Regioselective 1,4-Silylcupration of 1,3-Dienes − Characterization and Electrophilic Trapping of the Intermediate (σ-Allyl)copper Complex

Abstract

Silylcupration reactions of 1,3‐dienes with a cyanocuprate reagent PhMe2SiCuCNLi produce a (4‐silyl‐2‐alken‐1‐yl)copper complex, which was trapped by electrophiles. The use of allylic phosphates as electrophiles resulted in highly regioselective reactions with overall 1,4‐addition of the silyl and allyl moieties across the diene. Water (H3O+) or acetyl chloride as the electrophile afforded a mixture of 1,2‐ and 1,4‐addition products, whereas carbon dioxide gave a highly regioselective 1,2‐addition. The intermediate (4‐silyl‐2‐alken‐1‐yl)copper complexes were characterized by NMR spectroscopy. The mechanism of the silylcupration reaction of 1,3‐dienes and subsequent electrophilic trapping is discussed. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Three-Component Ni-Catalyzed Silylacylation of Alkenes

“…Along Path A, direct which ultimately is trapped by the electrophile as shown in Path B (analogous to Cu-catalyzed processes). 17 Uncatalyzed addition of ClZnSiMe 2 Ph to styrene is unlikely because <2% conversion of alkene was observed in the absence of Ni-catalyst (Scheme 5B), which is consistent with prior reports. 17 This complex undergoes direct reaction with the acid chloride to generate the product and turnover the catalyst.…”

“…17 Uncatalyzed addition of ClZnSiMe 2 Ph to styrene is unlikely because <2% conversion of alkene was observed in the absence of Ni-catalyst (Scheme 5B), which is consistent with prior reports. 17 This complex undergoes direct reaction with the acid chloride to generate the product and turnover the catalyst. The mechanism for reaction of the alkyl-[Ni]-complex with the acid chloride may either proceed via direct addition or by an oxidative addition/reductive elimination sequence.…”

Three-Component Ni-Catalyzed Silylacylation of Alkenes

“…Along Path A, direct which ultimately is trapped by the electrophile as shown in Path B (analogous to Cu-catalyzed processes). 17 Uncatalyzed addition of ClZnSiMe 2 Ph to styrene is unlikely because <2% conversion of alkene was observed in the absence of Ni-catalyst (Scheme 5B), which is consistent with prior reports. 17 This complex undergoes direct reaction with the acid chloride to generate the product and turnover the catalyst.…”

“…17 Uncatalyzed addition of ClZnSiMe 2 Ph to styrene is unlikely because <2% conversion of alkene was observed in the absence of Ni-catalyst (Scheme 5B), which is consistent with prior reports. 17 This complex undergoes direct reaction with the acid chloride to generate the product and turnover the catalyst. The mechanism for reaction of the alkyl-[Ni]-complex with the acid chloride may either proceed via direct addition or by an oxidative addition/reductive elimination sequence.…”

Construction of C–Cu Bond: A Useful Strategy in CO2 Conversion

“…56 In 2002, the silylcupration of 1,3-dienes was reported by Backvall's group using cyanocuprate reagent PhMe 2 SiCuCNLi, in which a new (4-silyl-2-alken-1-yl)-copper complex, IM27, was detected (Scheme 25). 57 A tandem electrophilic trapping reaction of the resulting (σ-allyl)copper complex is then performed using different electrophiles, and it is found the regioselectivity of the trapping reaction depends strongly on the electrophile. With CO 2 as electrophile, a six-membered-ring transition state might be formed, giving the 1,2-addition product exclusively.…”

Catalyst Controlled Regiodivergent Arylboration of Dienes

“…It is important to note that this complex is formed exclusively as the Z -alkene isomer and is the formal 1,4-addition product of the IPrCuBpin across the diene. The formation of the Z -alkene may either be the result of a formation of thermodynamically more stable complex or a kinetically favored insertion to an s- cis -diene . To provide evidence that this complex is generated under the catalytic reaction conditions, it could be subjected to Pd–PAd 2 n -Bu G3 and PhBr to yield the expected 1,2-arylboration product 2 with high regioselectivity.…”

Three-Component Ni-Catalyzed Silylacylation of Alkenes

“…Along Path A, direct which ultimately is trapped by the electrophile as shown in Path B (analogous to Cu-catalyzed processes). 17 Uncatalyzed addition of ClZnSiMe 2 Ph to styrene is unlikely because <2% conversion of alkene was observed in the absence of Ni-catalyst (Scheme 5B), which is consistent with prior reports. 17 This complex undergoes direct reaction with the acid chloride to generate the product and turnover the catalyst.…”

“…17 Uncatalyzed addition of ClZnSiMe 2 Ph to styrene is unlikely because <2% conversion of alkene was observed in the absence of Ni-catalyst (Scheme 5B), which is consistent with prior reports. 17 This complex undergoes direct reaction with the acid chloride to generate the product and turnover the catalyst. The mechanism for reaction of the alkyl-[Ni]-complex with the acid chloride may either proceed via direct addition or by an oxidative addition/reductive elimination sequence.…”

Construction of C–Cu Bond: A Useful Strategy in CO2 Conversion

“…56 In 2002, the silylcupration of 1,3-dienes was reported by Backvall's group using cyanocuprate reagent PhMe 2 SiCuCNLi, in which a new (4-silyl-2-alken-1-yl)-copper complex, IM27, was detected (Scheme 25). 57 A tandem electrophilic trapping reaction of the resulting (σ-allyl)copper complex is then performed using different electrophiles, and it is found the regioselectivity of the trapping reaction depends strongly on the electrophile. With CO 2 as electrophile, a six-membered-ring transition state might be formed, giving the 1,2-addition product exclusively.…”

Catalyst Controlled Regiodivergent Arylboration of Dienes

“…It is important to note that this complex is formed exclusively as the Z -alkene isomer and is the formal 1,4-addition product of the IPrCuBpin across the diene. The formation of the Z -alkene may either be the result of a formation of thermodynamically more stable complex or a kinetically favored insertion to an s- cis -diene . To provide evidence that this complex is generated under the catalytic reaction conditions, it could be subjected to Pd–PAd 2 n -Bu G3 and PhBr to yield the expected 1,2-arylboration product 2 with high regioselectivity.…”

Three-Component Ni-Catalyzed Silylacylation of Alkenes

“…Along Path A, direct which ultimately is trapped by the electrophile as shown in Path B (analogous to Cu-catalyzed processes). 17 Uncatalyzed addition of ClZnSiMe 2 Ph to styrene is unlikely because <2% conversion of alkene was observed in the absence of Ni-catalyst (Scheme 5B), which is consistent with prior reports. 17 This complex undergoes direct reaction with the acid chloride to generate the product and turnover the catalyst.…”

“…17 Uncatalyzed addition of ClZnSiMe 2 Ph to styrene is unlikely because <2% conversion of alkene was observed in the absence of Ni-catalyst (Scheme 5B), which is consistent with prior reports. 17 This complex undergoes direct reaction with the acid chloride to generate the product and turnover the catalyst. The mechanism for reaction of the alkyl-[Ni]-complex with the acid chloride may either proceed via direct addition or by an oxidative addition/reductive elimination sequence.…”

Construction of C–Cu Bond: A Useful Strategy in CO2 Conversion

“…56 In 2002, the silylcupration of 1,3-dienes was reported by Backvall's group using cyanocuprate reagent PhMe 2 SiCuCNLi, in which a new (4-silyl-2-alken-1-yl)-copper complex, IM27, was detected (Scheme 25). 57 A tandem electrophilic trapping reaction of the resulting (σ-allyl)copper complex is then performed using different electrophiles, and it is found the regioselectivity of the trapping reaction depends strongly on the electrophile. With CO 2 as electrophile, a six-membered-ring transition state might be formed, giving the 1,2-addition product exclusively.…”

Catalyst Controlled Regiodivergent Arylboration of Dienes

“…It is important to note that this complex is formed exclusively as the Z -alkene isomer and is the formal 1,4-addition product of the IPrCuBpin across the diene. The formation of the Z -alkene may either be the result of a formation of thermodynamically more stable complex or a kinetically favored insertion to an s- cis -diene . To provide evidence that this complex is generated under the catalytic reaction conditions, it could be subjected to Pd–PAd 2 n -Bu G3 and PhBr to yield the expected 1,2-arylboration product 2 with high regioselectivity.…”