Domino [3+3] Annulation/Ring-Cleavage Reactions of 1,3-Bis(trimethylsilyloxy)-1,3-butadienes with 5-Aryl- and 5-Vinyl-3-acyl- 4,5-dihydrofurans: Efficient Synthesis of 5-(4-Chlorobut-2-en-1-yl)- and 5-(2-Aryl-2-chloroethyl)salicylates
The domino “[3+3] cyclization–ring-opening” reactions of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-acetyl-5-vinyl-4,5-dihydrofurans afforded 5-(4-halobut-2-en-1-yl)salicylates. The reactions of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-acetyl-5-aryl-4,5-dihydrofurans gave 5-(2-aryl-2-chloroethyl)salicylates.
Non-decarbonylative photochemical versus thermal activation of Bu<sub>4</sub>N[Fe(CO)<sub>3</sub>(NO)] – the Fe-catalyzed Cloke–Wilson rearrangement of vinyl and arylcyclopropanes
作者:Che-Hung Lin、Dominik Pursley、Johannes E. M. N. Klein、Johannes Teske、Jennifer A. Allen、Fabian Rami、Andreas Köhn、Bernd Plietker
DOI:10.1039/c5sc02342d
日期:——
The base metal complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) catalyzes the rearrangement of vinyl and arylcyclopropanes both under thermal or photochemical conditions to give the corresponding vinyl or aryldihydrofuranes in good to excellent...
Electronic and steric effects in the addition of electrophilic 1,3-dicarbonylalkyl radicals to styrenes
作者:Enrico Baciocchi、Renzo Ruzziconi
DOI:10.1021/jo00015a037
日期:1991.7
The addition reactions of 1,3-dicarbonylalkyl radicals to ring-substituted styrenes have been kinetically investigated in MeOH and/or MeCN. It has been observed that the rate effect of ring substituents is nearly identical in the reactions of MeCOCHCOMe (1), MeOCOCHCOMe (2) and MeOCOCHCOOMe (4), the rho-value, in MeOH being -0.96, -1.01 and -1.06, respectively. Since the three radicals are relatively strong oxidants and have similar reduction potentials, an important contribution of the charge transfer structure RCOCHCORCH2CHAr.+ to the addition transition state is suggested. It has also be found that in the reactions of 1 and 4 with alpha-alkyl-substituted styrenes the rate of addition is strongly influenced by the nature of the alkyl group, decreasing in the order: Me > Et > (i)Pr > (t)Bu. The observed effects are much larger than those reported for the corresponding reactions of the nucleophilic cyclohexyl radical. It is suggested that the alpha-alkyl substituents exert an effect of steric inhibition of resonance thereby ring delocalization of the charge and/or unpaired electron in the transition state is significantly reduced. Delocalization may be more important in the reactions of 1 and 4 than in those of the cyclohexyl radical since it is possible that the former utilizes a transition state occurring later along the reaction coordinate and/or characterized by a larger extent of charge transfer.
Synthesis of 5-(2-aryl-2-haloethyl)salicylates by the first domino ‘[3+3] cyclization/ring-cleavage’ reactions of 1,3-bis(silyloxy)-1,3-butadienes with 3-acetyl-5-aryl-4,5-dihydrofurans
作者:Matthias Lau、Peter Langer
DOI:10.1016/j.tetlet.2008.07.049
日期:2008.9
5-(2-Aryl-2-haloethyl)salicylates are efficiently prepared by the first domino '[3+3] cyclization/ring-cleavage' reactions of 1,3-bis(silyloxy)-1,3-butadienes with 3-acetyl-5-aryl,5-dihydrofurans. (C) 2008 Elsevier Ltd. All rights reserved.
Organocatalytic Cloke–Wilson Rearrangement: DABCO-Catalyzed Ring Expansion of Cyclopropyl Ketones to 2,3-Dihydrofurans
An organocatalytic Cloke–Wilson rearrangement of cyclopropyl ketones to 2,3-dihydrofurans is exploited utilizing the homoconjugate addition process. With 1,4-diazabicyclo[2.2.2]octane as the catalyst, the rearrangement in DMSO at 120 °C proceeded in generally high yields, exclusive regioselectivity, and a broad substrate scope. An examination of the mechanism including stereochemical analysis and intermediate