Experimental conditions for the intramolecular cycloaddition of four related pentadienyl acrylates 3, 4, 5 and 6 are reported. In contrast with several previous reports, pentadienyl acrylates do undergo synthetically useful intramolecular Diels-Alder reactions: 3, 4, 5 and 6 cyclise at reasonable rates at temperatures of 132-180 degrees C at atmospheric pressure in moderate to good yields. The stereochemical outcome of each of these reactions was accurately measured and the results are in good agreement with transition structure populations predicted using B3LYP/6-31+G(d) theory. The parent system 3 cyclises with moderate endo selectivity; the presence of either a C5-methyl substituent or a C3-bromine atom results in a slight shift towards the trans-fused exo stereoisomer but--overall--a less selective reaction. The presence of both C3-Br and C5-CH3 substituents results in a marked improvement in stereoselectivity with the exo,lk-product predominating. Interpretation of B3LYP/6-31+G(d) transition structures allows insights into the improvement in stereoselectivity obtained by incorporating a removable "steric directing group" into a 5-methyl-1,3,8-nonatriene precursor.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1002/1521-3765(20020201)8:3<739::AID-CHEM739>3.0.CO;2-1 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Rearrangements and intramolecular Diels-Alder reactions of normal and vinylogous aza-Morita-Baylis-Hillman products leading to isoindoline derivatives.
J Org Chem
June 2010
Department of Chemistry, University of Calgary, Calgary, AB, Canada T2N 1N4.
Aza-Morita-Baylis-Hillman (aza-MBH) products derived from arylimines and methyl acrylate or acrylonitrile were N-alkylated with (E)-5-bromopenta-1,3-diene, and the resulting trienes were subjected to intramolecular Diels-Alder (IMDA) cyloadditions to afford the corresponding trans- and cis-fused tetrahydroisoindolines as the major and minor products, respectively. Catalysis with boron trichloride improved the IMDA diastereoselectivities of the nitrile derivatives, while yields were improved in both the nitrile and ester series. Treatment of the nitrile-substituted trienes with DABCO in DMF resulted in unexpected transposition of the N-(pentadienyl)sulfonamide group to the beta-position of the acrylonitrile moiety.
View Article and Find Full Text PDFOn the origin of cis/trans stereoselectivity in intramolecular Diels-Alder reactions of substituted pentadienyl acrylates: a comprehensive density functional study.
J Org Chem
December 2005
School of Chemistry, The University of New South Wales, Sydney, NSW 2052, Australia.
[structures: see text] A gas-phase B3LYP/6-31+G(d) study of substituent effects on the stereochemistry of both intramolecular Diels-Alder (IMDA) reactions of 9-E- and 9-Z-substituted pentadienyl acrylates and intermolecular Diels-Alder (DA) reactions between butadiene and monosubstituted alkenes and 3-substituted acrylates is reported and involves the calculation of 230 transition structures. It was found that, although exo ("anti-Alder") addition of monosubstituted ethenes to butadiene is the norm, Alder endo selectivity is more widely predicted for 3-substituted methyl acrylate dienophiles, and this was explained in terms of secondary orbital interactions (SOIs). Whereas cis/trans selectivity for IMDA reactions involving 9-E-substituted pentadienyl acrylates generally follows the normal pattern found for the corresponding intermolecular DA reactions, the 9-Z-substituted stereoisomers generally displayed trans selectivity that was much stronger than can be attributed to effects of the isolated substituent.
View Article and Find Full Text PDFOptimising stereoselectivity in intramolecular Diels-Alder reactions of pentadienyl acrylates: synthetic and computational investigations into the "steric directing group" approach.
Chemistry
February 2002
School of Chemistry, University of Sydney, NSW, Australia.
Experimental conditions for the intramolecular cycloaddition of four related pentadienyl acrylates 3, 4, 5 and 6 are reported. In contrast with several previous reports, pentadienyl acrylates do undergo synthetically useful intramolecular Diels-Alder reactions: 3, 4, 5 and 6 cyclise at reasonable rates at temperatures of 132-180 degrees C at atmospheric pressure in moderate to good yields. The stereochemical outcome of each of these reactions was accurately measured and the results are in good agreement with transition structure populations predicted using B3LYP/6-31+G(d) theory.
View Article and Find Full Text PDFConformational study of the intramolecular diels-alder reaction of a pentadienyl acrylate. Theoretical evaluation of kinetic and thermodynamic control.
Org Lett
October 2000
Departments of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, and Emory University, Atlanta, Georgia 30322, USA.
Acrylate 4, prepared from diacetylrhamnal, underwent intramolecular Diels-Alder cycloaddition to give the thermodynamically disfavored trans-fused gamma-lactone 15 as the major product, along with two stereoisomeric cycloadducts. A computational analysis of each of the four transition states arising from 4 and the corresponding cycloadducts permits an understanding of the contrasting requirements for kinetic versus thermodynamic control of the reaction.
View Article and Find Full Text PDFNovel beta-methoxyacrylates of the 9-methoxystrobilurin and oudesmansin classes produced by the basidiomycete Favolaschia pustulosa.
J Nat Prod
July 1996
Senova, Ltd., Berkshire, U.K.
Submerged liquid cultures of the basidiomycete Favolaschia pustulosa (Xenova culture collection no. X27732) afforded the novel 9-methoxystrobilurin derivatives, 9-methoxystrobilurin L (1) and 9-methoxystrobilurin E (2), and the related oudemansin derivative, oudemansin L (3). Their structures were established by 2D NMR experiments.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!