Transition-metal catalyzed silylmetalation of allenes

Silicon‐ and tin‐containing molecules are versatile building blocks in organic synthesis. A stalwart method for their preparation relies on the stoichiometric use of silicon‐ and tin‐based cuprates, although a few copper(I)‐catalyzed or even copper‐free protocols have been known for decades. In this Concept, we describe our efforts towards copper(I)‐catalyzed carbonsilicon and also carbontin bond formations using soft bis(triorganosilyl) and bis(triorganostannyl) zinc reagents as powerful sources of nucleophilic silicon and tin. Conjugate addition, allylic substitution, and carboncarbon multiple bond functionalization is now catalytic in copper!

Section: Conjugate Additionmentioning

confidence: 99%

“…With the chemistry of (R 3 Si) 2 Zn unexplored, we set out to examine the generation of (R 3 Si) 2 Zn32–34 and that of the related (R 3 Sn) 2 Zn35, 36 (Scheme ). For this, corresponding R 3 SiCl and R 3 SnCl are treated with lithium to form R 3 SiLi and R 3 SnLi,31 respectively.…”

Section: Conjugate Additionmentioning

confidence: 99%

Silicon‐ and Tin‐Based Cuprates: Now Catalytic in Copper!

Weickgenannt

Oestreich

2009

“…Silicon‐based cuprates such as Fleming’s (Me 2 PhSi) 2 CuLi ⋅ LiX or Me 2 PhSiCu ⋅ LiX (X=I or CN) are, despite being stoichiometric in copper(I), established reagents for the formation of carbon – silicon bonds 1. Catalytic variants had been elusive for decades2 until our laboratory introduced (Me 2 PhSi) 2 Zn ⋅ 4 LiCl3 as a pronucleophile in copper(I) catalysis 4. Combinations of (Me 2 PhSi) 2 Zn ⋅ 4 LiCl and CuX are broadly applicable to common acceptors [5 – 8] but rendering these copper(I)‐catalyzed reactions asymmetric poses a formidable challenge.…”

Section: Methodsmentioning

confidence: 99%

Asymmetric Catalysis with Silicon‐Based Cuprates: Enantio‐ and Regioselective Allylic Substitution of Linear Precursors

Hensel

Oestreich

2015

An enantio- and regioselective allylic silylation of linear allylic phosphates that makes use of catalytically generated cuprate-type silicon nucleophiles is reported. The method relies on soft bis(triorganosilyl) zincs as silicon pronucleophiles that are prepared in situ from the corresponding hard lithium reagents by transmetalation with ZnCl2 . With a preformed chiral N-heterocyclic carbene-copper(I) complex as catalyst, exceedingly high enantiomeric excesses are achieved. The new method is superior to existing ones using a silicon-boron reagent as the source of the silicon nucleophile.

“…Although transition-metal-catalyzed addition of a nonanionic silyl reagent to alkenes, for example, in hydrosilylation, [1] bis-silylation, [2] silylstannylation, [3] and silylboration, [4] is relatively facile and well-developed, addition of an anion-ic silyl reagent, such as silylcopper and silylzinc complexes, to alkenes has been difficult, due mainly to the low reactivity of alkenes. Indeed, there are plenty of examples of silylmetalation of alkynes, [5][6][7][8][9][10][11] allenes, [12,13] and 1,3-dienes, [14,15] but few in the case of alkenes. Carbometalation is also of great interest, and much effort has been directed towards this tough task, although the situation is much the same as with silylmetalation.…”

Section: Introductionmentioning

confidence: 99%

Silylmetalation of Alkenes

Nakamura

Yonehara

Uchiyama

2008

Silylmetalation of alkenes is challenging due to the low reactivity of the substrates. In contrast, carbometalation of alkenes has been realized through several innovative methods, including activation of the reagent and the substrate. A similar approach could be applicable to silylmetalation of alkenes, and we have recently developed a bimetal activation method using zincate complexes for this purpose. Here, we describe how the silylzincation of alkenes was achieved. First, the strategies for carbometalation of alkenes will be summarized. Secondly, the history and development of silylzincation chemistry are briefly described. Then the details of our findings related to two types of silylzincation of alkenes, as well as recent progress in mechanistic studies, are discussed. The key point in the silylzincation of alkenes proved to be the bimetal activation of the substrate. One metal (copper or titanium) strongly coordinates and activates the alkene moiety, and the other metal (zinc) acts as the electron acceptor from the silyl group by way of the alkene moiety. This dual activation concept is expected to be applicable to other combinations of metals, as well as to new types of reactions.