Copper Catalysis for Synthesizing Main-Group Organometallics Containing B, Sn or Si

Abstract

A copper complex has proven to be a potent catalyst for forming a C–B bond via diborylation of arynes and alkynes, affording vic‐diborylarenes and vic‐diborylalkenes with high efficiency. A boryl‐substituted organocopper species, which is intermediately generated in the diborylation, has been found to be captured by a tin or a carbon electrophile, leading to three‐component borylstannylation or carboboration, in which C–B and C–Sn (or C) bonds are constructed simultaneously. Furthermore, reducing the Lewis acidity of the boron center with 1,8‐diaminonaphthalene decisively alters the regiochemical behavior of the borylcopper species, enabling the installation of a boryl moiety to occur at an internal carbon of terminal alkynes in borylstannylation and protoboration. Copper catalysis for C–Sn and C–Si bond‐forming processes via distannylation, hydrostannylation and silylstannylation, as well as silver catalysis for a C–B bond‐forming reaction, is also described.

Copper-Catalyzed Borylstannylation of Alkynes with Tin Fluorides

“…In particular, much attention has thus far been focused on the reaction of alkynes, which provides regio- and stereodefined vic -boryl­(stannyl)­alkenes, owing to the potential utility for accessing diverse multisubstituted alkenes of biological and pharmacological significance . Within this context, we have already developed the copper-catalyzed three-component borylstannylation of alkynes using bis­(pinacolato)­diboron ((pin)­B–B­(pin)) and tin alkoxides, where a copper alkoxide acts as a key catalytic species. , Although a variety of vic -boryl­(stannyl)­alkenes are efficiently accessible by this reaction, terminal alkynes, especially aliphatic ones, turned out to give the respective products only in moderate yield (Scheme ), which is ascribed to the formation of alkynylstannanes and a distannane as byproducts.…”

“…6 Within this context, we have already developed the copper-catalyzed threecomponent borylstannylation of alkynes 1f using bis-(pinacolato)diboron ((pin)B−B(pin)) and tin alkoxides, where a copper alkoxide acts as a key catalytic species. 7,8 Although a variety of vic-boryl(stannyl)alkenes are efficiently accessible by this reaction, terminal alkynes, especially aliphatic ones, turned out to give the respective products only in moderate yield (Scheme 1), which is ascribed to the formation of alkynylstannanes and a distannane 9 as byproducts.…”

Borylation and Stannylation Reactions with Tuning of Lewis Acidity

“…On the other hand, since organotrialkylstannanes, used mainly as stannylating reagents in this study, basically exhibit little Lewis acidity, we have been interested in increasing the tin-Lewis acidity by electron-withdrawing inductive effect of organic groups on tin center, thus leading to unique reactivities and stannylation reactions therewith. This paper aims to summarize our recent research on catalytic borylation/stannylation reactions since our last personal account in 2016, [6] and on their application to carbon-carbon bond-forming processes, focusing mainly on influential diminishment and increment of metal-Lewis acidity.…”

Radical Silyl‐ and Germylzincation of Propargylic Alcohols

“…The prevalence of carbon=carbon double bonds in organic molecules makes the stereodefined construction of multi‐substituted alkenes a central issue in organic synthesis [1,2] . In this context, the addition of element−metal bonds across carbon≡carbon triple bonds, i. e ., alkyne elementometalation reactions, as coined by Negishi , [3] is an area of intense on‐going research as it offers the possibility to prepare in a single operation 1,2‐difunctionalized alkenes ideally suited for the subsequent orthogonal introduction of two different substituents [4–7] . However, the success of this approach is heavily dependent on the regio‐ and the stereoselectivity of the addition reaction.…”