Dehydroamination Reaction of 9-Amino-9,10-dihydrophenanthrene and Related Compounds by Thermolysis

Abstract

Dehydroamination of 9-alkylamino-9,10-dihydrophenanthrene occurred at 190—250 °C under non-basic conditions to give phenanthrene exclusively. The thermal reaction of cis-9-t-butylamino-10-methoxy-9,10-dihydrophenanthrene gave both 9-methoxyphenanthrene and 9-t-butylaminophenanthrene, while 9-aminophenanthrene was obtained from the thermal reaction of 9-amino-10-methoxy-9,10-dihydrophenanthrene. The thermal reaction of 9-amino-9,10-dihydroanthracene gave both anthracene and 9-aminoanthracene. Analysis of activation energies and frequency factors showed that the dehydroamination proceeds via an intramolecular proton transfer from C-10 to the amino group and subsequent C–N bond cleavage.

A Convenient Synthesis of Alkyl- and Dialkylphenanthren-9-ylamines

“…However, the most convenient routes are based upon the Curtius rearrangement of azides 7 and the Bischler-Napieralski cyclization of biphenyl acetamide derivatives. 2,8 More reliable methods involving the rearrangement of polycondensed triazolyl derivatives, 9 the transformation of spiro-fluorenetriazolines by electrochemical means, 10 the photochemically induced or radical-mediated cyclization of 1,2diarylaminoethylenes, 1,11 the dehydromethoxylation of aminomethoxydihydrophenanthrenes 12 have been also reported. However, all these synthetic routes suffer from several drawbacks and genuinely lack universality.…”