Amino group orienting effect

A new example of the reactivity of 3,4-pyridyne as a dienophile was reported (the conversion by cyclopentadiene ) and a remarkable orienting effect of the amino group on the addition of ammonia to the triple bond in amino derivatives of 3,4-pyridyne, e.g., the addition of the amide ion to C-4 in 5-amino-3,4-pyridyne. ... 

For a review of the directing and orienting effects of amino groups, see Chuchani, G. in Patai The Chemistry of the Amino Group Wiley NY, 1968, p. 250 for ether groups see Kohnstam, G. Williams, D.L.H. in Patai The Chemistry of the Ether Linkage Wiley NY, 1967, p. 132. 

For substituents with —I, +M effects, the orienting effect of such substituents (halogens, alkoxy, thioalkoxy, amino, alkylamino, etc.) is similar to that of alkyl groups. If the substituent is in position 2, further substitution occurs at position 5 if it is in position 3, substitution occurs preferentially at 2, unless the steric requirement forces the incoming substituent to position 5. 

The nitration of aniline in the presence of a large amount of strong sulfuric acid results wholly in the formation of m-nitro-aniline, but the similar nitration of dimethylaniline gives principally a mixture of the ortho- and para-derivatives. Mono-methylaniline stands between aniline and dimethylaniline in respect to the orienting effect of its amino group it yields a considerable amount of the m-nitro- compound—and dimethylaniline is preferred for the preparation of tetryl. Commercial dimethylaniline contains a certain amount of monomethylaniline, from which it is extremely difficult to free it, and this in the manufacture of tetryl is converted in part into 2,3,4,6-tetranitro-phenylmethylnitramine, or m-nitrotetryl, pale yellow, almost white, crystals from benzene, m.p. 146-147.087... 

The substantial electric field enveloping the excited state of 1 is to be expected from its ICT nature. In fact a dipole moment of 1 ID can be measured [37], Of course, such fields are vectorial and they can help or hinder electron transfer depending on relative orientation. Such effects are clearest when the electron transfer is not heavily biased thermodynamically. The near isoergonic condition of 1 suits us nicely. The 4-amino group is close to the positive terminal of the excited state dipole whereas the imide unit houses the negative end. So, 1 fits the happy situation where the incoming photoinduced electron is attracted towards the lumophore. On the other hand, l s regioisomer 3 repulses... 

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