(a) We described previously some routes to prepare pyridazino-psoralens with the pyridazine ring attached to the furan nucleus in the tetracyclic compound J.C. González-Gómez, L. Santana, and E. Uriarte Synthesis 2002 43 46
To see a recent example where a selective oxidation of a dihydrobezofuran ring was accomplished with DDQ in a molecule that also contains a cyclohexene ring J.J. Chambers, J.C. Parrish, N.H. Jensen, D.M. Kurrasch-Orbaugh, D. Marona-Lewicka, and D.E. Nichols J. Med. Chem. 46 2003 3526 3535
A five step procedure to benzodifuran 7 from 5-bromo-6-methoxybenzofuran was described
A five step procedure to benzodifuran 7 from 5-bromo-6-methoxybenzofuran was described in: L.R. Worden, A.W. Burgstahler, K.D. Kaufman, J.A. Weis, and T.K. Schaaf J. Heterocycl. Chem. 6 1969 191 198
Personal communication Address: Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy and Pharmacal Sciences, Purdue University.
Personal communication of David E. Nichols, Address: Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy and Pharmacal Sciences, Purdue University.
A related reduction of pyridine derivatives with sodium cyanoborohydride to the corresponding 1,4-dihydropyridines, was previously reported: U. Eisner, and E. Booker J. Chem. Soc. Perkin Trans. 1 1975 929 931