Spirotetramat metabolizes to its active enol form in the plant. We described here a photocaged pesticide delivery system that can release insecticidal spirotetramat enol form upon light irradiation. Covalently linking...Spirotetramat metabolizes to its active enol form in the plant. We described here a photocaged pesticide delivery system that can release insecticidal spirotetramat enol form upon light irradiation. Covalently linking spirotetramat-enol with photoresponsive coumarin generated the caged insecticide. The photophysical and photochemical properties, deprotection photolysis and insecticidal activities of the caged spirotetramat enol were studied. This light-triggered system can undergo cleavage to release free spirotetramat enol form at the presence of blue light （420 nm） or sunlight, Bioassays indicated that the triggered molecule has no obvious insecticidal activity against Aphis craccivora Koch at dark and could be activated by light to release the insecticidal ingredients, which provides precise control over insecticide delivery.展开更多
Keto-enol tautomers of curcumin were confirmed by reversed-phase liquid chromatography（RPLC）/ hybrid quadrupole ion trap/time-of-flight mass spectrometry（QIT/TOFMS）.Tautomers gave different MS/MS spectra in negati...Keto-enol tautomers of curcumin were confirmed by reversed-phase liquid chromatography（RPLC）/ hybrid quadrupole ion trap/time-of-flight mass spectrometry（QIT/TOFMS）.Tautomers gave different MS/MS spectra in negative mode.Different mass spectra were also obtained by hydrogen/deuterium exchange LC/MS/MS in positive mode.Our results suggest that enol form is the major form in the solution（water/acetonitrile）.展开更多
A domino reaction of anilines with cyclic and acyclic enol ethers induced by catalytic amounts of TBPA^（·＋）（5 mol%） was investigated and a series of 2,4-disubstituted-1,2,3,4-tetrahydroquinolines were synthe...A domino reaction of anilines with cyclic and acyclic enol ethers induced by catalytic amounts of TBPA^（·＋）（5 mol%） was investigated and a series of 2,4-disubstituted-1,2,3,4-tetrahydroquinolines were synthesized.Different from cyclic enol ethers, when acyclic enol ethers were used in the reaction,they serve as surrogates of acetaldehyde,producing a series of 2-methyl-4- anilino-1,2,3,4-tetrahydroquinolines.A single electron transfer mechanism was proposed to rationalize the products formation.展开更多
The nucleophilic addition of Ti(IV) enolate derived from methyl aryl ketones to α, β–unsaturated compounds was found to be highly selective to give 1, 2 addition products.
Regioselective addition reactions of silyl enolates to a, b-unsaturated aldehyde and its acetal catalyzed by MgI2 etherate give aldol adducts (1, 2-addition) preferentially over Michael adducts (1, 4-addition). This ...Regioselective addition reactions of silyl enolates to a, b-unsaturated aldehyde and its acetal catalyzed by MgI2 etherate give aldol adducts (1, 2-addition) preferentially over Michael adducts (1, 4-addition). This unique regioselectivity is distinctly different with other Lewis acidic promoters and may be attributed to the high oxyphilicity of IMg+.展开更多
Substituent, temperature and solvent effects on tautomeric equilibria in several β-ketoamides have been investigated by means of nuclear magnetic resonance spectroscopy (NMR). Keto-enol equilibrium predominates over ...Substituent, temperature and solvent effects on tautomeric equilibria in several β-ketoamides have been investigated by means of nuclear magnetic resonance spectroscopy (NMR). Keto-enol equilibrium predominates over the amide-imidol one. The relative stability of the individual tautomers and the corresponding equilibrium shifts are explained considering electronic and steric effects and tautomer stabilization via internal hydrogen bonds. In solution, these compounds exist mainly as ketoamide and Z-enolamide tautomers, both presenting intramolecular hydrogen bonds.展开更多
Chiral dialkyl carbinols and their derivatives are significant synthetic building blocks in organic chemistry and related fields.The development of convenient and efficient methods to access these compounds has long b...Chiral dialkyl carbinols and their derivatives are significant synthetic building blocks in organic chemistry and related fields.The development of convenient and efficient methods to access these compounds has long been an important endeavor.Herein,we report a NiH-catalyzed reductive hydroalkylation and hydroarylation of enol esters and ethers.α-Oxoalkyl organonickel species were generated in situ in a catalytic mode and then participated in cross-coupling with alkyl or aryl halides.This approach enabled C(sp^(3))–C(sp^(3))and C(sp^(3))–C(sp^(2))bond formation under mild reductive conditions with simple operations,thereby boosting a broad substrate scope and good functional compatibility.Esters of enantioenriched dialkyl carbinols were accessed in a catalytic asymmetric version.Mechanistic studies demonstrated that this reaction proceeded through a syn-addition of Ni–H intermediate to an enol ester with high regio-and enantioselectivity.展开更多
Treatment of enol ether or thiol enol ether of phenylethanals with sulfuric or polyphosphoric acid in toluene or xylene gave 2-phenylnaphthalene in good yield. More importantly, a one-pot reaction has been developed.
Summary of main observation and conclusion A general and efficient protocol to synthesize substituted olefins from carbonyl compounds via nickel catalyzed C-O activation of enolates was developed.Besides ketones,aldeh...Summary of main observation and conclusion A general and efficient protocol to synthesize substituted olefins from carbonyl compounds via nickel catalyzed C-O activation of enolates was developed.Besides ketones,aldehydes were also suitable substrates for the presented catalytic system to produce di-or tri-substituted olefins.It is worth noting that this approach exhibited good tolerance to highly reactive tertiary alcohols,which could not survive in other reported routes for converting carbonyl compounds to olefins.This method also showed good regio-and stereo-selectivity for olefin products.Preliminary mechanistic studies indicated that the reaction was accomplished through nickel catalyzed C-O activation of enolates,thus offering helpful contribution to current enol chemistry.展开更多
The reaction of silyl enol ethers (la-le) with perfluoroalkyl iodides (2f-2k) initiated with sodium dithionite was studied, α-Perfluoroalkyl ketones (3) were synthesized in excellent yield by this method, α,β-Unsat...The reaction of silyl enol ethers (la-le) with perfluoroalkyl iodides (2f-2k) initiated with sodium dithionite was studied, α-Perfluoroalkyl ketones (3) were synthesized in excellent yield by this method, α,β-Unsaturated fluorinated ketones (4) were obtained easily by dehydrofluorination of the α-perfluoroalkyl ketones. A radical mechanism was proposed.展开更多
An efficient synthesis of chiral benzannulated spiroketals via catalytic asymmetric[3+2]cycloaddition of exocyclic enol ethers with p-quinones was achieved.The transformation was enabled by a chiral N,N′-dioxides/Tm^...An efficient synthesis of chiral benzannulated spiroketals via catalytic asymmetric[3+2]cycloaddition of exocyclic enol ethers with p-quinones was achieved.The transformation was enabled by a chiral N,N′-dioxides/Tm^(Ⅲ)complex as the Lewis acid catalyst and afforded a series of enantiomerically enriched benzannulated spiroketal derivatives in good yields(up to 99%)and enantioselectivities(up to 98%ee).Topographic steric maps and distribution of the buried volumes of the catalysts via Cavallo’s SambVca 2 tool were used to elucidate the enantioinduction raised by the ligands and the metal ions.展开更多
Diphenyl diamine-based phosphonyl imines attached by the N-isopropyl group in the auxiliary have been synthesized in good yields under convenient reaction conditions.These new chiral N-phosphonyl imines can react with...Diphenyl diamine-based phosphonyl imines attached by the N-isopropyl group in the auxiliary have been synthesized in good yields under convenient reaction conditions.These new chiral N-phosphonyl imines can react with glycine enolate smoothly to give chiral α-β diamino esters in good yields(72%-90%) and up to excellent diastereoselectivity(】99:1 dr).By treatment with HBr,the chiral auxiliary can be readily removed.The absolute structure has been unambiguously determined by converting a product to a known sample.展开更多
When α-alkoxy-β-ketophosphonates,prepared by the Rh(Ⅱ) mediated insertion reaction of α-diazo-β-ketophosphonates into the OH bond of primary alcohols,were reduced either by NaBH4 in the presence of CaCl2 or by DI...When α-alkoxy-β-ketophosphonates,prepared by the Rh(Ⅱ) mediated insertion reaction of α-diazo-β-ketophosphonates into the OH bond of primary alcohols,were reduced either by NaBH4 in the presence of CaCl2 or by DIBAL,they respectively gave the corresponding anti or syn stereomeric hydroxyphosphonates with pronounced to complete stereoselectivity.Submitted to the action of potassium tert-butoxyde,syn isomers led to the corresponding pure(E) enol ethers in moderate to good yields.Under the same conditions anti isomers led to a mixture of(Z) and(E) enol ethers in rather poor yields.The sequence was applied to the preparation of some allyl-vinyl ethers with a(E) configuration for the vinylic double bond.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 21472046, 21372079)Science and Technology Commission of Shanghai Municipality (No. 16391902300)the Fundamental Research Funds for the Central Universities (No. 222201718004)
文摘Spirotetramat metabolizes to its active enol form in the plant. We described here a photocaged pesticide delivery system that can release insecticidal spirotetramat enol form upon light irradiation. Covalently linking spirotetramat-enol with photoresponsive coumarin generated the caged insecticide. The photophysical and photochemical properties, deprotection photolysis and insecticidal activities of the caged spirotetramat enol were studied. This light-triggered system can undergo cleavage to release free spirotetramat enol form at the presence of blue light （420 nm） or sunlight, Bioassays indicated that the triggered molecule has no obvious insecticidal activity against Aphis craccivora Koch at dark and could be activated by light to release the insecticidal ingredients, which provides precise control over insecticide delivery.
基金supported by the Research Fund for the Doctoral Program of Higher Education(No.20110002110052)
文摘Keto-enol tautomers of curcumin were confirmed by reversed-phase liquid chromatography（RPLC）/ hybrid quadrupole ion trap/time-of-flight mass spectrometry（QIT/TOFMS）.Tautomers gave different MS/MS spectra in negative mode.Different mass spectra were also obtained by hydrogen/deuterium exchange LC/MS/MS in positive mode.Our results suggest that enol form is the major form in the solution（water/acetonitrile）.
基金We thank NSFC(No.21002079)Project(No.20096203120002)supported by the Ministry of Education of the People's Republic of China.We also thank the third Knowledge and Technological Innovation Project(No.NWNUKJCXGC -03-75 and NWNU-KJCXGC-03-64) of Northwest Normal University for supporting our research
文摘A domino reaction of anilines with cyclic and acyclic enol ethers induced by catalytic amounts of TBPA^（·＋）（5 mol%） was investigated and a series of 2,4-disubstituted-1,2,3,4-tetrahydroquinolines were synthesized.Different from cyclic enol ethers, when acyclic enol ethers were used in the reaction,they serve as surrogates of acetaldehyde,producing a series of 2-methyl-4- anilino-1,2,3,4-tetrahydroquinolines.A single electron transfer mechanism was proposed to rationalize the products formation.
文摘The nucleophilic addition of Ti(IV) enolate derived from methyl aryl ketones to α, β–unsaturated compounds was found to be highly selective to give 1, 2 addition products.
基金We are grateful for the financial supports from the National Outstanding Youth Fund No.29925204)the Foundation for University Key Teacher by the Ministry of Education of Chinaa Visiting Fund of the National Laboratory of Applied Organic Chemistry.
文摘Regioselective addition reactions of silyl enolates to a, b-unsaturated aldehyde and its acetal catalyzed by MgI2 etherate give aldol adducts (1, 2-addition) preferentially over Michael adducts (1, 4-addition). This unique regioselectivity is distinctly different with other Lewis acidic promoters and may be attributed to the high oxyphilicity of IMg+.
文摘Substituent, temperature and solvent effects on tautomeric equilibria in several β-ketoamides have been investigated by means of nuclear magnetic resonance spectroscopy (NMR). Keto-enol equilibrium predominates over the amide-imidol one. The relative stability of the individual tautomers and the corresponding equilibrium shifts are explained considering electronic and steric effects and tautomer stabilization via internal hydrogen bonds. In solution, these compounds exist mainly as ketoamide and Z-enolamide tautomers, both presenting intramolecular hydrogen bonds.
基金the National Natural Science Foundation of China(grant nos.21732006,51821006,21927814,and 51961135104)the Strategic Priority Research Program of CAS(grant nos.XDB20000000 and XDB37040000)+1 种基金the USTC Research Funds of the Double First-Class Initiative(grant no.YD3530002002)the Users with Excellence Program of Hefei Science Center CAS(grant nos.2019HSCUE017 and 2019HSC-UE005).
文摘Chiral dialkyl carbinols and their derivatives are significant synthetic building blocks in organic chemistry and related fields.The development of convenient and efficient methods to access these compounds has long been an important endeavor.Herein,we report a NiH-catalyzed reductive hydroalkylation and hydroarylation of enol esters and ethers.α-Oxoalkyl organonickel species were generated in situ in a catalytic mode and then participated in cross-coupling with alkyl or aryl halides.This approach enabled C(sp^(3))–C(sp^(3))and C(sp^(3))–C(sp^(2))bond formation under mild reductive conditions with simple operations,thereby boosting a broad substrate scope and good functional compatibility.Esters of enantioenriched dialkyl carbinols were accessed in a catalytic asymmetric version.Mechanistic studies demonstrated that this reaction proceeded through a syn-addition of Ni–H intermediate to an enol ester with high regio-and enantioselectivity.
文摘Treatment of enol ether or thiol enol ether of phenylethanals with sulfuric or polyphosphoric acid in toluene or xylene gave 2-phenylnaphthalene in good yield. More importantly, a one-pot reaction has been developed.
文摘Summary of main observation and conclusion A general and efficient protocol to synthesize substituted olefins from carbonyl compounds via nickel catalyzed C-O activation of enolates was developed.Besides ketones,aldehydes were also suitable substrates for the presented catalytic system to produce di-or tri-substituted olefins.It is worth noting that this approach exhibited good tolerance to highly reactive tertiary alcohols,which could not survive in other reported routes for converting carbonyl compounds to olefins.This method also showed good regio-and stereo-selectivity for olefin products.Preliminary mechanistic studies indicated that the reaction was accomplished through nickel catalyzed C-O activation of enolates,thus offering helpful contribution to current enol chemistry.
文摘The reaction of silyl enol ethers (la-le) with perfluoroalkyl iodides (2f-2k) initiated with sodium dithionite was studied, α-Perfluoroalkyl ketones (3) were synthesized in excellent yield by this method, α,β-Unsaturated fluorinated ketones (4) were obtained easily by dehydrofluorination of the α-perfluoroalkyl ketones. A radical mechanism was proposed.
基金the National Natural Science Foundation of China(Nos.21890723 and 21921002)the Science and Technology Department of Sichuan Province(Nos.2021YJ0561)for financial support.
文摘An efficient synthesis of chiral benzannulated spiroketals via catalytic asymmetric[3+2]cycloaddition of exocyclic enol ethers with p-quinones was achieved.The transformation was enabled by a chiral N,N′-dioxides/Tm^(Ⅲ)complex as the Lewis acid catalyst and afforded a series of enantiomerically enriched benzannulated spiroketal derivatives in good yields(up to 99%)and enantioselectivities(up to 98%ee).Topographic steric maps and distribution of the buried volumes of the catalysts via Cavallo’s SambVca 2 tool were used to elucidate the enantioinduction raised by the ligands and the metal ions.
基金supported by the National Institutes of Health (Grant Nos.1 RO3 DA026960-01)Robert Welch Foundation (Grant No.D-1361)
文摘Diphenyl diamine-based phosphonyl imines attached by the N-isopropyl group in the auxiliary have been synthesized in good yields under convenient reaction conditions.These new chiral N-phosphonyl imines can react with glycine enolate smoothly to give chiral α-β diamino esters in good yields(72%-90%) and up to excellent diastereoselectivity(】99:1 dr).By treatment with HBr,the chiral auxiliary can be readily removed.The absolute structure has been unambiguously determined by converting a product to a known sample.
文摘When α-alkoxy-β-ketophosphonates,prepared by the Rh(Ⅱ) mediated insertion reaction of α-diazo-β-ketophosphonates into the OH bond of primary alcohols,were reduced either by NaBH4 in the presence of CaCl2 or by DIBAL,they respectively gave the corresponding anti or syn stereomeric hydroxyphosphonates with pronounced to complete stereoselectivity.Submitted to the action of potassium tert-butoxyde,syn isomers led to the corresponding pure(E) enol ethers in moderate to good yields.Under the same conditions anti isomers led to a mixture of(Z) and(E) enol ethers in rather poor yields.The sequence was applied to the preparation of some allyl-vinyl ethers with a(E) configuration for the vinylic double bond.
