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IV-Methyl-lV-[4-(IV,lV-dimethylamino)-2-methylbenzyl]-JV,,jV '-dimethyl-4,4,-diamino-2,2,-dimethyldiphenylmethane (19): NMR (CC14) 2.11 (s, 6 H, ArCH3), 2.17 (s, 3 H, ArCHg), 2.74 (s, 3 H, NCH3), 2.77, 2.79 (2 s, 12 H, NCH3), 3.56 (s, 2 H, ArCH2Ar), 4.17 (s, 2 H, NCH2Ar), 6.10-6.90 (m, 9 H, aromatic protons); IR (film) 3000-2800 (s), 1620 (vs), 1515 (vs), 1480 (m), 1450 (m), 1350 (s), 805 (s), 780 (w), 760 (w), 705 (vw), 695 (vw) cm'1; mol wt of C28H37N3, 415.62; mass spectrum (70 eV),

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22) Bicyclohexyl appeared to be absent.10 Cyclohexene in small amounts could have escaped detection, but since disproportionation and combination are about equal23 it seems unlikely that any significant amount was formed. (23) W. A. Cramer, J.

The synthesis of the title compounds l a and Ib is described. Starting from the corresponding 1,2-dimethylenecycloalkanes 6, the compounds 1 were obtained in four steps, viz. addition of dichlorocarbene, reduction with triphenyltin hydride, treatment with potassium tert-butoxide and silver-ion-catalyzed rearrangement. In the last step, the 1,2-isomers 11 of 1 were also formed, and their thermal rearrangement to the benzocycloalkenes 4 is briefly described. Compound Ib rearranged to its aromatic isomer [6]paracyclophane (2b) both thermally (60°C in solution, 100-460" C flow pyrolysis) and under silver-ion catalysis at room temperature; in this latter reaction, the initially formed 2b was gradually further isomerized to 4b. At higher temperatures, 2b rearranged to the spirotrienes 3b and finally fragmented to give p-ethylstyrene (17). From l a , the spirotriene 3a and benzocycloheptene (4a) were obtained by thermolysis and by silver-ion catalysis, respectively. The mechanism of these reactions is discussed and it is concluded that [5]paracyclophane (2a) is a transient intermediate in the reaction of la. 'I.