Phenanthrene Synthesis by Iron-Catalyzed [4 + 2] Benzannulation between Alkyne and Biaryl or 2-Alkenylphenyl Grignard Reagent

Abstract

The [4+2] benzannulation reaction of internal or terminal alkynes with 2-biaryl, 2-heteroarylphenyl, or 2-alkenylphenyl Grignard reagents in the presence of Fe(acac)(3), 4,4'-di-tert-butyl-2,2'-bipyridyl, and 1,2-dichloro-2-methylpropane takes place at room temperature in 1 h to give 9-substituted or 9,10-disubstituted phenanthrenes and congeners in moderate to excellent yields. The reaction tolerates sensitive functional groups such as bromide and olefin. When applied to a 1,3-diyne, the annulation reaction takes place on both acetylenic moieties to give a bisphenanthrene derivative.

2,2′‐Bis‐substituted Biphenyls by the Addition of Nucleophiles to Benzyne Followed by In Situ Oxidative Homocoupling

“…[26] The conditions introduced by Nakamura and co-workers [27] using [Fe-(acac) 3 ] with tetramethylethylenediamine (TMEDA) as ligand and dichloroisobutane (DCIB) as a stoichiometric oxidant provided 16 % of the desired product (entry 12, Table 1). The best yield (24 %) was obtained by using dilithium tetrachlorocuprate (CuLi 2 Cl 4 ) and dioxygen (entry 13, Table 1).…”

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

“…This is the first successful catalytic carbomagnesiation of dialkylacetylenes. Note that Ilies and Nakamura reported iron-catalyzed annulation reactions of various alkynes, including dialkylacetylenes with 2-biphenylylmagnesium reagents to form phenanthrene structures [113]. …”

Pd catalyzed insertion of alkynes into cyclic diaryliodoniums: a direct access to multi-substituted phenanthrenes

“…7c Recently, Nakamura reported that iron catalyzed [4+2] benzannulation between alkyne and 2-alkenylphenyl Grignard reagent. 8 Both of these two methods employed highly moisture sensitive organometallic reagents, increasing the difficulty to operate the reactions. Compared to linear diaryliodoniums that are widely reported as arylating reagents, 10 cyclic diaryliodoniums have advantages because their arylated products themselves incorporate the iodoarenes which are inevitably produced and often discarded in the arylation with linear diaryiodoniums.…”