Abstract
Upon irradiation at lambda = 350 nm, cyclohept-2-enone undergoes an isomerization to the strained (E)-isomer. The process was studied by XMS-CASPT2 calculations and found to proceed by two competitive reaction channels on either the singlet or the triplet hypersurface. (E)-Cyclohept-2-enone is a reactive dienophile in thermal [4 + 2] cycloaddition reactions with various dienes. Ten different dienes were probed, most of which-except for 1,3-cyclohexadiene-underwent a clean Diels-Alder reaction and gave the respective trans-fused six-membered rings in good yields (68-98%). The reactions with furan were studied in detail, both experimentally and by DLPNO-CCSD(T) calculations. Two diastereoisomers were formed in a ratio of 63/35 with the exo-product prevailing, and the configuration of both diastereoisomers was corroborated by single crystal X-ray crystallography. The outcome of the photoinduced Diels-Alder reaction matched both qualitatively and quantitatively the calculated reaction pathway. Apart from cyclohept-2-enone, five additional cyclic hept-2-enones and cyclooct-2-enone were employed in their (E)-form as dienophiles in the Diels-Alder reaction with 1,3-cyclopentadiene (80-98% yield). The method was eventually applied to a concise total synthesis of racemic trans-alpha-himachalene (four steps, 14% overall yield).
| Dokumententyp: | Zeitschriftenartikel |
|---|---|
| Fakultät: | Chemie und Pharmazie > Department Chemie |
| Themengebiete: | 500 Naturwissenschaften und Mathematik > 540 Chemie |
| ISSN: | 0022-3263 |
| Sprache: | Englisch |
| Dokumenten ID: | 111468 |
| Datum der Veröffentlichung auf Open Access LMU: | 02. Apr. 2024, 07:26 |
| Letzte Änderungen: | 02. Apr. 2024, 07:26 |
| DFG: | Gefördert durch die Deutsche Forschungsgemeinschaft (DFG) - 444632635 |
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