| Lots of drugs and natural products contain the basic framework of the multi-substituted alkenyl.How to construct the multi-substituted alkenes with high stereo-and region-selectivity has been a research hotspot in organic chemistry.At present,there are some shortcomings in the preparation of tetra-substituted olefins,such as harsh conditions,poor selectivity,complex by-products and poor yield.Therefore,it is of great theoretical and practical significance to develop an efficient,highly stereo-and region-selective method for the synthesis of these multi-substituted alkenes.Vinylic chalcogenides can be used as important intermediates for the synthesis of multi-substituted alkenes,because the C-Z(S,Se,Te)bonds of these vinylic chalcogenides can be easy to converte to new C-C bonds.At present,some methods for the synthesis of vinylic chalcogenides have been reported,but there are some shortcomings,such as poor selectivity,harsh reaction conditions and poor yields.In our previous works,we have developed efficient methods for the highly stereo-and regio-selective construction of symmetry vinylic chalcogenides with the same C-Z(S,Se)bonds catalyzed by cesium hydroxide.According to the literatures,different C-Z(S,Se,Te)bonds have different reactivity,which can be cleaved selectively by modulating the reaction conditions.Therefor,asymmetric vinylic chalcogenides containing two different C-Z(S,Se,Te)bonds can be used as important platform molecules for the high regio-and stereo-selective construction of multi-substituted alkenes.And the organic chalgogenide species can be oxidated to diaryl disulfides(diselenides or ditellurides),which can be used to synthesize vinylic chalcogenides,realizing the recycle of chalcogen resource.On the basis of above analysis,we wish to develop a high regio-and stereo-selective method for the synthesis of asymmetric vinylic chalcogenides via a one-pot reaction of terminal alkynes with a binary system of ArSSAr/ArSeSeAr or ArSSAr/ArTeTeAr catalyzed by cesium hydroxide.The application of these asymmetric vinylic chalcogenides in the construction of multi-substituted alkenes will be also study in this paper.Some innovative results and conclusions were listed as follows:(1)A high stereo-and regio-selective method for the synthesis of(Z)-1-arylseleno-2-arylthio alkenes was developed via a one-pot thioselenation of alkynes with a binary system of ArSSAr/ArSeSeAr catalyzed by cesium hydroxide.The influences of catalysts,reaction time,solvent,temperature and amount of catalyst to the reaction were investigated by using the thioselenation of propargyl alcohol with a binary system of PhSSPh/PhSeSePh as a model reaction.The scope of the thioselenation was investigated under optimized conditions and a series of(Z)-1-arylseleno-2-arylthio alkenes were obtained with yields up to 92%.The structures of all desired products were characterized and confirmed by]H NMR,13C NMR,MS and HRMS,and the Z configurations of the desired products were confirmed by NOESY and X-ray experiments.The mechanism of the reaction was systematically studied by controlling experiments,and theoretical calculations,and a proposal mechanism was brought forward.The(Z)-1-aryl seleno-2-arylthio alkenes were used as platform molecules for the high stereo-and region-selective synthesis of tetra-substituted olefins.(2)A high stereo-and regio-selective method for the synthesis of(Z)-1-aryltelluro-2-arylthio alkenes was developed via a one-pot thiotelluration of alkynes with a binary system of ArSSAr/ArTeTeAr catalyzed by cesium hydroxide.Under the optimized conditions obtained in last part,the scope of the thiotelluration was investigated,and a series of(Z)-1-aryltelluro-2-arylthio alkenes were synthesized with yields up to 95%.The structures of all desired products were characterized and confirmed by 1H NMR,13C NMR,MS and HRMS,and the Z configurations of the desired products were confirmed by NOESY experiment.The(Z)-1-aryltelluro-2-arylthio alkenes were used as platform molecules for the high stereo-and region-selective synthesis of tetra-substituted olefins,which provides an effective and universal method for the preparation of multi-substituted olefins(3)This part,we use NiF2 as catalyst to explore the coupling reaction of(Z)-1,2-diaryl(alkyl)thio alkenes with Grignard reagents.The effects of different catalysts,ligands and their dosage,solvents and reaction time on the reaction were investigated by using the reaction of(Z)-1,2-diphenyl thiostyrene with methyl magnesium chloride as the model reaction and the optimal conditions were obtained.The scope of the reaction was investigated under the optimized conditions,and a series of(Z)-1-alkyl(aryl)-2-aryl(alkyl)thio alkenes were obtained with yields up to 95%.The structures of all desired products were characterized and confirmed by 1H NMR,13C NMR,MS and HRMS,and the Z configurations of the desired products were confirmed by NOESY.The mechanism of the reaction was systematically studied by controlling experiments and NMR tracking experiments,and a proposal mechanism was brought forward.(Z)-Tamoxifen was successfully prepared by using one of(Z)-vinylic sulfides as starting material with high purity.And the organic chalgogenide species ArSH can be oxidated to diaryl disulfides,which can be used to synthesize vinylic chalcogenides,realizing the recycle of chalcogen resource.(4)In this part,we study the synthesis of multi-substituted naphthalene via the reaction of diarylacetylenes with Grignard reagents catalyzed by NiCl2.The effects of solvents,time,temperature,different additives,catalysts and their dosage on the reaction were investigated by using the reaction of diphenylacetylene and phenyl magnesium bromide as model reaction,and the optimal conditions were obtained.The scope of the reaction was investigated under the optimized conditions,and a series of tetra-substituted naphthalenes were obtained with yields up to 84%.The structures of all desired products were characterized and confirmed by 1H NMR,13C NMR,MS.This method provides a simple and effective way for the synthesis of multi-substituted naphthalene. |
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