A novel nucleophilic substitution of pyridazines is found, in which phenoxy group is dislodged rather than the halogen atom, on treating 3-halo-6-phenoxypyridazines with alkoxy anion. The reactivity of substituents on...A novel nucleophilic substitution of pyridazines is found, in which phenoxy group is dislodged rather than the halogen atom, on treating 3-halo-6-phenoxypyridazines with alkoxy anion. The reactivity of substituents on benzene ring and the halogen atom of pyridazines are studied. Reasonable explanation based on the quantum chemical calculations are given.展开更多
Topomerization of [9] annulen anion （1） and its 2-fluoro-, 2-chloro- and 2- bromo-defivatives （2, 3 and 4, respectively） are studied at the HF/6-31G＊ and B3LYP/6-31 1＋＋G＊＊ levels of theory. The relative ease ...Topomerization of [9] annulen anion （1） and its 2-fluoro-, 2-chloro- and 2- bromo-defivatives （2, 3 and 4, respectively） are studied at the HF/6-31G＊ and B3LYP/6-31 1＋＋G＊＊ levels of theory. The relative ease of topomerization is dependent on the charge distribution and planarity of the ground state and the transition state of 9-membered rings as well as the size and electronegativity of halogen substituent. Consequently, the endo-2-halo-[9] annulen anion topomers become unstable and easily convert to related exo-topomers. Hence, according to the DFT calcu- lations, the order of topomerization energy barrier for endo = exo topomerization is lendo 〉 2endo 〉 3endo.展开更多
The sequential oxidation-Horner-Wadsworth-Emmons reaction of alcohols to prepare α-Halo-α,β-unsaturated esters （halo =F, Cl） with middle to excellent （Z）-selectivity was developed.
Due to the chemoselective dehalogenation by SmI2, the addition of α-halomethylsulfones to carbonyl compounds afforded β-hy-droxysulfones. Those reactions with α-bromomethylsulfones gave the products in moderate to ...Due to the chemoselective dehalogenation by SmI2, the addition of α-halomethylsulfones to carbonyl compounds afforded β-hy-droxysulfones. Those reactions with α-bromomethylsulfones gave the products in moderate to good yields. The SmI2-mediat-ed addition of gem-dihalomethylsulfones to ketones also afforded α-halo-β-hydroxysulfones in moderate yields.展开更多
The hydrohalogenation reaction of 1-alkyl substituted 1,2-allenyl carboxylic acid esters (1) with MX (M= Na, or Li, X= Cl, Br, I) afforded a mixture of β,γ-unsaturated 3-halo–3-alkenoates (2) and Q,P unsaturated 3-...The hydrohalogenation reaction of 1-alkyl substituted 1,2-allenyl carboxylic acid esters (1) with MX (M= Na, or Li, X= Cl, Br, I) afforded a mixture of β,γ-unsaturated 3-halo–3-alkenoates (2) and Q,P unsaturated 3-halo-2-alkenoates (3) in HOAc, while using a mixture of HOAC-CF3CO2H (1:1) or CF3C2H as the reaction medium the corresponding reaction cleanly produced β,γ -unsaturated 3-hale3-alkenoates (2) as the sole products in high yields. The subsequent coupling reactions were studied.展开更多
文摘A novel nucleophilic substitution of pyridazines is found, in which phenoxy group is dislodged rather than the halogen atom, on treating 3-halo-6-phenoxypyridazines with alkoxy anion. The reactivity of substituents on benzene ring and the halogen atom of pyridazines are studied. Reasonable explanation based on the quantum chemical calculations are given.
文摘Topomerization of [9] annulen anion （1） and its 2-fluoro-, 2-chloro- and 2- bromo-defivatives （2, 3 and 4, respectively） are studied at the HF/6-31G＊ and B3LYP/6-31 1＋＋G＊＊ levels of theory. The relative ease of topomerization is dependent on the charge distribution and planarity of the ground state and the transition state of 9-membered rings as well as the size and electronegativity of halogen substituent. Consequently, the endo-2-halo-[9] annulen anion topomers become unstable and easily convert to related exo-topomers. Hence, according to the DFT calcu- lations, the order of topomerization energy barrier for endo = exo topomerization is lendo 〉 2endo 〉 3endo.
文摘The sequential oxidation-Horner-Wadsworth-Emmons reaction of alcohols to prepare α-Halo-α,β-unsaturated esters （halo =F, Cl） with middle to excellent （Z）-selectivity was developed.
基金Project supported by the National Natural Science Foundation of China(No.20272050).
文摘Due to the chemoselective dehalogenation by SmI2, the addition of α-halomethylsulfones to carbonyl compounds afforded β-hy-droxysulfones. Those reactions with α-bromomethylsulfones gave the products in moderate to good yields. The SmI2-mediat-ed addition of gem-dihalomethylsulfones to ketones also afforded α-halo-β-hydroxysulfones in moderate yields.
基金National Natural Science Foundation of China (No. 29525202)Shanghai Municipal Cormnittee of Science and Technology (No. 98QA14001).
文摘The hydrohalogenation reaction of 1-alkyl substituted 1,2-allenyl carboxylic acid esters (1) with MX (M= Na, or Li, X= Cl, Br, I) afforded a mixture of β,γ-unsaturated 3-halo–3-alkenoates (2) and Q,P unsaturated 3-halo-2-alkenoates (3) in HOAc, while using a mixture of HOAC-CF3CO2H (1:1) or CF3C2H as the reaction medium the corresponding reaction cleanly produced β,γ -unsaturated 3-hale3-alkenoates (2) as the sole products in high yields. The subsequent coupling reactions were studied.
