Theoretical Study of the Concerted and Stepwise Mechanisms of Triazolinedione Diels−Alder Reactions
The Diels−Alder (DA) reactions of triazolinedione (TAD) with s-cis- and s-trans-butadiene have been investigated theoretically with density functional theory. All geometries were fully optimized at the Becke3LYP/6-31G* level. For butadiene, the asynchronous concerted pathway dominates; only stereosp...
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Published in | Journal of the American Chemical Society Vol. 120; no. 47; pp. 12303 - 12309 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
American Chemical Society
02.12.1998
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Online Access | Get full text |
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Summary: | The Diels−Alder (DA) reactions of triazolinedione (TAD) with s-cis- and s-trans-butadiene have been investigated theoretically with density functional theory. All geometries were fully optimized at the Becke3LYP/6-31G* level. For butadiene, the asynchronous concerted pathway dominates; only stereospecific DA products should be formed. The endo transition structure is 9.7 kcal/mol lower in energy than the exo TS; this exo-lone-pair preference comes from the electrostatic repulsion of the lone pairs on nitrogens with the π-system of butadiene. The stepwise mechanism leads to an aziridinium imide (AI) intermediate. The stepwise formation of AI intermediates is only 2.9−6.0 kcal/mol higher in energy than the asynchronous concerted mechanism. The AI intermediates can open to form a diradical or zwitterion which can react to yield nonstereospecific Diels−Alder, ene, or solvent-trapping products. |
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Bibliography: | istex:BEDB6C707DFACF3C84F01FFDD68B2034CA94301E ark:/67375/TPS-2Z0TN95H-N |
ISSN: | 0002-7863 1520-5126 |
DOI: | 10.1021/ja982050y |