Synthesis Of Sulfur-containing Heterocyclic Compounds With Elemental Sulfur As Sulfur Source

Nitrogen-containing heterocyclic compounds are widely distributed in drugs and natural products due to their unique biological activities.Specially,N,S-containing heterocyclic compounds are rich in pharmacological activities.Thiazole and thiazine have antipsychotic,antitumor,antibacterial,antifungal and other activities.Benzothiazole derivatives are also often found in many biologically active products.At present,it is still of great significance in organic synthesis to construct nitrogen and sulfur-containing heterocyclic compounds by using readily available raw materials without transition metal catalysis.In this thesis,a series of 2-substituted benzothiazole,multi-substituted thiazole and 1,4-benzothiazine compounds were constructed using simple compounds with elemental sulfur as the sulfur source under metal-free conditions.These researchs provide a new environmentally friendly way to construct N,S-heterocycles.The main contents are as follows:1.A novel method for the synthesis of 2-substituted benzothiazoles from aromatic amines,elemental sulfur and arylacetylene or styrene under metal-free conditions has been developed.Among them,ammonium iodide is used as an additive,elemental sulfur is used as a sulfur source and an effective oxidant,which provides a simple method for preparing 2-substituted benzothiazole from readily available starting materials.2.Developed a reaction system for synthesizing polysubstituted thiazole from simple chemical substances.Cheap and easily available ketones,aldehydes,ammonium salts and elemental sulfur react to obtain different polysubstituted thiazoles in medium to good yields under metal-free conditions,providing a new and efficient way to synthesize polysubstituted thiazoles.3.An iodide-catalyzed aerobic [3+2+1] cyclization method was developed for the synthesis of 1,4-benzothiazine.Aniline,acetophenone,and elemental sulfur are used as raw materials,cheap and abundant oxygen is used as a green oxidant,which provides a simple way for the synthesis of 1,4-benzothiazine.