Study of the gas-phase basicity of 1-methylazaindole, 7-methyl-7H-pyrrolo[2,3-b]pyridine, and related compounds

Structures of pyrazolo[1,5-a]pyridine derivatives

“…The bond distances and angles for (2b) are very similar to those of the INDOoptimized geometry for the parent pyrazolo[1,5-a]pyfidine (Catalan et al, 1988), except for the N(1)--N(2) bond length (1.3253/~ in the latter) and the N(1)--: N(2)--C(1) angle (104.1 ° in the latter). Furthermore, the angle S(1)BC(1)--N(2) in (2b) is very similar to the angle S(1)BC(1)--C(2), and the angle S(2)--C(2)~C(1) is also very similar to the angle S(2)--C(2)~C(3), indicating the absence of any steric interaction between their substituents.…”

Study of 7-azaindole in its first four singlet states

“…However, Catalán et al 2 found a different situation in the gas phase as 7-azaindole is intrinsically 1.7 kcal/ mol more basic than pyridine in this state; this suggests that, as expected, the pyrrole ring increases the pyridine basicity of the compound. Thus, Adler and Albert 1 found the protonation pK for 7-azaindole in water to be 4.59; this value is lower than that for pyridine ͑pK = 5.2͒, which suggests that the pyrrole ring slightly decreases the basicity of the pyridine nitrogen.…”

“…35͔͒ is ca. 2 So it is substantially more acidic than phenol ͓⌬G H− 0 = 342.39 kcal/ mol ͑Ref. 36͒ and, judging from the theoretical values in Table III, even lower than that of the compound formed by fusion with a pyridine ring.…”

Product Class 5: Azaindolizines with Two Nitrogen Atoms in the Five-Membered Ring

“…[48] Scheme 10 Synthesis of 3-Ethoxycarbonyl-2-(trifluoromethyl)imidazo[2,1-a]isoquinoline [ Upon reviewing the pertinent literature, some ring closures to the title system can be found that cannot be classified by any of the above methods. Another transformation starting from pyridin-2-amine (9) should also be mentioned here: reaction with the phosphonium-containing enamines 76 leads to the quaternary salts 77 in acceptable yield, and these compounds are transformed by sodium hydroxide to 2-(acylamino)-substituted imidazo[1,2-a]pyridines 78. The transformations are shown in Scheme 11.…”

“…[6] The UV spectra [7] and photophysical properties [7,8] of some derivatives have been studied both experimentally and theoretically, and molecular electrostatic potential maps have been calculated. [9] X-ray determinations have also been carried out. [10] Various derivatives of this ring system show valuable biological properties.…”