The Synthesis of Some New Fused and Substituted Chromenes

Some new chromeno[2,3-b]pyrimidines, chromeno[3,2-c]pyridines, chromeno[2,3-b]pyridines and 3-chromenyl-1,3-thiazines were synthesized via the synthetic studies of the reaction of 2-imino-2H-chromen-3-thiocarboxamide with some aromatic aldehydes, active nitriles, and their ylidene derivatives.     

KINETICS AND MECHANISM OF THE REACTION BETWEEN OLIGOSILOXANES AND P-TRICHLORO-N-DICHLOROPHOSPHORYL MONOPHOSPHAZENE (Cl3P[dbnd]N-POCl2)

Abstract

³¹P NMR investigation has been made of the action of Cl₃P[dbnd]N-POCl₂(I) first on hexamethyldisiloxane (Me₃Si)₂O and then on oligosiloxanes Me₃Si-(OSiMe₂)_n-OSiMe₃ n = 2 and n=3. The reactions were carried out in bulk or in solution with molar ratios siloxane/(I) varying from I to 5. It was demonstrated that only the monosubstitution of a chlorine atom by the -(OSiMe₂)_n,-OSiMe₃ species n = 0, 2, 3 with elimination of trimethylchlorosilane occurred leading to the derivatives Cl₂OP-N[dbnd]PCl₂O(SiMe₂-O)_nSiMe₃ (II). For n=2, 3 the siloxane redistribution reactions were observed by ²⁹Si NMR analysis. A two steps mechanism is proposed. consisting in a nucleophilic substitution, involving a tricoordinate phosphazenium intermediate, followed by the formation of an active ionic centre probably an oxonium ion, arising from the solvatation by the siloxane of this phosphazeniurn ion and /or of (II) leading to the redistribution reactions. The influences of the solvent, of trimethylchlorosilane, of the temperature, and of the addition of a protonated species (MDH) were investigated.     

Synthesis of Triazolyl-Oxadiazolyl-Thiazolyl- and Thiadiazolylbenzofuran of Potential Biological Activity

4,7-Dimethoxy ( Ia ) and 4-methoxy ( Ib ) 6-hydroxybenzofuran-5-carbohydrazide were reacted with aryl or alkyl isothiocyanates to give the corresponding thiosemicarbazides ( IIa-h ). Cyclization of the substituted thiosemicarbazides with sodium hydroxide led to the formation of 1,3,4-triazol-2-yl-benzofuran derivatives ( IIIa-d ). Desulfurization of thiosemicarbazide by mercuric oxide gave 1,3,4-oxadiazolyl-benzofuran ( IVa-c ). Treatment of thiosemicarbazide with ethyl bromo-acetate or f -bromopropionic acid yielded 4-thiazolidin-2-yl-carbonyl-benzofuran ( Va-h ). The reaction of compounds IIb , e , f with sulphuric acid or phosphorus oxychloride gave 1,3,4-thiadiazol-2-yl-benzofuran ( VIa-d , VII ).     

Transferred multipolar atom model for 10β,17β‐dihydroxy‐17α‐methylestr‐4‐en‐3‐one dihydrate obtained from the biotransformation of methyloestrenolone

Biotransformation is the structural modification of compounds using enzymes as the catalysts and it plays a key role in the synthesis of pharmaceutically important compounds. 10β,17β‐Dihydroxy‐17α‐methylestr‐4‐en‐3‐one dihydrate, C₁₉H₂₈O₃·2H₂O, was obtained from the fungal biotransformation of methyloestrenolone. The structure was refined using the classical independent atom model (IAM) and a transferred multipolar atom model using the ELMAM2 database. The results from the two refinements have been compared. The ELMAM2 refinement has been found to be superior in terms of the refinement statistics. It has been shown that certain electron‐density‐derived properties can be calculated on the basis of the transferred parameters for crystals which diffract to ordinary resolution.     

Densitometric Kinetic Stability Studies of Some Plant Extracts Using Different Regression Methods

JPC – Journal of Planar Chromatography – Modern TLC -