Directed Ortho Metalation Methodology. TheN,N-Dialkyl ArylO-Sulfamate as a New Directed Metalation Group and Cross-Coupling Partner for Grignard Reagents

Abstract

[reaction: see text] The ortho metalation (RLi/THF/-93 degrees C) of 3 followed by quench with a variety of electrophiles constitutes a new general route to substituted aryl O-sulfamates 4a-k. The Kumada-Corriu cross-coupling of O-sulfamates 4e, 4n-s, and 6a with Grignard reagents gives biaryls 9a-m, and the use of 2-halo and boron derivatives 4h, 4i, and 4k for Suzuki-Miyaura cross-coupling and generation of benzynes leads to naphthols 7a and 7b. A relative metalation ranking of the OSONEt(2) is reported.

Well-defined nickel and palladium precatalysts for cross-coupling

“…The utility of Ni precatalysts in coupling aryl sulfamates after directed ortho -metallation was described by the Snieckus group 156 in 2005. In this pioneering work, [(IMes)Ni(Cp)Cl] was used to form biaryls from phenyl sulfamates and arylmagnesium bromides.…”

Transition metals in organic synthesis: Highlights for the year 2005

“…Neopentyl arenesulfonates were used in place of aryl halides in cross-coupling reaction with alkyl magnesium bromides [97]. Nickel catalyzed couplings of aryl O-sulfamates with Grignard reagents [98,99].…”

Bench‐Stable N‐Heterocyclic Carbene Nickel Precatalysts for C−C and C−N Bond‐Forming Reactions

“…In order to combat this sensitivity, a number of researchers have investigated various strategies11 including the formation of stable nickel(II) complexes. Nolan12 and Snieckus13 independently demonstrated in 2005 the use of Cowley's η 5 ‐cyclopentadienyl NHC‐complex 1 14 (Scheme 1 a) as an effective, bench‐stable Ni‐precatalyst for aryl aminations and Kumada cross‐couplings, respectively. Matsubara also demonstrated the use of NHC‐phosphine Ni‐precatalyst 2 for Kumada cross‐couplings in 2006 15.…”