The Norrish type II reaction is an interesting photochemical process through Csp3-H functionalization of N,N-disubstituted oxo-amine or oxo-amide provides access to diverse synthetic building blocks by different pathw...The Norrish type II reaction is an interesting photochemical process through Csp3-H functionalization of N,N-disubstituted oxo-amine or oxo-amide provides access to diverse synthetic building blocks by different pathways.Due to the finite lifetime of the excited state and rapid changes in the intermediates,there are significant challenges in controlling the stereochemical outcomes of this reaction over the strong racemic background reaction.The oxazolidin-4-one skeleton is a useful structural motif found in bioactive molecules,and it is the one that is produced by a not well-studied route among the three routes in Norrish type II cyclization.Herein we report the asymmetric version of this process,and a variety of oxazolidin-4-ones is achieved from arylα-oxoamides via triplet excimers with three H-transfer steps interspersed by a cyclization step under mild,visible light.In the presence of chiral N,N-dioxide/metal complex catalysts,diastereo-and enantiocontrol in this photochemical reaction happens with enantioselective protonation of enol intermediates as the crucial stereo-determining step,getting the better of the thermodynamical control pathway.Trans-oxazolidine-4-ones can be obtained in high enantioselectivity,which can be transferred into optically active cis-oxazolidine-4-ones after the treatment with a base.展开更多
以二环[3,1,0]己烷为骨架设计前列腺素光化学前体的反应路线,经过10步反应合成了具有NorrishⅡ型光化学特点的光化学反应前体目标产物.通过MS、HPLC、1 H NMR、13C NMR和DEPT 135等手段的表征了该化合物的一维结构,并且利用二维核磁共...以二环[3,1,0]己烷为骨架设计前列腺素光化学前体的反应路线,经过10步反应合成了具有NorrishⅡ型光化学特点的光化学反应前体目标产物.通过MS、HPLC、1 H NMR、13C NMR和DEPT 135等手段的表征了该化合物的一维结构,并且利用二维核磁共振技术1 H-1 H COSY、HSQC、HMBC、ROESY和NOE等手段对所合成目标产物的二维结构物进行了测定,确定了目标产物的空间结构.展开更多
The density functional theory（DFT） calculations were performed to investigate a typical Norrish/Yang type II photoreaction of 5-methylbicyclo[1.1.1]-pentanyl ketone.The results reveal the essential correlation betwe...The density functional theory（DFT） calculations were performed to investigate a typical Norrish/Yang type II photoreaction of 5-methylbicyclo[1.1.1]-pentanyl ketone.The results reveal the essential correlation between structures on the one hand and energies,on the other hand,of the reactants,transition states and products based on both singlet ground（S0） and triplet excited（T1） potential energy surfaces.The feasible mechanism indicates that an intramolecular Norrish/Yang cyclization reaction takes place via H-abstraction to obtain the sole chiral cyclobutanol photoproduct.The located crossing point plays an important role in the cyclization process,which permits intersystem crossing（ISC） from T1 to S0 state.The rate-determining step may be to experience ISC between two different potential energy surfaces,requiring sufficient time for electron spin reversion,i.e.,spin multiplicity alteration.These conclusions are further confirmed by the second-order M ller-Plesset perturbation theory（MP2） calculations.展开更多
The first example of the p-orbital overlap controlled enantioselectivity of Norrish type II photocyclization reaction was described. Irradiation of 5-methyl bicyclo[l. 1.1 ]pentanyl ketone with UV in the solid state a...The first example of the p-orbital overlap controlled enantioselectivity of Norrish type II photocyclization reaction was described. Irradiation of 5-methyl bicyclo[l. 1.1 ]pentanyl ketone with UV in the solid state as well as in the acetonitrile solution afforded the Norrish/Yang photocyclization compound as the sole product. Solid-state asymmetric photochemical studies using ionic chiral auxiliary technique led to the enantioselectivity as high as 60%. The results were rationalized by Xray single crystal structure.展开更多
The photochemical behavior of bicyclo[2.1.1]hexyl derivatives was investigated by irradiation with a 450 W medium-pressure mercury lamp in acetonitrile solution.The irradiation of methyl bicyclo[2.1.1]hexane-5-carbony...The photochemical behavior of bicyclo[2.1.1]hexyl derivatives was investigated by irradiation with a 450 W medium-pressure mercury lamp in acetonitrile solution.The irradiation of methyl bicyclo[2.1.1]hexane-5-carbonylbenzoate(1a)led to both Norrish type II cyclization and cleavage products with a molar ratio of 1∶2.2,whereas the irradiation of methyl 5-methylbicyclo[2.1.1]hexane-5-carbonylbenzoate(1b)afforded the only Norrish/Yang photocyclization compound as the sole product.Such results were illustrated by several geometric parameters for Norrish/Yang photoreaction asφ_(1),φ_(4) andβobtained from the crystal structures.Furthermore,asymmetric pho-tochemical studies using ionic chiral auxiliary technique were also conducted in the solid state.展开更多
基金the financial support of the National Natural Science Foundation(grant no.22188101)the Science and Technology Department of Sichuan Province(grant no.2021YJ0561)Sichuan University(grant no.2020SCUNL204)for financial support.
文摘The Norrish type II reaction is an interesting photochemical process through Csp3-H functionalization of N,N-disubstituted oxo-amine or oxo-amide provides access to diverse synthetic building blocks by different pathways.Due to the finite lifetime of the excited state and rapid changes in the intermediates,there are significant challenges in controlling the stereochemical outcomes of this reaction over the strong racemic background reaction.The oxazolidin-4-one skeleton is a useful structural motif found in bioactive molecules,and it is the one that is produced by a not well-studied route among the three routes in Norrish type II cyclization.Herein we report the asymmetric version of this process,and a variety of oxazolidin-4-ones is achieved from arylα-oxoamides via triplet excimers with three H-transfer steps interspersed by a cyclization step under mild,visible light.In the presence of chiral N,N-dioxide/metal complex catalysts,diastereo-and enantiocontrol in this photochemical reaction happens with enantioselective protonation of enol intermediates as the crucial stereo-determining step,getting the better of the thermodynamical control pathway.Trans-oxazolidine-4-ones can be obtained in high enantioselectivity,which can be transferred into optically active cis-oxazolidine-4-ones after the treatment with a base.
文摘以二环[3,1,0]己烷为骨架设计前列腺素光化学前体的反应路线,经过10步反应合成了具有NorrishⅡ型光化学特点的光化学反应前体目标产物.通过MS、HPLC、1 H NMR、13C NMR和DEPT 135等手段的表征了该化合物的一维结构,并且利用二维核磁共振技术1 H-1 H COSY、HSQC、HMBC、ROESY和NOE等手段对所合成目标产物的二维结构物进行了测定,确定了目标产物的空间结构.
基金Supported by the National Natural Science Foundation of China(No.20904007)
文摘The density functional theory（DFT） calculations were performed to investigate a typical Norrish/Yang type II photoreaction of 5-methylbicyclo[1.1.1]-pentanyl ketone.The results reveal the essential correlation between structures on the one hand and energies,on the other hand,of the reactants,transition states and products based on both singlet ground（S0） and triplet excited（T1） potential energy surfaces.The feasible mechanism indicates that an intramolecular Norrish/Yang cyclization reaction takes place via H-abstraction to obtain the sole chiral cyclobutanol photoproduct.The located crossing point plays an important role in the cyclization process,which permits intersystem crossing（ISC） from T1 to S0 state.The rate-determining step may be to experience ISC between two different potential energy surfaces,requiring sufficient time for electron spin reversion,i.e.,spin multiplicity alteration.These conclusions are further confirmed by the second-order M ller-Plesset perturbation theory（MP2） calculations.
基金We are grateful to the financial supports from the National Natural Science Foundation of China （Nos. 20802013, 21002018, 21072038）, the Natural Scientific Research Innovation Foundation in Harbin institute of Technology （Nos. 01107866, 01107986） and the Wenzhou Science and Technology Program （No. G20100056）.
文摘The first example of the p-orbital overlap controlled enantioselectivity of Norrish type II photocyclization reaction was described. Irradiation of 5-methyl bicyclo[l. 1.1 ]pentanyl ketone with UV in the solid state as well as in the acetonitrile solution afforded the Norrish/Yang photocyclization compound as the sole product. Solid-state asymmetric photochemical studies using ionic chiral auxiliary technique led to the enantioselectivity as high as 60%. The results were rationalized by Xray single crystal structure.
基金We are grateful for the financial supports from the National Natural Science Foundation of China(Nos.21372055 and 21272047)the State Key Laboratory of Urban Water Resource and Environment(SKLUWRE)(No.2012DX10)+1 种基金the Fundamental Research Funds for the Central Universities(No.HIT.BRETIV.201310)the Zhejiang Natural Science Foundation(No.LY12B02009).
文摘The photochemical behavior of bicyclo[2.1.1]hexyl derivatives was investigated by irradiation with a 450 W medium-pressure mercury lamp in acetonitrile solution.The irradiation of methyl bicyclo[2.1.1]hexane-5-carbonylbenzoate(1a)led to both Norrish type II cyclization and cleavage products with a molar ratio of 1∶2.2,whereas the irradiation of methyl 5-methylbicyclo[2.1.1]hexane-5-carbonylbenzoate(1b)afforded the only Norrish/Yang photocyclization compound as the sole product.Such results were illustrated by several geometric parameters for Norrish/Yang photoreaction asφ_(1),φ_(4) andβobtained from the crystal structures.Furthermore,asymmetric pho-tochemical studies using ionic chiral auxiliary technique were also conducted in the solid state.
