Alkylation of Aryl N‐(2‐Pyridylsulfonyl)aldimines with Organozinc Halides: Conciliation of Reactivity and Chemoselectivity

Abstract

The best of both worlds: With a coordinating 2‐pyridylsulfonyl group as the N‐activating group, aromatic aldimines show unprecedented high reactivity towards the direct addition of alkyl zinc bromide reagents in the presence of catalytic amounts of Cu(OTf)2. The reaction combines high reactivity with wide functional‐group compatibility to provide ready access to functionalized benzylamines and derivatives (see example). Tf=trifluoromethanesulfonyl.

Regio‐ and Stereoselective Functionalization Enabled by Bidentate Directing Groups

“…(1) directing groups must be stable during the reactions and should not react with coupling partners, (2) directing groups need to be reversibly coordinated with catalysts, (3) directing groups must be easily installed and removed with a high functional group tolerance. Monodentate directing groups (DGs), such as amide, [5] ester, [6] carboxylic acid, [7] ketone, [8] heterocyclic, [9] amine, [10] sulfur, [11] imine, [12] phosphine, [13] and hydroxy [14] groups, have been explored in efforts to improve reactivity and regioselectivity. Uncontrolled regioselectivity and unexpected side reactions often occur owing to the weak coordination of the monodentate directing group.…”

Bis[μ-2-(aminosulfanyl)pyridine(1−)]bis[(η5-pentamethylcyclopentadienyl)iridium(III)] diiodide

“…For related organic compounds, see: Robinson & Hurley (1965); Brito et al (2002); Miura et al (2003). For related coordination compounds, see: Nakayama et al (1999); Esquivias et al (2007); Nanthakumar et al (1999); Ishiwata et al (2006); Arita et al (2008). For 2-pyridylmethylamido complexes showing the -2 N(py),N(NH):N(NH) bridging mode, see: Westerhausen et al (2002); Wong & Wong(2002).…”

“…In this complex the N-S and S-C bond lengths are 1.711 (3)-1.718 (3) and 1.742 (4)-1.747 (4) Å, respectively. Furthermore, a few crystal structures of metal complexes with 2-pyridinesulfonamide {(2-py)SO 2 NH 2 } derivatives have been reported (Esquivias et al, 2007;Nanthakumar et al, 1999) py)SNHligand has been characterized by X-ray methods. The Ir-N(py) bond length in compound (I) is 2.085 (9) Å, and the bridging Ir-N(NH) bond lengths are 2.110 (9) and 2.113 (9) Å.…”

PdII‐Catalysed CH Functionalisation of Indoles and Pyrroles Assisted by the Removable N‐(2‐Pyridyl)sulfonyl Group: C2‐Alkenylation and Dehydrogenative Homocoupling

“…Some mechanistic studies based upon intermolecular competition experiments and kinetic isotope effects have also been undertaken. For both types of transformation, the presence of a N-(2-pyridyl)sulfonyl [24] directing group proved to be crucial to ensuring high reactivity and complete regiocontrol. [25]…”