclohexane (1 : 9), giving a 21% yield of colorless material, mp 99.6-101.8'.…”