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In J. Org. Chem., Vol. 37, page 673 (1972), E. L. Stogryn describes the preparation of 2,2-difluorobenzo-1,3-dioxole-5-carbaldehyde by formylation of 2,2-difluorobenzo-1,3-dioxol-5-yllithium with dimethylformamide. The lithium compound is obtained by reaction of 1 mole 5-bromo-2,2-di-fluorobenzo-1,3-dioxole with 1.3 mole butyllithium. Ortho-metallation is not mentioned by Stogryn, although butyllithium was applied in 30% excess. S. Cabiddu et al. describe in Journal of Organometallic Chemistry 136 139-146 (1977) two competitive reactions which occur by the treatment of 1,3-benzodioxole in hexane with n-butyllithium in dietbyl ether/hexane at -10° C. After carbonation of the reaction mixture the authors detected the formation of 1,3-benzodioxole-4-carbonic acid, originated from the 4-lithium compound with a yield of 41% and in addition thereto pyrocatechol and n-nonane, as a result of cleavage of the ether bond with a yield of each 45% of theory.