N Me pyrroles

Treatment of substituted pyrrole 171a (R = pyrrol-2-yl) with triphosgene and triethylamine leads to pyrrolo-benzothiazepine 172 in 35% yield (Scheme 34 (1994M1283)). Similarly, substituted pyrrole 171b (R = N-Me-pyrrol-3-yl) produces pyrrolo-benzothiazepine 175. 

Approximate additivity rules for the chemical shifts of azoles have been reported (110). For the pyrrole-type nitrogen atoms, the shifts may be related to that of N-Me-pyrrole [25]. They are composed of the algebraical summation of the following contributions ... 

Fig> 11-9 Results from AC conductivity studies on lightly doped Poly(N-Me-pyrrole) films, after Singh et. al. [403], reproduced with permission. 

In the Ingan and Lundstrdm work, an AZ-Si/poly(N-Me-pyrrole) SC/CP interface was used, with application as a fast optical memory envisioned. In the write step of this memory, the CP was oxidized by illuminating the SC. In the erase step, a negative (cathodic or reducing) potential was applied to the CP, returning it to its original, de-doped state. This device however required the use of liquid electrolyte, and switching times were of the order of ms. It thus did not utilize the solid state and ultrafast photonic capabilities of such an interface. 

Additional kinetic evidence supporting molecular iodine as an iodinating species is sparse. Li325 found that the iodination of tyrosine in acetate buffers at 25 °C showed the mixed inverse dependence on iodide ion concentration noted above, so that part of the reaction appeared to involve the molecular species. Subsequently, Doak and Corwin326 found that the kinetics of the iodination of (N-Me)-4-carboethoxy-2,5-dimethyl- and (N-Me)-5-carboethoxy-2,4-dimethyl-pyrroles in phosphate buffers in aqueous dioxane at 26.5 °C obeyed equation (162), viz. 

A The reaction conditions of the first step are those of the Vilsmeier reaction (see above). With the cleclrophilc Me,N =CHCL pyrrole is attacked at C-2, rather than at C-3, and after hydrolysis 2-... 

Singh et al. have used perhydrol,3-heterocycle 253 as carbonyl equivalent for acid (TFA)-catalyzed dipyrro me thane 254 synthesis (Scheme 99) using only stoichiometric amounts of pyrrole/N-methyl pyrrole and products were obtained in good yield with formation of tripyrromethanes 255 (05T6614,05SC929). 

Metallation occurs more readily with N-NMcj and N-COjBu-t than with N-Me derivatives of pyrrole ... 

The adducts (92 R = PhCO or COOBu ") of perf luorobut-2-yne, CF CECCF, to N-substituted pyrroles have been degraded to 3,4-bis(trifluoromethyl)pyrroles (93) by two methods in the former, the adducts were first hydrogenated at the unsubstituted double bond and then heated to eliminate ethylene,while in the latter, the adducts were treated with mesitonitrile oxide, 2,4,6-Me C H2C=N -0, which removed the ethylene unit in the form of the isoxazole (94). 

Contributor 7.12 illustrates the direct interaction of donor N-Me and acceptor C=N, which is a major contributor to the hybrid. The negative charge on N is acceptable and of course is involved in pyridine-type delocalization. As a result, the Ia of 79 for imidazole is close to that of pyrrole (85) and thiophene (81.5). 

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