Study On The Transition Metal Catalyzed Synthsis Of Aryl Sulfides And Benzimidazoles

Aryl sulfides and benzimidazoles are important compounds in organic chemistry and their preparation has attracted much attention. This thesis includes two parts:(1) Several C-S coupling methods for the syntheis of aryl sulfides; (2) A two-step one-pot syntheis of functionalized benzimidazoles. The research results are summarized as follows:1. C-S cross coupling reaction between aryl iodides and thiols catalyzed by CuI under ligand free condition has been developed. We tried the reactions in DMSO,PEG or PEG-H2O respectively. The PEG-CuI system coupled aryl iodides with both thiophenols and alkanethiols effectively, which brings significant improvement compared to the literature ligand free methods. The PEG-CuI system could be reused for 6 times without loss of catalytic ability.2. C-S coupling reaction between aryl iodides and thiols catalyzed by Pd/C under ligand free condition by using KOH as the base and DMSO as the solvent has been developed. This catalytic system coupled aryl iodides with thiophenols effectively. But it is not so effective with alkanethiols. The catalyst could be Recovered and reused for 6 times with out loss of catalytic ability.3. A rapid and direct C-S coupling between aryl halides and thiols has been developed in good to high yields catalyzed by strong base without a transition-metal catalyst. The method is effective for both aryl iodides,bromides and cholorides. A mechanism via the benzyne intermediate has been proposed.4. One-Pot Synthesis of Functionalized Benzimidazoles via Cascade Reactions of o-Aminoanilines with Alkynes and p-Tolylsulfonyl Azide has been developed. 1H-Pyrimidines could also be synthesized by using Naphthalene-1,8-diamine as substrate. The protocol is valuable for its efficient and general as well as the starting materials are commercially available or readily prepared.