The structures of the aldehydes VI and XI11 were not established; however, the preferential formylation of benzo-l14-oxathiadiene (I) in the 2-position (I-tII) is considered convincing evidence for the assignment of structure XIII, and is also consistent with the significant difference in yield noted for the formylation of the 2-, and 3-methyl derivatives (5 and 27a/,, respectively). The syntheses employed for 2-and 3-methylbenzo-l, 4-oxathiadiene (I11 ...
