Journal ArticleDOI
Inter- and Intramolecular Hetero Diels-Alder Reactions, Part XXVI. Diastereoselectivity and Kinetics of Intermolecular Hetero Diels-Alder Reactions under High Pressure. A Significant Pressure-Induced Increase in Stereoselectivity
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TLDR
In this article, the Hetero Diels-Alder reaction of enamino ketones 5a-d and ethyl vinyl ether (2) to give the dihydropyrans 6a−d and 7a−c was studied in dichloromethane and in heptane/isodurene under high pressure up to 7 kbar at temperatures between 0.5 and 130°C.Abstract:
The Hetero Diels-Alder reaction of the enamino ketones 5a–d and ethyl vinyl ether (2) to give the dihydropyrans 6a–d and 7a–d is studied in dichloromethane and in heptane/isodurene under high pressure up to 7 kbar at temperatures between 0.5 and 130°C. The kinetics is measured by on-line FT-IR spectroscopy. The cycloaddition shows a remarkable pressure-dependent increase of diastereoselectivity in favour of the cis adducts 6a–c with the largest effect found for the reaction of 5a and the smallest for 5c. The pressure-averaged overall activation volumes ΔV≠ in dichloromethane are determined to be between –(23.4± 1.0) and –(24.2±1.0) cm3/mol. The ΔΔV≠ values for the cycloaddition of 5a, 5b, and 5c are –(5.9±0.5), –(3.9±0.1), and –(2.4±0.2) cm3/mol, respectively, and the ΔΔH≠ values are –(8.1±1.7), –(8.7±2.7), and –(10.0±0.9 kJ/mol, respectively. Because of the favourable ΔΔV≠ and ΔΔH≠, the selectivity of the reaction of 5a to give 6a/7a can be increased from 1.67: 1.00 at 90°C and 1 bar to 13.6:1.0 at 0.5°C and 6 kbar. This example shows that a significant and synthetic useful increase of diastereoselectivity in chemical reactions is possible by applying high pressure.read more
Citations
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Book ChapterDOI
Hetero diels-alder reactions in organic chemistry
Lutz F. Tietze,Georg Kettschau +1 more
TL;DR: In this article, an overview is given for the period since 1989 describing the reaction of heterobutadienes and other dienophiles such as carbonyls, thiocarbonyls and iminium salts.
Journal ArticleDOI
Domino-reactions: The tandem-knoevenagel-hetero-diels-alder reaction and its application in natural product synthesis
Patent
Process for producing 4-trifluoromethylnicotinic acid
Toru Koyanagi,o Ishihara Sangyo Kaisha Ltd. Tanimura,Fumio Kanamori,Shigehisa Kanbayashi,Toyoshi Tanimura,Noriyuki Horiuchi +5 more
TL;DR: A process for producing 4-trifluoromethylnicotinic acid of the formula (VIII) or its salt is described in this article, which comprises (i) a first step of reacting a halide of the formulation (I): CF3COHal (I) wherein Hal is a halogen atom, with a compound (II): CH2=CHOR1 (II) wherein R1 is an alkyl group, in the presence of a base to obtain a 4-alkoxy-1,1, 1, 1-tr
Journal ArticleDOI
The Effect of Pressure on Organic Reactions
TL;DR: In this paper, the utility of high pressure for the understanding of chemical reactions and its application in organic synthesis is shown for cycloadditions, cheletropic reactions and pericyclic rearrangements.
References
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Journal ArticleDOI
Mechanistic Aspects of Diels‐Alder Reactions: A Critical Survey
Jürgen Sauer,Reiner Sustmann +1 more
TL;DR: In this paper, a line of distinction between the mechanistic alternatives for the Diels-Alder reaction was drawn, considering all experimental and theoretical criteria, for one-step and two-step reactions.
Book
Hetero Diels-Alder methodology in organic synthesis
Dale L. Boger,Steven M. Weinreb +1 more
TL;DR: In this article, N-Sulfinyl Compounds and Sulfur Diimides are classified into three classes: Nitroso and Thionitroso Dienophiles.
Journal ArticleDOI
Activation and Reaction Volumes in Solution. 3.
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