Stanislav Man

New fused heterocycles by combined intra-intermolecular criss-cross cycloaddition of nonsymmetrical azines ☆

Thermally induced intra-intermolecular criss-cross cycloaddition of nonsymmetrical azines in the presence of phenyl isocyanate is described. This one-pot reaction gives heterocyclic compounds containing three fused five-membered rings. The molecular and crystal structure of the products is reported and discussed.

Molecular and Crystal Structures of Three Berberine Derivatives

Berberine azide, berberine thiocyanate, and 8-cyano-8H-berberine were prepared from berberine chloride, a quaternary protoberberine alkaloid. The molecular and crystal structures of all compounds are reported and discussed.

BERBERINE AND COPTISINE IN LIQUID AMMONIA

In liquid ammonia, quaternary protoberberine alkaloids berberine and coptisine afforded unstable adducts, 8-amino-8H-berberine and 8-amino-8H-coptisine, respectively. Their structures were supported by X-ray analysis and mass spectra.

Substituted homoallenyl aldehydes and their derivatives. Part 2: Azines

This paper deals with the preparation of a variously substituted non-symmetrical azine set. The starting molecule for their preparation was a protected hydrazone. The protection was performed applying Zwierzak’s method. This procedure is based on the transfer of hydrazine to diethylhydrazidophosphate, which reacts with aldehydes to produce protected hydrazones. In the second step of the procedure, under the action of sodium hydride, the addition of another aldehyde affords non-symmetrical azines in the reaction with the protected hydrazine. The procedure was shown to be a useful and effective method. In this, the second part of our study, we present results devoted to the preparation and full identification of non-symmetrical azines.

Substituted homoallenyl aldehydes and their derivatives. Part 1: Homoallenyl aldehydes and protected hydrazones

The paper presents a simple synthesis of substituted propargyl vinyl ethers and their subsequent thermally-initiated Claisen rearrangement leading to various 3-substituted homoallenyl aldehydes. Several methods, including Sonogashira coupling, base-promoted substitution on the triple bond by sodium amide or butyllithium, and the preparation of substituted propargyl alcohols, were used in the initial step. Phosphate-protected homoallenyl aldehyde hydrazone derivatives were synthesised and fully characterised. The stereochemistry of 9-anthracene carbaldehyde hydrazone, which, surprisingly, afforded both cis and trans isomers, was established using X-ray analysis.

Homoallenyl azines in criss-cross cycloaddition reactions

Thermally initiated combined intra-intermolecular criss-cross cycloadditions of substituted nonsymmetrical allenyl azines with isocyanate or isothiocyanate dipolarophiles were investigated. Substituted 1,3,10-triazatricyclo[5.2.1.04,10]dec-6-en-2-ones or -dec-6-ene-2-thiones were obtained as the main products in moderate to very good yields. The thermal stabilities of the tricyclic adducts in reactions with the competing reactive dipolarophile dimethyl acetylenedicarboxylate were studied and are discussed. In some cases, substituted 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazoles were found as side products. This reaction showed high atom economy and in all cases we observed the presence of one diastereoisomer and regioisomer only, which was clearly revealed by crystallographic analysis.Graphical abstract