Synthesis And Agricultural Biological Activity Of Functional Molecules Containing Chiral Thiopyran Skeleto

Sulfur-containing heterocyclic compounds,such as thiochromenes,thiochromanes and their derivatives,are widely found in drugs,pesticides and natural products.Therefore,methods for preparing sulfur-containing molecules continue to receive considerable attentions.Thiols（including thiophenol）were selected as the sulfur source to prepare sulfur-containing compounds in previous works.Despite of the impressive progress,bad smelling toxicity,and high reactivity of thiols are still considered as two major challenges in the reactions.N-Heterocyclic carbenes（NHC）as efficient organic catalysts have found impressive success in the construction of sulfur containing heterocyclic compounds.Here we reported an NHC-catalyzed construction of thiochromene derivatives with good yields and high optical purities by using disulfides as thiophenol precursors.Further studies on the bioactivities of chiral thiochromene derivatives obtained from our method for agricultural applications were conducted.The main works for this article are summarized as follows:1.NHC-Catalyzed access to thiochromene derivatives:2,2’-Dithiodibenzaldehyde,which is more stable and environmentally friendly was selected as the sulfur nucleophilic precursor to react with bromoenal under the NHC catalysis.With the insitu reduction and slowly release strategy of the reductant PPh₃ on the disulfide bond,thiophenol could be slowly generated to participate in the catalytic reaction to obtain target molecules.After optimization experiments,chiral thiochromene derivatives were obtained with good yields and high optical purities.Thirty-five chiral thiochromene derivatives have been successfully synthesized.Water has also been found to play a key role in the hydrolysis of thiosulfate and further slowly release thiophenol to participate in the reaction,which obviously improved the yield of the desired product.2.Preliminary biological activity testing of chiral thiochromene derivatives:The chiral thiochromene derivatives obtained from our method were tested on the turbidimetric test at 100 and 50μg/mL of the in vitro antibacterial activity against Xanthomonas axonopodis pv.citri（Xac）.The results showed that all the tested compounds exhibited certain antibacterial activity.In the turbidimetric test at 100 and50μg/mL of the in vitro antibacterial activity,compounds 3b,3n,3s,and 3t have high activity which were better than thiodiazole copper（TC）,with the highest inhibition rate of 87.82%（3t,100μg/mL）and 62.84%（3t,50μg/mL）.Furthermore,the antifungal activity of target compounds was tested via the mycelial growth rate method against two phytopathogenic fungal strains including Phytophthora capsici,Colletotrichum fructicola.The results of mycelial growth inhibition method showed that target compounds demonstrated poor antifungal activity.