%0 Journal Article %A Weixler, Roland %A Hehn, Jörg P. %A Bach, Thorsten %D 2011 %T On the Regioselectivity of the Intramolecular [2 + 2]-Photocycloaddition of Alk-3-enyl Tetronates %U https://acs.figshare.com/articles/journal_contribution/On_the_Regioselectivity_of_the_Intramolecular_2_2_Photocycloaddition_of_Alk_3_enyl_Tetronates/2625586 %R 10.1021/jo201066d.s001 %2 https://acs.figshare.com/ndownloader/files/4276242 %K alkoxycarbonyl group %K substituent R %K photoproduct %K regioselectivity %K intramolecular photocycloaddition reactions %K NMR experiments %K reaction products %K yield %K tetronate %K intramolecular addition %X 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. %I ACS Publications