Beilstein J. Org. Chem.2010,6, No. 76, doi:10.3762/bjoc.6.76
; quinonemonoacetals; Introduction
The behaviour of excited 1,2- and 1,4-quinones towards ground-state molecules differs greatly. Whereas the former typically react via H-abstraction by an excited carbonyl group [1], the latter smoothly undergo [2 + 2] cycloaddition to alkenes to afford cyclobutane-type
PDF
Graphical Abstract
Scheme 1:
Synthesis of 2a,8b-dihydrocyclobuta[a]naphthalene-3,4-diones.
Beilstein J. Org. Chem.2008,4, No. 15, doi:10.3762/bjoc.4.15
regioselectivity was not affected in the reaction in the presence of a catalytic amount of BF3 · OEt2 (entry 7).
We next turned to the use of quinonemonoacetals 13 and 14 as dienophiles [36]. No adduct was formed on reaction of 13 in CH2Cl2 without a catalyst at room temperature (rt) (entry 8), whereas refluxing