Research On C-s Bond Cleavage And Conversion Reactions Of Benzothiazoles And Sodium Sulfinates

Activated cleavage and transformation reactions of C-S bonds are very important in the petroleum industry and synthetic chemistry. Recently, transitionmetal-catalyzed C-S bond activation and cleavage have been applied in diverse bioorganic and synthetic chemistry. In particular, as cross-coupling has been paid more and more attention in the construction of new chemical bonds, organosulfur compounds have been shown increasing importance as coupling partners or building blocks and have exhibited potentials for biomimetic synthesis. With the rise of green chemistry, using simple materials under mild conditions to achieve selective organic synthesis has been greatly significant in organic chemistry. The development of new methods for environmentally friendly C-C bond and C-hetero bond generation reactions by C-S bond cleavage are described, and the C-S bond cleavage and further conversion of benzothiazoles and sodium sulfinates are studied in this paper. The detailed researches were described as follows:1. A direct arylation of benzothiazoles with aromatic aldehydes has been discovered. The cheap and non-toxic iron catalyst efficiently catalyzed the coupling reactions in good to excellent yields using oxygen as the oxidant under base-free conditions. Various functional groups were well tolerated under the optimized reaction conditions. This method affords a cheap and efficient alternative route for the synthesis of hetero- aromatic biaryls.2. A convenient and efficient method for the synthesis of 2-acylbenzothiazoles from benzothiazoles and aromatic ketones using oxygen as the oxidant is described. Benzothiazole was converted to 2-aminothiophenol via ring-opening reaction in the presence of iron catalyst, and C(sp3)-H bond of acetophenone was activated. 2-Aminothiophenol reacts with activated acetophenone by condensation, cyclization and oxidative dehydrogenation affording the desired product. Solvent played an important role in this transformation.3. A palladium-catalyzed desulfitative hydroarylation of alkynes with aryl sulfinic acid sodium salts is described. Sodium sulfinates have the potential to serve as the ideal aryl source reacting with alkynes through release of SO2. The reaction showed good regio- and stereoselectivity, and afforded the hydroarylation products in good yields.4. An iron-catalyzed sulfenylation and arylation of alkynes with aryl sulfinic acid sodium salts is developed. Aromatic sodium sulfinates acted both as aryl sources and sulfenylation reagents. The C-C and C-S bond forming reactions were realized in one pot using iron as an environmentally benign catalyst. This novel process provides an efficient approach for the synthesis of triarylvinyl sulfides.5. The palladium-catalyzed desulfinative iodination of sodium sulfinates and sulfonyl hydrazides with KI or I2 is described. The reaction proceeds smoothly under mild conditions using O2 or air as an environmentally benign oxidant. Various functional groups were tolerated under the optimized reaction conditions. This kind of reaction is not sensitive to moisture and oxygen and thus is very easy to handle. This method affords an efficient alternative route for producing aryl iodides.