1. Condensed thiophenes from sulfur bridging. I. Phenanthro[4,5-bcd]thiophene
2. L. H. Klemm and J. J. Karchesy, J. Hetero-cyclic Chem., in press.
3. Über das
lin.
‐Dibenzothionaphthen im Steinkohlenteer
4. Comparison should be made with the paper by Campaigne and Osborn (8), who synthesized all of the three possible isomeric benzonaphthothiophenes and their sulfones, reported melting points: 4, 160.5-161°; 4-sulfone, 267-268°; 5, 182-184°; 5-sulfone, 232-234°; 7, 101.5-102°; 7-sulfone, 228-229°. The melting point of the Kruber and Rappen sulfone (designated A here) indicates that these workers isolated either 5-sulfone or (after preliminary rearrangement 3→6) 7-sulfone. Since some unreacted 3 was recovered, it seems unlikely that skeletal rearrangement occurred in their experiment. In an effort to establish the structure of A, Kruber and Rappen treated 8 with phosphorus penta-sulfide to yield 4(m.p. 160° ). Since oxidation of 4 gave sulfone B (m.p. 264°), different from A, these workers surmised, again probably erroneously, that B was a byproduct and that A remained in the mother liquor. The proposal (6) that a chrysene fraction of coal tar was found to contain 4 because it formed sulfone A must be considered incorrect. In a later paper, Kruber and Grigoleit (9) isolated from a coal-tar pyrene fraction a compound melting at 185°, to which they assigned, apparently correctly, structure 5. This compound was desulfurized to 3, but, surprisingly, was not converted into its sulfone (See also footnote 22).
5. Preparation and ultraviolet absorption spectra of the isomeric naphthobenzothiophenes and naphthobenzofurans