Direct synthesis of substituted tetrahydrofurans via regioselective dehydrative polyol cyclization cascades
摘要:
A one-pot procedure for the conversion of 1,2,4,5-tetraols into substituted tetrahydrofuran moieties has been developed. This involves the regioselective sulfonylation of the terminal hydroxyl of the polyol array followed by sequential oxirane and oxolane formation under basic conditions. A survey of reaction conditions has defined the use of N-(2,4,6-triisopropylbenzenesulfonyl)imidazole as sulfonylation reagent, potassium tert-butoxide as base, and tert-butanol as solvent to be optimal. Under these conditions, 8-O-benzyl-octan-1,2,4,5,8-pentaol was converted stereospecifically into tetrahydrofurans in 62% yield. Polyol substrates were derived from Sharpless asymmetric dihydroxylation of 1,4-dienes. Hence, substituted tetrahydrofurans could be obtained stereospecifically from diene substrates in two operations. (C) 2002 Elsevier Science Ltd. All rights reserved.
Chemoselective Cross-Metathesis Reaction. Application to the Synthesis of the C1−C14 Fragment of Amphidinol 3
作者:Samir BouzBouz、Janine Cossy
DOI:10.1021/ol0157095
日期:2001.5.1
[reaction: see text] An efficient synthesis of the C1-C14 fragment of amphidinol3 is described. The synthesis is based on chemoselective cross-metathesis reactions and enantioselective allyltitanations.
Preparation of (<i>E</i>)-1,3,5-Hexatriene and (3<i>E</i>, 5<i>E</i>)-1,3,5,7-Octatetraene by the Palladium Catalyzed Elimination of Acetic Acid from Allylic Acetates
作者:Keiji Yamamoto、Shigeaki Suzuki、Jiro Tsuji
DOI:10.1246/bcsj.54.2541
日期:1981.8
Palladium complex-catalyzed elimination of aceticacidfrom (2E,4E)-2,4-hexadienyl acetate and (2E, 4E, 6E)-2,4,6-octatrienyl acetate afforded, respectively, the title conjugated polyenes stereoselectively.
Substituted aromaticketoximes reacted efficiently with allylicacetates in the presence of [RuCl2(p‐cymene)]2} and AgSbF6 in 1,2‐dichloroethane at ambient temperature, providing ortho‐allyl aromaticketoximes in a highly regioselective manner without an oxidant. In the reaction, the acetate group of allyl acetate acts as a base to activate the CH bond of aromatics. Later, ortho‐allyl aromatic ketoximes
Regioselectivity and Stereoselectivity in Nitrile Oxide Cycloaddition to 1, 5-Hexadien-3-ol. The Study on the Hydrogen Bonding Effect and Magnesium Chelation Effect in Nitrile Oxide Cycloaddition
作者:Jae Nyoung Kim、Hyoung Rae Kim、Eung K. Ryu
DOI:10.1080/00397919308011265
日期:1993.6
1,3-Dipolar cycloaddition of 2,6-dichlorobenzonitrile oxide and 1.5-hexadien-3-ol showed regioselectivity to some extent by their hydrogen bonding effect. The chelation of magnesium metal instead of hydrogen bonding in the same reaction showed an excellent regioselectivity along with a good diastereoselectivity.