ChemInform Abstract: The Directed ortho Metalation - Cross-Coupling Symbiosis in Heteroaromatic Synthesis

Abstract

Thirty years after its discovery by Gilman and Wittig, the Directed ortho Metalation (DoM) reaction continues to march in synthetically useful paths. To offer evidence for this statement, this lecture review describes a new and general cumyl Directed Metalation Group (DMG) (Schemes 2–6) and a phosphine oxide DMG (Schemes 7 and 8). Aryl-aryl cross-coupling chemistry is highlighted by polymer support Suzuki-Miyaura (Schemes 10 and 11) and an aryl O-carbamate-Grignard of value in the construction of naphthalenes (Scheme 12) and indoles (Scheme 13) and, for the latter class of compounds, in the generation of 4,5-quinodimethane intermediates (Scheme 14) for the synthesis of corresponding annelated derivatives (Scheme 15). The marriage of DoM with the Negishi cross-coupling reaction is demonstrated in general (Scheme 16). The concept of Directed remote Metalation (DreM) (Schemes 17 and 19) is applied to the synthesis of dibenzopyranones (Scheme 18), xanthones (Scheme 21), acridones, dibenzoazepinones, and oxindoles (Scheme 20). In this context, a carbanionic N-to-ortho-C t-Boc migration leading to anthranilate esters is also achieved (Scheme 20). For provision of diaryl ethers, diaryl sulfides, and diaryl amines, a new copper catalyst is introduced into the venerable Ullmann reaction (Scheme 22) and its extension by DoM, and cross-coupling chemistry is indicated (Scheme 23). A recently evolving link to DoM, the Grubbs metathesis process is manifested in the total synthesis of two natural products (Schemes 25 and 26) and has anticipated use more broadly in heterocyclic synthesis. (Scheme 27).