Diversification of a thieno[2,3-d]pyrimidin-4-one scaffold via regioselective alkylation reactions.

The 2-aryl-2,3,5,6,7,8-hexahydro[1]benzothieno[2,3-d]pyrimidin-4(1H)-ones and 2-aryl-5,6,7,8-tetrahydro[1]benzothieno[2,3-d]pyrimidin-4(3H)-ones have been diversified by alkylation reactions, applying benzylchlorides and N-substituted 2-chloroacetamides as alkylating agents. Under the found uniform conditions the substitution direction does not depend on the structure of the alkylating agent and gives monoalkylated products in high yields with simple workup. The alkylation of the 2,3-dihydropyrimidin-4(1H)-one derivatives proceeds onto the N1-position; however, in the case of pyrimidin-4(3H)-ones the O-alkylated products are formed selectively. An alternative strategy for the synthesis of the N1-benzyl-2,3-dihydropyrimidin-4(1H)-one derivatives is also developed. It applies the redaction of N2-substituted Gewald's amides with aromatic aldehydes and allows simple introduction of various substituents in the final molecule.

Efficient methodology for selective alkylation of hydrazine derivatives.

Formation and use of a nitrogen dianion for selective hydrazine alkylation is reported. The scope and limitations of a new method were demonstrated. The novel method provides fast and easy access to substituted hydrazines, which are widely used as drugs, pesticides, and precursors for a variety of compounds in organic synthesis. [reaction: see text]

Electronic structure and solvatochromism of merocyanines NMR spectroscopic point of view.

(1)H and (13)C NMR spectra of two series of malononitrile-based merocyanines, which possess positive and negative solvatochromism have been in detail investigated in low polar chloroform and polar dimethyl sulfoxide (DMSO). Careful attribution of signals in spectra has been made with the help of two-dimensional NMR experiments (COSY, NOESY, HMBC, and HMQC). Hence, the dependence of merocyanines electronic structure on their chemical structure and solvent nature has been studied by this powerful method. It has been shown that there exists a good correlation between the calculated charges on carbon atoms of a polymethine chain and their chemical shifts in (13)C NMR spectra. The influence of solvent polarity on bond orders for dyes with positive and negative solvatochromism is also observed. The comparison of (13)C NMR spectra of merocyanines and corresponding parent ionic dyes allows to determine their sign of solvatochromism irrespectively of electronic spectra, and also to find the key atoms of chromophore whose signals in (13)C NMR spectra are most informative.