Deactivators moderate

Solutions of alkali metal or ammonium nitrates in trifiuoroacetic anhydride are useful nitrating agents for a range of activated to moderately deactivated substrates and particularly... 

Heavy mass-transfer limitations and moderately deactivated catalyst... 

Parabanic acid (86) has been shown to produce highly electrophilic species in superacidic CF3SO3H, and the resulting electrophile is capable of reacting with and moderately deactivated arenes.40 The superacid-promoted condensation reaction of parabanic acid with benzene (and other arenes) in CF3SO3H provides satisfactory yields of the 5,5-diarylhydantoins (eq 30),... 

Reaction of acetal 104 with benzene in the presence of CF3SO3H leads to product 107 in high yield. This conversion involves formation of the ammonium-carboxonium dication (105), a reactive dication possessing some 1,3-dicationic character. Reaction with benzene and subsequent loss of methanol generates another reactive dication (106), which then gives the product. The superelectrophilic character of the ammonium-carboxonium dications is indicated by their reactions with moderately deactivated arenes, such as o-dichlorobenzene. 

As mentioned, 2-oxazolines may form a ring-opened distonic superelectrophile in reactions in superacid. These carboxonium-carbenium dications are capable of reacting with benzene and moderately deactivated substrates.2 For example, the optically active oxazoline (94) reacts in CF3SO3H to generate the chiral dication (95) and this superelectrophilic species is capable of reacting with o -dichlorobenzene in fair to modest yield and diastereoselectivity (eq 35). 

Peng, X., Fukui, N., Mizuta, M. and Suzuki, H. Nitration of moderately deactivated arenes with nitrogen dioxide and molecular oxygen under neutral conditions. Zeolite-induced enhancement of regioselectivity and reversal of isomer ratios, Org. Biomol. Chem., 2003, 1, 2326-2335. 

O II —CH O O II II —CR —COH Moderately deactivating meta Inductive and resonance withdrawers... 

Nitration. Regioselective mononitration (but no further) of moderately deactivated arenes is accomplished with urea nitrate or nitrourea, despite their use in excess. 

The moderately deactivating substituents all have carbonyl groups directly attached to the benzene ring. Carbonyl groups withdraw electrons both inductively and by resonance. 

All moderately deactivating and strongly deactivating substituents direct an incoming electrophile to the meta position. 

The (irst is actually the major product the directing effect of the activating ring oxygen to C5 wins out over that of the moderately deactivating COOCHj group to C4. 

The methoxyl group in (a) is ortho-para directing and strongly activating.The sulfonic acid group in (b) is meta directing and moderately deactivating. 

Moderate deactivators are groups that exhibit a it bond to an electronegative atom, where the IT bond is conjugated with the aromatic ring. Below are several examples. 

Analyze the starting material. The two substituents are the methoxy group, which is a moderate activator, and the acyl group, which is a moderate deactivator. 

Meisenheimer complex 899 moderate activators 881 moderate deactivators 882 nitration 866 nitronium ion 866 nucleophilic aromatic substitution 898... 

Cannot perform Friedel-Crafts on moderately deactivated ring... 

We will summarize all of this information in one complete chart, but for now let s move on to moderate deactivators. 

Therefore, this group is a moderate deactivator. Numerous other similar groups can also withdraw electron density from the ring. Here is a list of many examples ... 

Try to predict what kind of group it is (a strong activator, a moderate activator, a weak activator, a weak deactivator, a moderate deactivator, or a strong deactivator). 

Answer This group does not have a lone pair next to the ring, and it is not an alkyl group. Therefore, it is not an activator. This group has a pi bond to an oxygen atom (next to the ring), and therefore, it is a moderate deactivator. 

For each of the following substituents, determine what kind of group it is (a strong activator, a moderate activator, a weak activator, a weak deactivator, a moderate deactivator, or a strong deactivator). Place your answer on the space provided. Try to do this without looking at the chart that we constructed. You won t have access to this chart on an exam. Try to remember and apply the explanations that we used. 

To answer this question, we must predict the directing effects of the group that is currently on the ring. We recognize that this group is a moderate deactivator, which means that it must be a meta director. So, we predict the following product... 

The group on the right is a moderate deactivator (make sure you know why), so it directs meta to... 

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