Synthesis of oxa-bridged derivatives from Diels–Alder bis-adducts of butadiene and 1,2,3,4-tetrahalo-5,5-dimethoxycyclopentadiene

• Faiz Ahmed Khan and
• Karuppasamy Parasuraman

Beilstein J. Org. Chem. 2010, 6, No. 64, doi:10.3762/bjoc.6.64

• ]. Previously, we reported a smooth one-pot transformation of norbornyl α-diketones to the corresponding oxa-bridged derivatives [7], but our initial attempts to transform the bis-diketones 7 and 9 to bis-oxa-bridged compounds 8 and 10 using this strategy did not give the desired result. However, when the

• analysis (Figure 1) [20]. Working backwards, the structures of the adduct 5, the bis-diketone 7 were confirmed unequivocally. We next turned our attention to the bromo analogue 1b in order to see if the overall yield of the bis-oxa-bridged derivatives 8 and 10 could be improved. We were also interested to

• yield. Ruthenium catalyzed oxidation of the bis-adducts followed by a one-pot transformation of the resulting α-diketone furnished oxa-bridged compounds. Unambiguous stereochemical assignments of both diastereomeric series are reported. Keywords: Diels–Alder reactions; diketones; oxa-bridged