.2 H-1, 2,3 - Two Nitrogen And Phosphorus Heterocyclic Of Glutaric Vinyl Synthesis And Reactivity Studies

Two-coordinated trivalent phosphorous compounds have been known for about forty years. In this regard, 2H-1,2,3-diazaphospholes (DAP (II)), which were firstly synthesized by treatment of ketone hydrazones bearing active a-hydrogen atoms with phosphorus trichloride in 1967 by Ignatova and his coworker, have earned much attention due to their easy availability and diverse reactivity. Since then, considerable efforts have been devoted to the study of novel two-coordinated trivalent phosphorous compounds. Considering the fact that anellated heterophospholes have been at the forefront of the search for novel phosphor-containing fused heterocycles, we have initiated a program of study on the synthesis and reactions of novel 2H-1,2,3 -diazaphospholes.In the first part of the present work, the precedent methods for the synthesis of 2H-1,2,3-diazaphospholes have been improved. Our synthetic procedure was proved to be more reliable. A range of diversely substituted 2H-1,2,3-diazaphosphoes were accessible starting from ketone hydrazones. The crude intermediates 2-acyl-3-chloro-3,4-dihydro-2H-1,2,3 -diazaphospholes, generated by sequentially treating hydrazones with phosphorus trichloride, filtering off the formed salt of NEt₃·HCl and evaporating the solvent and the excess PCl₃, were directly taken into anhydrous benzene and subjected to further elimination of HCl with triethylamine. Using this modified procedure, we were able to synthesize diversely substituted compounds 3a-3h in moderate to acceptable yields. The structural characterization has principally been performed by means of spectral analysis, including IR, ¹H NMR, ¹³C NMR, ³¹P NMR, MS, HRMS.Aside from the above work, we have also tried much efforts to explore a synthetic way to novel trifluoromethyl-containing 2H-1,2,3-diazaphosphoes. But, the investigation was unsuccessful.The Diels-Alder reaction is of no doubt among the most widely used synthetic strategies for the construction of six-membered cyclic compounds. The incorporation of heteroatoms in the diene and/or dienophile moieties offers also a powerful synthetic way to six-membered heterocycles. Acting as an excellent dienophile, the >C=P- functionality in 2-acetyl-2H-1,2,3-diazaphosphoes was found to undergo smooth Diels-Alder reaction with cyclopentadiene stereospecifically, leading to novel 4,7-methanophosphorino[1,2-c][1,2,3]diazaphosphols 10a-10d'. Both the endo andexo adducts can be obtained by varying the reaction conditions. In a similar manner, the D-A reaction of 2-acetyl-2H-1,2,3-diazaphosphoes and furan was found to proceed smoothly, resulting in the formation of the respective cycloadducts 12a-12c. However, the stereospecificity seems to be low and a mixture of endo and oxo products have not been isolated in all cases.On the other hand, 1,3-dipolar cycloaddition has become extraordinarily versatile method for assembly of five-membered heterocycles. Our results demonstrated that 2H-1,2,3-diazaphospholes can serve as satisfactory 1,3-dipolarophiles. In the present thesis, the reaction of 2H-1,2,3-diazaphospholes with a range of common 1,3-dipoles has been performed. The tested 1,3-dipole molecules include two diazoalkane compounds, namely 9-diazofluorene and diphenyldiazomethane, diazoone and arylnitrile oxides. The product type of 2H-1,2,3-diazaphospholes and 9-diazofluorene varied with the polarity of solvent and the substituent in 2H-1,2,3-diazaphospholes. The reaction proceeded via a 1,3-dipolar cycloaddition mechanism, leading to either the spiro phosphadiazabicyclohexenes 16a-16e. after loss of nitrogen or the cyclic trimers 18a-18e. In one case, the initially formed adduct phosphatetraazabicyclooctadiene 17 has been isolated. For the reaction of 2H-1,2,3 -diazaphospholes and diphenyldiazomethane, all the initial [3+2] adducts were thermally unstable and not isolated. They react further by loss of nitrogen, giving out cleanly the bicyclic compounds 22a-22h. However, α-diazo carbonyl compounds are unstable and the expected cycloaddition products with 2H-1,2,3 -diazaphospholes were contaminated by considerable amounts of byproducts, therefore, isolation and purification were not attempted. 2-Acetyl-5-methyl-2H-1,2,3-diazaphosphole reacted with 4-chlorobenzoyl chloride oxime at room temperature yielding the [2+3] cyclic addition product 28 regiospecifically. Thus, the cycloaddition of 2H-1,2,3-diazaphospholes and 9-diazofluorene, diphenyldiazomethane, and nitrile oxides provides a mild, high yielding and easy handling method to novel annelated phosphole heterocycles.