Enantioselective synthesis of allenecarboxylates from phenyl acetates through CC bond forming reactions
摘要:
A variety of optically active 4,4-disubstituted allenecarboxylic acid methyl esters were prepared from simple alpha,alpha -disubstituted phenyl acetate through base treatment of the esters to generate ketenes, followed by successive Horner-Wadsworth-Emmons reaction. The transformation was further developed as a one-pot procedure with satisfactory yields and high enantioselectivity. (C) 2001 EIsevier Science Ltd. All rights reserved.
<sup>1</sup>H-NMR.-spektroskopische Bestimmung der Enantiomerenreinheit von Allencarbonsäureestern mit optisch aktiven Europium-Verschiebungsreagenzien
作者:Robert W. Lang、Hans-Jürgen Hansen
DOI:10.1002/hlca.19790620413
日期:1979.6.8
1H-NMR. Spectroscopic Determination of Enantiomeric Purities of Allenic Esters UsingOpticallyActiveEuropiumShiftReagents
1 H-NMR。使用光学活性Euro移位试剂的光谱测定烯丙基酯的对映体纯度
Synthesis of tetrasubstituted thiophenes <i>via</i> a [3+2] cascade cyclization reaction of pyridinium 1,4-zwitterionic thiolates and activated allenes
A [3+2] cascade cyclization reaction of pyridinium1,4-zwitterionicthiolates and activated allenes has been developed, which allows facile access to a library of tetrasubstituted thiophenes with great variety under thermal conditions.
Tandem thia-Michael/Dieckmann condensation of allenyl esters with methyl mercaptoacetate in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene afforded 2,3,5-trisubstituted thiophenes regioselectively. On the other hand, 2,3,4-trisubstituted thiophenes were obtained as the sole product by tandem thia-Michael/Dieckmann condensation employing magnesium bromide and triethylamine.
A tandem thia-Michael/aldolreaction of allenyl esters and mercaptoacetaldehyde in the presence of triethylamine provided 2,3,4-trisubstituted tetrahydrothiophenes. Novel 2,3-disubstituted thiophenes were obtained in high yield by the subsequent dehydration of the 2,3,4-trisubstituted tetrahydrothiophenes using p-toluenesulfonic acid monohydrate as an effective catalyst.
Enantioselective preparation of allenecarboxylates by asymmetric horner-wadsworth-emmons reaction
作者:Kiyoshi Tanaka、Kenji Otsubo、Kaoru Fuji
DOI:10.1016/0040-4039(96)00672-7
日期:1996.5
Optically active 4,4-disubstituted conjugated allenecarboxylates were enantioselectively prepared via CC bond formation through an asymmetric Horner-Wadsworth-Emmons reaction with an optically active phosphonoacetate reagent.