M-Nitrostyrene

B. m-Nitrostyrene. In a 250-ml. two-necked flask equipped with a 250° thermometer and an air condenser are placed 30 g. (0.155 mole) of m-nitrocinnamic acid, 2 g. of copper powder, and 60 ml. of dry quinoline (Note 3). The flask is heated with a Bunsen burner to 185-195°, during which time a steady stream of carbon dioxide is evolved. After 2-3 hours (Note 4), the reaction mixture is cooled and poured into a mixture of 75 ml. of concentrated hydrochloric acid and 175 g. of ice. The m-nitro-styrene is isolated by steam distillation, approximately 1 1. of... 

Quinoline that has been purified by steam distillation of an acid solution should be used. Crude quinoline sometimes contains non-basic, high-boiling impurities such as nitrobenzene, which make the purification of m-nitrostyrene more difficult. 

Results of Dulog, Kern et ah, and a few others (27, 31) are summarized in Table I. From the ra values, toward the unsubstituted styrene-peroxy radical, the most reactive styrene—p-methoxystyrene—is three times as reactive as the least reactive, m-nitrostyrene. Thus, the best electron donor shows the highest reactivity (lowest enthalpy of activation) toward the electron-accepting styrene-peroxy radical. The deviations from unity of the rarb products measure the effects of substitution on the selectivity of the peroxy radicals. These products depart more from unity with increasing differences in the electron-donating and accepting properties of the nuclear substituents. The same trends appear within the other styrene combinations. 

In addition to the proton marked Ha in m-nitrostyrene in Figure 13.20, there are two other vinylic protons. Assuming that the coupling constant between the two geminal protons in ArCH=CH2 is 2 Hz and the vicinal coupling constants are 12 Hz (cis) and 16 Hz (trans), describe the splitting pattern for each of these other two vinylic hydrogens. 

Kureshy et al. have reported that ruthenium-Schiff base complexes 27 serve as a catalyst for enantioselective epoxidation of styrene derivatives (Scheme 6B.26) [71], An electronic effect similar to that described in the Mn-salen-catalyzed epoxidation (vide supra) is observed in this epoxidation, that is, an electron-donating group on the catalyst and electron-withdrawing group on the substrate lead to higher enantioselectivity. For example, the epoxidation of styrene with 27c shows modest enantioselectivity (38% ee), whereas that of m-nitrostyrene with 27a exhibits much higher enantioselectivity (80% ee). 

In contrast to the ground-state hydration, the photoaddition of water and of several alcohols to the triplet excited states of m-nitrostyrenes affords the corresponding anti-Markovnikov products58. 

The ability to accept electrons from donors is particularly pronounced in acrylic acid derivatives [85] its alkyl esters [78, 87, 88], acrylonitrile [88], acrylamide, hydroxylacrylates [85], and further in styrenes substituted with an electronegative atom or group m-nitrostyrene, 2,6-dichlorostyrene [86], / -nitrostyrene [89] bicyclobutane-1-carbonitrile [89] lactones /J-propio-Iactone [85], sulfolactone vinyl ketones [87] unsaturated dicarboxylic acids and their derivatives diethyl fumarate, fumaronitrile [90], ROOC—N— N—COOR [86], cyclic anhydrides of diacids [91 ], particularly maleic anhydride [78, 92] ethylenes substituted with electronegative groups [93, 95]... 

Aliphatic nitro compounds show a number of reactions which parallel those of carbonyl chemistry. Primary and secondary nitro compounds exhibit tautomerism paralleling keto-enol tautomerism (Scheme 3.94a). Aliphatic nitro compounds dissolve in aqueous sodium hydroxide with the formation of sodium salts. The resultant anions behave as carban-ions and will condense with aldehydes. An example involves the formation of m-nitrostyrene from nitromethane and benzaldehyde (Scheme 3.94b). 

Figure 13.18fl shows the signal for the proton marked ArCH,=CH2 in m-nitrostyrene, which appears as a set of four peaks in the range 8 6.7-6.9 ppm. These four peaks are in fact a doublet of doublets. The proton in question is unequally... 

Reductions. Disulfides are cleaved, and nitroaryl azides are reduced to the amines without affecting the nitro group or other substituents. However, p.y-unsaturated nitroalkenes are reduced to enones, and m-nitrostyrenes give a-allyloxy arylacetaldoximes in the presence of allyl alcohol. ... 

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