Conjugated esters were instantaneously hydrodimerized at room temperature by use of the reduction system, Sml2-THF-HMPA, in the presence of proton sources. A perfect stereoselection was realized in the reaction of N,N-dibenzyl crotonamide.
Cyclisation of α,β,γ,ψ-unsaturated dioic acid esters via tandem conjugate additions by using lithium N-benzyltrimethylsilylamide (LSA) as a nitrogen nucleophile and its application to a total synthesis of (±)-dihydronepetalactone and (±)-isodihydronepetalactone
作者:Tadao Uyehara、Naomi Shida、Yoshinori Yamamoto
DOI:10.1039/c39890000113
日期:——
A stereoselective totalsynthesis of (±)-dihydronepetalactone and (±)-isodihydronepetalactone has been accomplished by utilising a novel cyclisation procedure; a reaction of octadiene-2,6-dioic acidesters with lithiumN-benzyltrimethylsilylamide (LSA) induces 5-exo-Trig ring-closure viatandemconjugateadditions.
One-Pot O<sub>2</sub>-Oxidation and the Horner–Wadsworth–Emmons Reaction of Primary Alcohols for the Synthesis of (<i>Z</i>)-α,β-Unsaturated Esters
作者:Kaori Ando、Chika Takaba、Masahiro Kodama
DOI:10.1021/acs.joc.2c00763
日期:2022.8.5
primary alcohols giving Z-α,β-unsaturated esters 3. TEMPO-(CuCl or CuBr2)-(2,2′-bipyridine) (1:1:1) catalyzed O2 oxidation of primary alcohols in the presence of Z-selective Horner–Wadsworth–Emmons reagent 1b and K3PO4 or NaH gave 3 with Z/E = 84:16 to 96:4 in high yields. A stepwise reaction was also developed. After TEMPO-CuBr2-(2,2′-bipyridine)-K3PO4 (1:1:1:1) catalyzed O2 oxidation of alcohols in MeCN
我们开发了伯醇的一锅氧化/烯化程序,得到Z -α,β-不饱和酯3。TEMPO-(CuCl 或 CuBr 2 )-(2,2'-联吡啶) (1:1:1) 在Z选择性 Horner-Wadsworth-Emmons 试剂1b和 K 3 PO 4存在下催化伯醇的 O 2氧化或 NaH以Z / E = 84:16 至 96:4 的高产率得到3 。还开发了逐步反应。TEMPO-CuBr 2 -(2,2'-联吡啶)-K 3 PO 4 (1:1:1:1)催化O 2后在 MeCN 中氧化醇,所得混合物在 -78 °C 至 0 °C 下用1b和t -BuOK 的 THF 溶液处理,得到具有更高选择性的3 ( Z / E = 91:9 至 99:1)。
New type of cyclization of .alpha.,.beta.,.chi.,.psi.-unsaturated dioic acid esters through tandem conjugate additions by using lithium N-benzyl-N-(trimethylsilyl)amide as a nitrogen nucleophile
作者:Tadao Uyehara、Naomi Shida、Yoshinori Yamamoto
DOI:10.1021/jo00037a034
日期:1992.5
Treatment of dimethyl (2E,6E)-2,6-octadienedioate with lithium N-benzyl-N-(trimethylsilyl)amide (LSA) gave 5-exo-trig ring closure products, methyl 3-(N-benzylamino)-2-(methoxycarbonyl)cyclopentane-1-acetates, through tandem conjugate additions. The related 6-exo-trig cyclization proceeded stereoselectively to give ethyl c-3-(N-benzylamino)-t-2-(ethoxycarbonyl)cyclohexane-1-acetate. In contrast with the 5- and 6-exo-trig cyclization, no 7-exo-trig cyclization occurred. The 5-exo-trig cyclization products were converted into 2-(methoxycarbonyl)-2-cyclopentene-1-carboxylic acid methyl ester in an excellent yield. 5-exo-trig cyclization of the unsymmetrical dienedioate consisting of crotonate and (E)-2-methyl-2-butenoate units proceeded regioselectively through conjugate addition of LSA to the crotonate part. Similar regioselectively was observed in the case of 5-exo-trig cyclization of the dienedioate possessing crotonate and (E)-3-methyl-2-pentenoate units. Total syntheses of the physiologically active cyclopentane monoterpenes (+/-)-dihydronepetalactone and (+/-)-isohydronepetalactone has been accomplished by this cyclization strategy. In addition, it has been demonstrated that LSA is a more efficient nitrogen nucleophile than LDA to cyclize omega-halo-alpha,beta-unsaturated esters.
Ruthenium-catalyzed oxidative cyclization of 1,7-dienes. A novel diasteroselective synthesis of 2,7-disubstituted trans-oxepane diols
The ruthenium-catalyzed oxidation of some representative 1,7-dienes has been investigated. Tetrasubstituted 1,7-dienes are transformed into the corresponding trans-2,7-bis-hydroxyalkyl-oxepanes through an oxidative cyclization process. The process proceeds with an excellent stereo selectivity level. (C) 2007 Elsevier Ltd. All rights reserved.