SYNTHESIS AND CHARACTERIZATION OF NOVEL 1,3- OXAZEPANE DERIVATIVES VIA REACTION OF PHENYI SUCCINIC ANHYDRIDE WITH SCHHIF'S BASES

Novel 1,3-oxazepane-4,7-dione derivatives were synthesized by the reaction of phenyl succinic anhydride with Schiff‘s bases in anhydrous benzen with high yields. Schiff ' s bases were synthesized by the reaction of heteroaromatic aldehydes or ketones with primary heterocyclic amines. The resulting products were identified by their melting point and their molecular structures were confirmed by FT-IR , UV-Vis. and 1 HNMR spectroscopy.


Introduction
Schiff's bases are used as substrates in the preparation of a large of bioactive and industrial compounds via ring closure,cyclo addition and replacement reactions .In addition , Schiff bases are well known to have biological activities (1-3) ."Oxazepine" refers to any seven-membered ring Containing an oxygen and nitrogen atom .The 1,3-Oxazepine is a branch of many types of the heterocyclic oxazepine (4-10).The core structure of 1,3-Oxazepane-4,7diones consists of a seven-membered ring along with two carbonyl group.Over the years, the syntheses of oxazepine derivatives have been investigated and documented (11)(12)(13)(14)(15)(16).Oxazepines is used as antibiotics ,enzyme inhibitors pharmacological interst,it has much chemical and biological studied (17)(18)(19).Experimental:-All solvents were distilled and dried on anhydrous CaCl 2 immediately prior to use, and all non-aqueous Reaction were conducted in dried glass ware , the Reflux condenser was equipped with anhydrous CaCl 2 guard tube.Schiff ' s bases and phenyl succinic anhydride were purified before use.Melting points were recorded on Electro thermal Melting Point (Stuart) mode l samp 30 .All FT-IR spectra were recorded at room temperature from 4000cm -1 to 400cm -1 with KBr disce on Shimadzu FT-IR 84005 spectrophotometer and UV-Vis.spectra were recorded at room temperature from 200 nm to 400 nm in absolute ethanol on Shimadzu Double-Beam Spectrophotometer UV-210A .The 1 H-NMR spectra were recorded on Bruker 500 MHz -Avance III spectrometer in DMSO-d6 as a solvent using (ppm) for chemical shift relative to tetra methyl saline (TMS) as an internal standard.

General procedure for synthesis of Schiff's bases (A 1 -10 ).
A mixture of 4-Aminoantipyrine ( 0.001mol) and4-Chlorobenzaldehyde (0.001mol) and trace of glacial acetic acid in absolute ethanol (50ml) was placed in a(100ml) roundbottom flask equipped with condenser and stir bar.The mixture was allowed to react at reflux temperature for 4hr, then allowed to cool down to room temperature , where by a crystalline solid of Schiff's base (A 1 ) separated Out .The solid product was recrystallized twice from ethanol .Other Schiff ' s bases(A 2 -10 ) were synthesized by following the same Procedure .The structural formulas, names, melting points ,colures ,and percentage yields for the synthesized Schiff ' s bases are given in ( table6).General procedure for synthesis of 1,3-Oxazepane-4,7-dione (B 1 -B 10 ).In well dried 100-ml round-bottom flask equipped with condenser and anhydrous calcium chloride tube guard a mixture of Schiff ' s base s (0.002mol) and phenyl succinic anhydride (0.002mol) dissolved in (30ml) of anhydrous benzene ,the reaction mixture was refluxed for (5hr) and left to stand for (24hr) , then solid product of (B 1 ) precipitated.The solid product was filtered off and recrystallized form ethanol .Other derivatives (B 2-10 ) were synthesized following the same procedure .The structural formulas , names , melting points, colures, and percentage yields for the synthesized1,3-Oxazepane-4,7dione are given in (table7) .

Results and Discussion
In this work the synthesis of novel 1,3-Oxazepane -4,7-dione by direct reaction of Schiff ' s bases with phenyl succinic anhydride in anhydrous benzene is reported .Schiff ' s bases were synthesized from the condensation reaction of commercially available heterocyclic aldehydes or ketones with primary heterocyclic amines of very well known mechanism (20).
Formation of the Schiff's bases products were followed up by the disappearance of both (C=O) absorption bands at (1660-1700)cm -1 and (-NH 2 ) absorption bands at (3340-3420cm -1 ) in the FT-IR spectra of the carbonyl compounds and the primary amines respectively, and the appearance of the absorption frequency of azomethene group (C=N) at (1630-1680) cm -1 in the FT-IR spectra of the resulting imines.The UV-Vis.Spectra of these imines show absorption maxima at (202-430 nm) owing to the electronic transfer π π and characteristic of the structures of the synthesized Schiff ' s bases.
The synthesis of novel 1,3-Oxazepane-4,7dione were achieved by the polar cycloaddition reaction of imines to phenyl succinic anhydride fairly anhydrous benzene at reflux condition.
It may be concluded that the reaction takes place via concerted dipolar cycloaddition mechanism as in the following reaction scheme: In the slow step of this mechanism ,the nucleophilic azomethine group attacks the electrophilic carbon atom of the carbonyl group of the anhydride associated to give dipolar reactive intermediate.
Collapse of the reactive intermediate in an intramolcular cycloaddition in a fast step gives the target molecule.
The FT-IR spectra of the products show characteristic absorption band at (1608-1724cm-1 ) indicative of C=O group formation of (lactam/lactone) beside the characteristic bands of the residual groups in the structure, table,(4).