Cycloaddition of 9,10-dimethoxyanthracene (1) to tetrabromoacetone (2a) und
er a variety of conditions afforded isomers 3a,b; reductive debromination o
f 3a,b afforded 4, while reduction with NaBH4 gave alcohol 6 which on reduc
tive debromination gave olefin 7; reaction of 1 with 2b gave isomers 8a,b.