Regiospecific synthesis of alkylphenanthrenes using a combined directed ortho and remote metalation – Suzuki–Miyaura cross coupling strategy

Abstract

Using a combined directed ortho metalation (DoM) – Suzuki–Miyaura cross coupling – directed remote metalation (DreM) approach, the alkylphenanthrenes (APs) 1-methyl- (5a), 1,7-dimethyl- (5b), 2,7-dimethyl- (5c), 7-ethyl-1-methyl- (15), and 7-tert-butyl-1-methylphenanthrenes (27) have been synthesized in four to seven steps and 21%–36% overall yields. In contrast to classical protocols, this method, which may be scaled to gram quantities, provides single isomers of APs in high purity of value as analytical standards for environmental studies. Aminocarbonylation of triflates to N,N-diethylbenzamides (9 [Formula: see text] 10) and anionic Fries rearrangement (23 [Formula: see text] 24) provide other potential links to DoM chemistry.Key words: phenanthrene, directed ortho metalation, Suzuki–Miyaura cross coupling, synthesis, polycyclic aromatic hydrocarbon, carbonylation.