Diels−Alder Reactions of 5-Alkyl-1,3-cyclopentadienes
作者:Johnathon E. Letourneau、Mark A. Wellman、D. Jean Burnell
DOI:10.1021/jo9707949
日期:1997.10.1
preference for syn addition with less encumbered dienophiles. This may indicate a conformational difference in its syn transition state relative to the transition states for addition syn to methyl, ethyl, or n-butyl substituents (dienes 1, 4, and 5). Dienophiles are more reluctant to add syn to the larger C-5 group with 1,2,3,4,5-pentamethyl-1,3-cyclopentadiene (2) and derivatives (3, and 7) and conformational
4-Alkoxymethyl-5-chloro-5-cyano-2-norbornene (III) was produced by the Diels-Alder reaction using 5-alkoxymethyl-cyclopentadiene and α-chloroacrylonitrile in the presence of aqueous cupric boronfluoride. III was hydrolyzed to 4-alkoxymethyl-2-norbornen-5-one (V). When V was oxidized with m-chloroperbenzoic acid, the products were varied by differences of the reaction conditions. (3β-Methoxymethyl-3α-hydroxy-4-cyclopenten-1α-yl)-acetic acid lactone (IXa) was produced by the oxidation of 4-meth-oxymethyl-2-norbornen-5-one (Va) with m-chloroperbenzoic acid in the presence of aqueous sodium bicarbonate. IXa which was very unstable was easily rearranged to 5-meth-oxymethyl-3, 3aβ, 4, 6aβ-tetrahydro-2H-cyclopenta [b] furan-2-one (Xa).
Enantioselective Diels-Alder Cycloadditions with β-Substituted Pyrazolidinone Propiolimides
作者:Mukund Sibi、Wilfredo Cruz Jr.、Levi Stanley
DOI:10.1055/s-0029-1219538
日期:2010.4
Chiral Lewis acid catalyzed Diels-Alder cycloadditions between β-substituted pyrazolidinone propiolimides and cyclic dienes have been studied. A catalyst prepared from Sc(OTf)3 and t-Bu-pybox ligand promotes the formation of enantioenriched diene cycloadducts in moderate to high yield and good enantioselectivity from the reactions of acetylenic dienophiles and cyclic dienes.