Diversity Oriented Heterocyclizations of Pyruvic Acids, Aldehydes And

Diversity oriented heterocyclizations of pyruvic acids, aldehydes and 5-amino-N-aryl-1H-pyrazole-4-carboxamides: catalytic and temperature control of chemoselectivity

Yana I. Sakhno, Svetlana V. Shishkina, Oleg V. Shishkin, Vladimir I. Musatov, Elena V. Vashchenko, Sergey M. Desenko, Valentin A. Chebanov*

Division of Functional Materials Chemistry, State Scientific Institution “Institute for Single Crystal” NAS of Ukraine, Lenin Ave. 60, Kharkiv Ukraine, 61001

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X-ray analysis of compound 3g:

It was found that in 3-(2-methoxyphenylcarbamoyl)-7-(4-methylphenyl)-4,7-dihydropyrazolo[1,5-a]pyrimidine-5-carboxylic acid 3g pyrazole ring and 2-methoxyphenylcarbamoyl substituent lie in the plane within 0.02 Å. Such position of these fragments relatively each other is stabilized by the N(1)-H(1N)…O(3): H…O 2.30 Å, N-H…O 119° and C(17)-H(17)…O(3): H…O 2.23 Å, C-H…O 122° weak intramolecular hydrogen bonds. Methoxy group is almost coplanar to the plane of aromatic ring (the С(22)-О(4)-С(21)-С(20) torsion angle is -8.2(5)°) in spite of relatively strong repulsion between atoms of methyl group and aryl ring (shortened intramolecular contacts H(20)…C(22) 2.51 Å (the van der Waals radii sum [1] is 2.87 Å), H(20)…H(22c) 2.33 Å (2.34 Å), H(20)…H(22b) 2.27 Å (2.34 Å), H(22b)…C(20) 2.68 Å (2.87 Å), H(22c)…C(20) 2.80 Å (2.87 Å)).

Figure 1 Molecular structure of compound 3g (X-ray diffraction data)

Dihydropyrimidine ring adopts very flattened boat conformation (the puckering parameters [2]: S = 0.09, Θ = 70.6°, Ψ = 15.5°). Deviations of the N(1) and С(4) atoms from the mean plane of the remaining atoms of the ring are -0.06 Å and -0.04 Å, respectively. Tolyl substituent is turned relative to the plane of dihydrocycle (the N(3)-C(4)-C(8)-C(9), the torsion angle is -42.3(5)°), which leads to the appearance of the short contact Н(4)…Н(13) 2.32 Å (2.34 Å). Carboxylic group is coplanar to dihydropyrimidine cycle plane owing to the attractive interaction H(1N)…O(1) 2.37 Å (2.46 Å).

References

1.  Zefirov YV (1997) Reduced Intermolecular Contacts and Specific Interactions in Molecular Crystals. Crystallography Reports42: 865–886.

2.  Zefirov NS, Palyulin VA, Dashevskaya EE (1990) Stereochemical studies. XXXIV. Quantitative description of ring puckering via torsional angles. The case of six-membered rings. J Phys Org Chem 3: 147–158. doi: 10.1002/poc.610030304