This paper describes the synthesis of an unsubstituted heterocyclic asymmetric triptycene, 5,12-dihydro-5,12-[2',3'-6]thienonaphthacene (8). The choice of the starting materials in this synthesis, naphtho [2,3-6]thiophene (5) and 1,4-epoxy-l,4-dihydronaphthalene (6), is based in part on Hückel molecular orbital computations and in part on experimental data.Triptycene (l)1,a has a rigid "propeller" structure and Csh symmetry. Triptycenes are asymmetric when every one of the three aromatic rings is unlike the other two. This asymmetry can be achieved by attaching substituents at appropriate positions, as done by Ogura (2),3,4 or by having every ring inherently different from the other two. An example of

Arylmalonic esters and arylmalonodinitriles can be coupled oxidatively to the corresponding bibenzyls. Good yields of dimers are obtained when a para substituent (CH3, Cl) is introduced, which inhibits the formation of higher oligomers through benzylic C-para C coupling. Substitution at both ortho positions and the para position (CH3) in phenylcyanoacetic esters completely inhibits C-C coupling by steric crowding. Ketene imines are formed instead by C-N coupling. Substitution at one ortho position (CHa) partially gives the usual C-C coupling together with benzylic C-para C coupling (oligomer formation) in case of a free para position and C-N coupling (ketene imine formation) in case of a CHs-substituted para position. The thermal dissociation of the dimers into radicals is confirmed by esr analysis. From nmr line width measurements kinetic parameters for the dissociation reaction are obtained.

When the dialdehydes I and I11 are heated for 1 h in a refluxing ethanolic sodium cyanide solution in air, the quinones I1 and IV are formed in 50% and 72% yield, respectively.

60 MHz, using 30-35 mg of steroid per 0.6 ml of solvent, either CDCla or pyridine-ds, and TMS as internal standard. The methyl signals of the cholestane side chain a t C-21 and C-26,27 were centered a t 0.84 f 0.02 ppm, respectively, each with J = 6-8 cps for all compounds reported in both solvents. The assignment of these bands and the (2-19 signal was based on the coupling constants and the relative peak intensities. Mass spectra were determined on an Hitachi RMU-6B single-focusing mass spectrometer. ORD curves were recorded on a Jasco 5A spectropolarimeter. The authors are indebted to Dr. R. B. Treptow and to Procter and Gamble, Co., Miami Valley Laboratories, for the use of their spectropolarimeter.

Abstract-The mass spectra of %-labelled thiophenes were studied and the label-distributions for the C,H, @, HCS @, C,H2S @ and [M -CH,] @ ions are interpreted in terms of a carbon skeletal rearrangement. From a comparison of the results of 13C-labelling and D-labelling, a concurrent hydrogen migration process is demonstrated. The production of HCS @ ions is preceded by partial carbon scrambling and hydrogen migration is of minor importance. In contrast, hydrogen scrambling predominates over carbon scrambling in the loss of acetylene.