Various salicylaldehydes were treated with bromonitromethane in the presence of an inorganic base to give 2-nitrobenzo [b] furan derivatives, and the reaction mechanisms were investigated. The most remarkable feature of the reactions is that 3-hydroxysalicylaldehyde (1k) alone among various hydroxysalicylaldehydes (1b, k, n, r) gave 2-nitro-7-hydroxybenzo [b] furan in good yield. Bromonitromethane reacted with salicylaldehydes at the aldehyde group exclusively to give 1-(2-hydroxyphenyl)-2-bromo-2-nitroethanols (14), followed by cyclization to produce mixtures consisting of cis- and trans-2-nitro-3-hydroxy-2, 3-dihydrobenzo [b] furans (8a, b ; 9a, b ; 10a, b). The stereochemistry of these products is discussed on the basis of the spectral data and chemical reactivities. The intermediates, 2, 3-dihydrobenzo [b] furans, underwent dehydration smoothly to give 2-nitrobenzo [b] furans.