On the regioselectivity of the intramolecular [2 + 2]-photocycloaddition of alk-3-enyl tetronates

Roland Weixler, Jörg P. Hehn, Thorsten Bach

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16 Scopus citations

Abstract

The simple diastereoselectivity and the regioselectivity of the [2 + 2]-photocycloaddition of alk-3-enyl tetronates were studied, depending on the nature of the substituent R in the α-position. Fourteen tetronates were synthesized and their intramolecular photocycloaddition reactions performed. If R was an alkoxycarbonyl group and if the olefin, which underwent the intramolecular addition, was sterically congested, crossed photoproducts prevailed and were formed in yields between 35 and 65%. In all other cases, the straight photoproducts were obtained as the main reaction products in yields ranging from 39 to 84%. The structures of the photochemical products were thoroughly investigated by one- and two-dimensional NMR experiments. In all cases, the diastereoselectivitiy was excellent and only a single diastereoisomer was formed. A mechanistic model is proposed, which explains the regioselectivity of the [2 + 2]-photocycloaddition reaction.

Original languageEnglish
Pages (from-to)5924-5935
Number of pages12
JournalJournal of Organic Chemistry
Volume76
Issue number15
DOIs
StatePublished - 5 Aug 2011

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