ABSTRACT2-amino-5-mercapto-1,3,4-thiadiazole 1 was introduced in condensation reaction with terephthaldehyde to yield bis-imine derivative 2. Compound 1 was also converted to the corresponding diazonium salt which was introduced in coupling reactions with alkaline solution of 2-hydroxybenzaldehyde and 4-hydroxybenzaldehyde as coupling reagents to give azo derivatives 4a and 4b containing aldehyde group, respectively. The resulting aldehydes 4a and 4b were then introduced in condensation reactions with 2-amino-5-mercapto-1,3,4-thiadiazole 1 to obtain the imines 5a and 5b respectively. The resulting imines 2, 5a and 5b were treated with both maleic and phthalic anhydrides, respectively, under (2+5) cycloaddition conditions afforded eight new bis-1,3,4-thiadiazoles substituted with 1,3-oxazepine and 1,3-benzoxazepine moieties (3a, 3b) and (6a-d)respectively. The new synthesized thiadiazoles have some biological, pharmaceutical and medicinal applications.

Heterocyclic compounds possess a cyclic structure with two or more different kinds of atoms in the ring. The history of heterocyclic chemistry began in the 1800s, in step with the development of organic chemistry. Since rings can be of any size, from three-membered upwards, and since the heteroatoms can be drawn in almost any combination from a large number of the elements (though nitrogen, oxygen, and sulfur are still by far the most common), the number of possible heterocyclic systems is almost limitless. An enormous number of heterocyclic compounds are known and this number continues to increase very rapidly. This work is divided into two different parts: First part: Synthesis of imines by Schiff base reaction, this part involves synthesis three of imines by treatment isatin with a variety of cyclo primary amines. Second part: [3 + 2] Cycloaddition reaction, this part includes reacting each product of the first part with two types of amino acids. All steps of reactions followed by TLC– papers. All synthesized compounds were confirmed through the use of different spectroscopic techniques (IR and NMR), melting points.

In the current investigation, two series of 2-amino thiazole derivatives were prepared. The first series involved synthesis of (Z)-3-(thiazol-2-ylimino)indolin-2-one (A1) as Schiff base derivatives of 2-amino thiazole and isatin, then synthesis of compounds A5, A6 and A7 as five membered rings (imidazolidins) by using different amino acids, and synthesis of compounds A3 and A4 as seven membered rings (1,3-oxazepine-di-one) by using maleic and phthalic anhydrides respectively. In the second series, 2-amino thiazole was treated with acetyl acetone to form (2E,4E)-N2,N4-di(thiazol-2-yl) pentane-2,4-diimine (A2) as di-Schiff base derivatives, and finally the preparation of imidazolidin (A8) by using 2 mol of tyrosine and preparation of tetrazole derivative (A9) by using 2 mol of sodium azide. The biological study for the above two series indicated that both gram-negative and grampositive activities were noticed.

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