Salt‐Stabilized Silylzinc Pivalates for Nickel‐Catalyzed Carbosilylation of Alkenes

Abstract

We herein report the preparation of solid and salt‐stabilized silylzinc pivalates from the corresponding silyllithium reagents via transmetalation with Zn(OPiv)2. These resulting organosilylzinc pivalates show enhanced air and moisture stability and unique reactivity in the silylative difunctionalization of alkenes. Thus, a practical chelation‐assisted nickel‐catalyzed regioselective alkyl and benzylsilylation of alkenes has been developed, which provides an easy method to access alkyl silanes with broad substrate scope and wide functional group compatibility. Kinetic experiments highlight that the OPiv‐coordination is crucial to improve the reactivity of silylzinc pivalates. Furthermore, late‐stage functionalizations of druglike molecules and versatile modifications of the products illustrate the synthetical utility of this protocol.

Stereoselective C–O Silylation and Stannylation

“…Thereafter, we tested their reactivity for the cobalt-catalyzed silylation and stannylation of alkenyl acetates via C-O bond-activation (Figure 2). To our delight, CoBr 2 in the presence of 2,2'-bipyridyl enables silylation of 3a using Me 2 PhSi-ZnOPiv•Li 2 (Cl)(OPiv) (1a) as the nucleophile [PhMe 2 Si-ZnOPiv•2Li(OPiv) (Cl) was abbreviated as Me 2 PhSi-ZnOPiv for the sake of clarity], which displayed unique reactivity in carbonsilylation of alkenes by nickel catalysis, [45] the desired product 4 was obtained in 72% yield. Interestingly, the typical halides-supported Si-Zn reagents 1b-1d, as well as Si-Mg reagent 1e failed to undergo the C-O silylation process under the identical cobalt catalysis.…”

“…Organozinc reagents are of great important intermediates which display high reactivity and excelleng chemoselectivity in organic synthesis. [38][39][40][41][42][43][44] Hence, we were attracted to developing the well-activated silyl and stannyl zinc reagents via transmetalation of the corresponding lithium reagents, [45][46] and subsequently devising 3d cobaltcatalyzed cross-couplings [47][48][49][50][51][52][53] with polyfunctionalized alkenyl acetates to build synthetically useful C-Si [54][55][56] and C-Sn [57][58][59][60] bonds via umpolung strategy (Figure 1d). In this work, Me 2 PhSi-ZnOPiv•Li 2 (Cl) (OPiv) and ( n Bu) 3 Sn-ZnCl•LiCl show superior reactivity than the other Si-and Sn-based organometallic reagents.…”

Versatile OPiv-Supported Organozinc Reagents for Transition-Metal-Catalyzed Cross-Couplings

“…[36] Therefore, we recently developed a new type of solid silylzinc reagents R3Si-ZnOPiv (35) via OPiv-coordination instead of halides by transmetalation reaction of the corresponding silyl lithium with stoichimetric Zn(OPiv)2, which showed improved air and moisture stability (Scheme 7b). [37] Scheme 8. Representative examples for regioselective carbosilylation.…”

“…Thus far, the shortcomings of silylzinc halides, including difficulty in handling and poor reactivity were well improved by our operationally simple OPivcoordination on the silylzinc reagents. [37]…”

Directed, nickel-catalyzed 1,2-alkylsulfenylation of alkenyl carbonyl compounds

“…While 1,2-dicarbofunctionalization 13–15 has been extensively studied, 1,2-carboheterofunctionalization remains less explored and is largely limited to transformations introducing metalloid (semimetal) elements, namely borylative and silylative functionalizations, where the new C–B(Si) bond is formed via migratory insertion. 16 For non-metal elements (N, S, Se, etc. ), C–heteroatom bond formation is challenging, often requiring reductive elimination to take place from a high-valent Ni( iii ) intermediate.…”