Intramolecular amidation: synthesis of novel imidazo[2,1-b][1,3,4]thiadiazole and imidazo[2,1-b][1,3]thiazole fused diazepinones

Novel heterocyclic systems 2-alkyl/aryl-9-(2-hydroxybenzylidene)-7,9-dihydro-8H-[1,3,4]thiadiazolo[2′,3′:2,3]imidazo[4,5-d][1,2]diazepin-8-one and 9-(2-hydroxy-benzylidene)-3,3-dimethyl-3,4,7,9-tetrahydro-2H-11-thia-4b,6,7,10-tetraazaindeno[1,2-a]azulene-1,8-dione are synthesized via an intramolecular amidation reaction. An interesting ring opening and cyclization of 2-alkyl/aryl-6-(2-oxo-2H-chromen-3-yl)imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde and 6,6-dimethyl-8-oxo-2-(2-oxo-2H-chromen-3-yl)-5,6,7,8-tetrahydroimidazo[2,1-b][1,3]benzothiazole-3-carbaldehyde are discussed.     

Novel Pyridazine Fused Heterocyclic System: A New Route for the Synthesis of 2‐Alkyl/Aryl[1,3,4]Thiadiazole[2′,3′:2,3] Imidazo[4,5‐d]Pyridazin‐8(7H)‐One

A series of novel imidazo[2,1‐b][1,3,4]thiadiazole fused pyridazinones have been synthesized in moderate yields by the reaction of 2‐alkyl/arylimidazo[2,1‐b] [1,3,4]thiadiazole‐6‐carbohydrazides under Vilsmeier–Haack reaction conditions. This simple methodology has utility for the synthesis of various fused heterocyclic systems.     

Synthesis,spectroscopic and crystal structure analysis of a compound with pharmocophoric substituent: 2-cyclohexyl-6-(2-oxo-2H-chromen-3-yl)- imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde

Imidazo[2,1-b][1,3,4] thiadiazole derivatives are significant for their various pharmacological properties. This paper reports the synthesis and structure of one of them, 2-cyclohexyl-6-(2-oxo-2H-chromen-3-yl)imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde. The compound crystallizes in the monoclinic space group P2₁/c with a=17.316(3)?, b=6.5420(9)?, c =17.056(3)?, β=112.909(2)°, V=1779.7(4)?³, z=4. The, Imidazo[2,1-b][1,3,4] thiadiazole and the coumarin ring systems are each planar but inclined at an angle of 48.14(2)° towards each other. The crystal structure is stabilized by C–H … O interactions.     

Synthesis,Spectroscopic and Crystal Structure Analysis of <Emphasis Type="Italic">N</Emphasis>-[imidazolidin-2-ylidene]-5-(thien-2-yl)[1,3,4]thiadiazole-2-amine

The crystal structure of the title compound has been determined. The compound crystallizes in the monoclinic space group P2₁/c with a = 5.9885(2) Å, b = 14.7345(4) Å, c = 12.3719(4) Å, β = 96.655(5)°, V = 1084.31(8) Å³, z = 4. An intramolecular N–H···N hydrogen bond forms a pseudo-six-membered ring with graph set S ¹ ₁(6). The crystal structure is stabilized by intermolecular interactions of the type N–H···N and C–H···N. The packing motifs in accordance with Etter’s analysis are R ² ₂(8) corresponding to N–H···N dimer and that generated by the chain is C(7).     

Radiation-induced defects in Pr3+-activated Liyf4 laser host

Rare earth doped fluorides have been used in laser applications. Not much is known about the effect of ionizing radiation on the lasing and other properties of fluorides. Therefore, in recent years much attention has been paid to the study of radiation-induced defects in laser materials, as they affect the optical and stimulated emission properties. The defect formation by γ-ray irradiation in Pr³⁺ activated LiYF₄, powder prepared by melt method, have been studied by thermoluminescence and electron spin resonance techniques and are reported in this paper. It is shown that LiYF₄:Pr³⁺ is sensitive to γ-ray radiation. Characterization of this laser material using ESR and photoluminescence techniques is also described.     

Synthesis of Ethyl 8‐Aryl‐8‐hydroxy‐3‐oxo‐8H[1,2,4]oxadiazolo‐[3,4‐c][1,4]thiazine‐5‐carboxylates by Ring‐Expansion Rearrangement

The title compounds were prepared by the ring–ring interconversion of ethyl 5‐nitroso‐6‐arylimidazo[2,1‐b]thiazole‐3‐carboxylates with hydrochloric acid. The effect of electron‐withdrawing substituent in the thiazole ring on the general applicability of the ring–ring interconversion has been also evaluated.     

Intramolecular Amidation: Synthesis of Novel Thiazole‐Fused Diazepinones

A new class of thiazole‐fused diazepinones has been synthesized by the application of intramolecular hydrazonolysis, wherein 2‐arylamino‐4‐coumarinyl‐5‐formyl thiazoles were treated with hydrazine hydrate in refluxing ethanol to yield the rearranged products via an interesting ring‐opening and cyclization process.     

Junjappa–Ila (JI) Heteroaromatic Annulation: A New General α‐Oxoketene Dithioacetals Mediated Inverse Method for Synthesis of Substituted Benzothiazoles

3‐(Methylthio)‐5‐oxo‐2‐(2‐phenyl‐1,3‐thiazol‐4‐yl)‐4,5‐substituted‐pent‐2‐enenitriles 3a–j were obtained in good yields by condensation of (2‐phenyl‐1,3‐thiazol‐4‐yl)‐acetonitrile (1) with various α‐oxoketene dithioacetals 2a–j in the presence of sodium hydride. The intermediates 3a–j underwent smooth cyclization in the presence of PTSA to afford the corresponding benzothiazoles 4a–j in moderate yields.     

Vibrational Studies of Bis(thiourea) Cadmium Chloride and Tris(thiourea) Zinc Sulphate Semiorganic Non-linear Optical Crystals

Single crystals of Bis(thiourea) cadmium chloride (BTCC), and Tris(thiourea) zinc sulphate (TZnS) have been grown from saturated aqueous solution by slow evaporation method at room temperature. The laser Raman and FT-IR spectra on these crystals are recorded in the frequency range 50–4000 cm⁻¹. The spectral data of BTCC and TZnS are interpreted on the basis of thiourea crystal vibrational data. The vibrational frequencies in the FT-IR and Raman spectra of BTCC and TZnS establish that ZnSO₄ and CdCl₂ metal complex are coordinated with thiourea by the metal to sulfur bonds. The effect of the metal complexation on thiourea molecule and nature of bands due to different vibrational modes have been discussed. The lattice vibrational frequencies changes have also been observed and analyzed.