The directed ortho metalation - palladium catalyzed cross coupling connection. A general regiospecific route to 9-phenanthrols and phenanthrenes. Exploratory further metalation

Abstract

A new general and regiospecific synthesis of 9-phenanthrols (1 +2 [Formula: see text] 3 [Formula: see text] 4, Scheme 1, Table 1) proceeding by a Directed ortho Metalation (DoM), Suzuki-Miyaura cross coupling, and a new LDA-mediated Directed remote Metalation sequence is described. The facile Pd-catalyzed hydrogenolysis of the phenanthrols 4 into the corresponding phenanthrenes 5 via their triflates 18 translates the original DoM regioselectivity also into a general synthesis of phenanthrenes (Table 2). Further DoM (19 [Formula: see text]20, 21; 24 [Formula: see text]25), cross coupling (20c [Formula: see text]23), as well as oxidation - ring contraction (4b, 4f [Formula: see text]28a, 28b) chemistry of phenanthrene derivatives is reported.Key words: 9-phenanthrols, directed ortho metalation, Suzuki cross coupling, synthesis.