First synthesis of 1,3-oxaselenepanes

First Exclusive Stereo- and Regioselective Preparation of 5-Arylimino-1,3,4-Selenadiazole Derivatives: Synthesis, NMR analysis, and Computational Studies

Isoselenocyanates are valuable coupling partners required for preparing key chemical intermediates and biologically active molecules in an accelerated and effective way. Likewise, (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides have been employed in numerous one-step heteroannulation reactions to assemble the structural core of several various kinds of heterocyclic compounds. Here, we describe the inverse electron demand 1,3-dipolar cycloaddition reaction of isoselenocyanates with a variety of substituted (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides to generate, regioselectively and stereoselectively, a series of 5-arylimino-1,3,4-selenadiazole derivatives comprising a multitude of functional groups on both aryl rings. The synthetic method features gentle room-temperature conditions, wide substrate scope, and good to high reaction yields. The selenadiazoles were separated by gravity filtration in all instances and chemical structures were validated by multinuclear NMR spectroscopy and high accuracy mass spectral measurements. First conclusive molecular structure elucidation of the observed 5-arylimino-selenadiazole regioisomer was verified by single-crystal X-ray diffraction analysis. Crystal-structure measurement was successfully carried out on (Z)-1-(4-(4-iodophenyl)-5-(p-tolylimino)-4,5-dihydro-1,3,4-selenadiazol-2-yl)ethan-1-one and (Z)-1-(5-((4-methoxyphenyl)imino)-4-(4-(methylthio)phenyl)-4,5-dihydro-1,3,4-selenadiazol-2-yl)ethan-1-one. Likewise, the (Z)-geometry of the hydrazonoyl chloride reactant was proven by X-ray diffraction studies. As representative examples, crystal-structure determination was carried out on (Z)-2-oxo-N-phenylpropanehydrazonoyl chloride and (Z)-N-(3,5-bis(trifluoromethyl)phenyl)-2-oxopropanehydrazonoyl chloride. Density functional theory calculations at the B3LYP-D4/def2-TZVP level were conducted to support the noted experimental findings and suggested mechanism.

Recent Advances on C-Se Bond-forming Reactions at Low and Room Temperature

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Over the last decades, many methods have been reported for the synthesis of selenium- heterocyclic scaffolds because of their interesting reactivities and applications in the medicinal as well as in the material chemistry. This review describes the recent numerous useful methodologies on C-Se bond formation reactions which were basically carried out at low and room temperature.

A Novel and Convenient Synthesis of 3-Amino-2H-1,2,4-Triazoles from Isoselenocyanates and Hydrazine Hydrate

A novel and convenient one-pot synthesis of 3-amino-2 H-1,2,4-triazoles from two molecules of isoselenocyanates and hydrazine hydrate via cyclodeselenisation was developed. Various 3-amino-2 H-1,2,4-triazoles were obtained in moderate to good yields (33–45%, based on isoselenocyanates). The selenium powder and aromatic amine side products during the reaction could be recycled for efficient preparation of isoselenocyanates, which improved the atom economy. A plausible mechanism was proposed for the formation of the target products.

An Efficient One-Pot Synthesis of 2-Amino-1,3,4-Selenadiazoles

An efficient one-pot synthesis of 2-amino-1,3,4-selenadiazoles from isoselenocyanates, hydrazine hydrate and aromatic aldehydes has been developed. This approach provides a simple, mild and facile way to construct various derivatives in moderate to good yields (57–82%). A plausible mechanism is proposed for the formation of the target products.

Synthesis of Cyanamides from Isoselenocyanates Promoted by Recyclable Ionic Liquid-Supported (Diacetoxyiodo)Benzene

One-pot synthesis of cyanamides from isoselenocyanates through deselenisation promoted by ionic liquid-supported hypervalent iodine(III) reagent 1-(4-diacetoxyiodobenzyl)-3-methylimidazolium tetrafluoroborate ([dibmim]+[BF4]−) was developed. This approach provided a simple, mild and environmentally benign way to construct cyanamides in good yields. Moreover, powder Se and [dibmim]+[BF4]− could be easily recycled. It was the first example of [dibmim]+[BF4]− to be used as a deselenising agent.

Efficient Synthesis of 4h-Benzo[d][1,3]oxazin-4-ones from Anthranilic Acids and Aryl Isoselenocyanates

A synthesis in good to excellent yields of 23 4H-benzo[d][1,3]oxazin-4-ones, 18 of which are novel, from monosubstituted anthranilic acids and variously substituted phenyl isoselenocyanates without using any harsh reagents has been developed. The Se powder precipitated during the reaction could be efficiently recycled for the preparation of the aryl isoselenocyanates.