Complete control of regioselectivity in the intramolecular [2 + 2] photocycloaddition of 2-alkenyl-3(2H)-furanones by the length of the side chain |
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Authors: | Bach Thorsten Kemmler Michael Herdtweck Eberhardt |
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Institution: | Lehrstuhl für Organische Chemie I and Lehrstuhl für Anorganische Chemie, Technische Universit?t München, D-85747 Garching, Germany. thorsten.bach@ch.tum.de |
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Abstract: | The 2-(omega-alkenyl)-substituted 2-methyl-3(2H)-furanones 2a and 2b were prepared from biacetyl (3) in four reaction steps and in overall yields of 20% and 21%, respectively. They underwent a clean intramolecular 2 + 2] photocycloaddition upon irradiation at lambda = 350 nm. Whereas compound 2a reacted in the expected manner and yielded 7-oxabicyclo3.2.1.0(3,6)]octane 7 (87% yield), the regioselectivity in the photocycloaddition of compound 2b was completely reversed. The reaction led to compound 8 (92% yield) with the unusual 9-oxabicyclo4.2.1.0(3,8)]nonane skeleton, the structure of which was established by single-crystal X-ray crystallography. |
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