Selenium heterocycles. XXXIX. Synthesis of thieno[3, 4-d]thiazole, thieno[3, 4-d]selenazole, selenolo[3, 4-d]thiazole and selenolo[3, 4-d]selenazole

Dimroth rearrangement-based synthesis of novel derivatives of [1,3]selenazolo[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine as a new class of selenium-containing heterocyclic architecture

As a part of our ongoing endeavor towards developing novel heterocyclic architectures, a number of novel Se-containing tricyclic heterocycles of the type [1,3]selenazolo[5,4-e][1,2,4]triazolo[1,5-c]pyrimidine have been synthesized through heteroannulation of a newly produced hydrazino derivative of selenazolo[4,5-d]pyrimidine with either orthoesters or carbon disulfide in pyridine followed by S-alkylation. Moreover, the multistep protocol employed in this investigation provides a new insight into the Dimroth rearrangement in both acidic and basic media as a means for the cyclocondensation of triazole on the selenazolopyrimidine framework leading to selenazolotriazolopyrimidines. The synthesis of new derivatives of novel selenazolotriazolopyrimidines via Dimroth rearrangement in both acidic and basic media is presented.

Synthesis and Single Crystal Structures of Substituted-1,3-Selenazol-2-amines

The synthesis and X-ray single crystal structures of a series of new 4-substituted-1,3-selenazol-2-amines is reported. The efficient preparation of these compounds was carried out by two-component cyclization of the selenoureas with equimolar amounts of α-haloketones. The selenoureas were obtained from the reaction of Woollins’ reagent with cyanamides, followed by hydrolysis with water. All new compounds have been characterized by IR spectroscopy, multi-NMR (¹H, ¹³C, ⁷⁷Se) spectroscopy, accurate mass measurement and single crystal X-ray structure analysis.

The [3 + 2] cycloaddition reaction of thiazole carbene-derived C-C-Se 1,3-dipoles: a concise and highly efficient strategy for the construction of multifunctional dihydroselenophenes and selenopheno[2,3-b]pyrazines

The first study on the reaction of C(+)-C-Se(-) 1,3-dipoles with electron-deficient alkenes and alkyne is reported. 2-Arylselenocarbamoylthiazolium inner salts, the unique thiazole carbene-derived C(+)-C-Se(-) 1,3-dipoles, reacted efficiently with methoxycarbonylallenes or dimethyl acetylenedicarboxylate to produce dihydroselenophenes or selenopheno[2,3-b]pyrazines, respectively, in high yields. Both reactions probably proceeded via a [3 + 2] cycloaddition of C(+)-C-Se(-) 1,3-dipoles with alkenes or alkyne followed by different transformations of the thiazole-spiro-selenophene intermediates. This work provides a concise and efficient strategy for the construction of multifunctional dihydroselenophenes and selenopheno[2,3-b]pyrazines, which are not easy accessible by other methods.

Supramolecular Synthesis of Selenazoles Using Selenourea in Water in the Presence of β-Cyclodextrin under Atmospheric Pressure

Selenazoles were synthesized from alpha-bromo ketones and selenourea in the presence of beta-cyclodextrin in water at 50 degrees C under atmospheric pressure.