Cobalt-Catalyzed Cross-Couplings of Bench-Stable Alkynylzinc Pivalates with (Hetero)Aryl and Alkenyl Halides

Abstract

A catalytic system consisting of CoCl·2LiCl and TMEDA enables the cross-coupling of various electron-poor aryl and heteroaryl halides with various alkynylzinc pivalates. Coupling with alkenyl halides proceeds with retention of configuration.

Cobalt-Catalyzed Diastereoselective Cross-Couplings between Alkynylzinc Pivalates and Functionalized Cyclic Iodides or Bromides

“…9 Also, these organozinc pivalates undergo convenient cobalt-catalyzed cross-couplings with aryl halides and heteroaryl halides. 10 Herein, we report a new, diastereoselective cross-coupling between alkynylzinc pivalates of type 1 and various functionalized cyclic iodides or bromides of type 2. In preliminary experiments, 3-isopropylcyclohexyl iodide (2a) was treated with 2-phenylethynylzinc pivalate (1a) at 0 °C under various conditions (Table 1).…”

“…After solvent evaporation, solid organozinc pivalates are obtained with enhanced air and moisture stability . Also, these organozinc pivalates undergo convenient cobalt-catalyzed cross-couplings with aryl halides and heteroaryl halides . Herein, we report a new, diastereoselective cross-coupling between alkynylzinc pivalates of type 1 and various functionalized cyclic iodides or bromides of type 2 .…”

Construction of C(sp2)–X (X = Br, Cl) Bonds through a Copper-Catalyzed Atom-Transfer Radical Process: Application for the 1,4-Difunctionalization of Isoquinolinium Salts

“…On the other hand, alkenyl halides have served as versatile synthesis precursors in different cross-coupling reactions . The introduction of a carbon–halogen bond at the C-4-position of isoquinoline derivatives provides an important application prospect in organic synthesis.…”

Preparation and Reactions of Mono- and Bis-Pivaloyloxyzinc Acetylides

“…Recently, we have reported the preparation of a new class of zinc organometallics with the general formula RZnX·Mg­(OPiv) 2 · n LiCl (X = Cl, Br; abbreviated as RZnOPiv) . The nature of the organic group R can be an aryl, heteroaryl, benzyl, alkynyl, allyl, or amide enolate zinc pivalate . The presence of Mg­(OPiv) 2 within these zinc reagents confers then enhanced air and moisture stability .…”

“…The presence of Mg­(OPiv) 2 within these zinc reagents confers then enhanced air and moisture stability . For instance, alkynylzinc pivalates tolerate a broad range of functionalities and represent a reactive class of versatile C sp -centered nucleophiles that are stable for several hours when exposed to air. Herein, we wish to report the preparation and reactivity of two new alkynylzinc pivalates, namely mono-pivaloyloxyzinc acetylide ( 1 ) and bis-pivaloyloxyzinc acetylide ( 2 ), as storable solids with appreciable air and moisture stability (see Scheme ).…”