Effect of carbenoid structure on the reactions of rhodium-stabilized carbenoids with cycloheptatriene

Davies, Huw M. L.; Stafford, Douglas G.; Hansen, Tore; Churchill, Melvyn Rowen; Keil, Kim M.

doi:10.1016/s0040-4039(00)00104-0

Cited by 43 publications

(39 citation statements)

References 9 publications

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“…15 In the cases where two new stereogenic centers were generated, the products 8a-h were formed with very high levels of diastereoselectivity (>30 : 1 dr) and enantioselectivity (≥96% ee). The isolated yields of the CHCR products 8 in some instances were moderate, because direct C–H insertion was a competing process.…”

Section: Substrate Scope Of the Chcr Reactionmentioning

confidence: 98%

“…15 In order to circumvent this problem, acyclic systems were examined in which the direct C–H insertion product would no longer be the thermodynamic product. This was accomplished by using allyl silyl ethers as substrates, because the direct C–H insertion product would be susceptible to a favorable siloxy-Cope rearrangement (Scheme 5).…”

Section: Substrate Scope Of the Chcr Reactionmentioning

confidence: 99%

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The Combined C–H Functionalization/Cope Rearrangement: Discovery and Applications in Organic Synthesis

2012

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Conspectus The development of methods for the stereoselective functionalization of sp3 C–H bonds is a challenging undertaking. This Account describes the scope of the combined C–H functionalization/Cope rearrangement (CHCR), a reaction that occurs between rhodium-stabilized vinylcarbenoids and substrates containing allylic C–H bonds. Computational studies have shown that the CHCR reaction is initiated by a hydride transfer to the carbenoid from an allyl site of the substrate, which is then rapidly followed by C–C bond formation between the developing rhodium-bound allyl anion and the allyl cation. In principle, the reaction can proceed through four distinct orientations of the vinylcarbenoid and the approaching substrate. The early examples of the CHCR reaction were all highly diastereoselective, consistent with a reaction proceeding via a chair transition state with the vinylcarbenoid adopting an s-cis conformation. Recent computational studies have revealed that other transition state orientations are energetically accessible, and these results have guided the development of highly stereoselective CHCR reactions that proceed through a boat transition state with the vinylcarbenoid in an s-cis configuration. The CHCR reaction has broad applications in organic synthesis. In some new protocols, the CHCR reaction acts as a surrogate to some of the classic synthetic strategies in organic chemistry. The CHCR reaction has served as a synthetic equivalent of the Michael reaction, the vinylogous Mukaiyama aldol reaction, the tandem Claisen rearrangement/Cope rearrangement, and the tandem aldol reaction/siloxy-Cope rearrangement. In all of these cases, the products are generated with very high diastereocontrol. With a chiral dirhodium tetracarboxylate catalyst such as Rh2(S-DOSP)4 or Rh2(S-PTAD)4, researchers can achieve very high levels of asymmetric induction. Applications of the CHCR reaction include the effective enantiodifferentiation of racemic dihydronaphthalenes and the total synthesis of several natural products: (−)-colombiasin A, (−)-elisapterosin B, and (+)-erogorgiaene. By combining the CHCR reaction into a further cascade sequence, we and other researchers have achieved the asymmetric synthesis of 4-substituted indoles, a new class of monoamine reuptake inhibitors.

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Section: Substrate Scope Of the Chcr Reactionmentioning

confidence: 98%

Section: Substrate Scope Of the Chcr Reactionmentioning

confidence: 99%

The Combined C–H Functionalization/Cope Rearrangement: Discovery and Applications in Organic Synthesis

2012

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“…The direct C-H insertion product 129 was subsequently found to be the more thermodynamically stable product, 165,178 meaning that the reaction likely proceeds via a highly concerted, ordered transition state 131 (Figure 20), as opposed to a two-step reaction.…”

Section: Scheme 23mentioning

confidence: 99%

Catalytic asymmetric C–H insertion reactions of α-diazocarbonyl compounds

2010

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“…However, the C -H insertion product is the thermodynamically more stable, since the system rearranged to the formal C -H insertion product upon heating [231] . Therefore, a combined C -H activation/Cope rearrangement is believed to occur in which the C -H activation process is interrupted cycloheptatrienes, insertion also occured very effectively in 91 -95% ee [207] . The reaction has been extended to include other donor/acceptor systems such as methyl phenyldiazophosphonate system 144 (Scheme 4.39 ).…”

Section: The Combined C -H Activation/cope Rearrangement Allylic C -Hmentioning

confidence: 99%

Asymmetric Synthesis through C–H Activation

Davies

Hansen

2010

Catalytic Asymmetric Synthesis

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Effect of carbenoid structure on the reactions of rhodium-stabilized carbenoids with cycloheptatriene

Cited by 43 publications

References 9 publications

The Combined C–H Functionalization/Cope Rearrangement: Discovery and Applications in Organic Synthesis

The Combined C–H Functionalization/Cope Rearrangement: Discovery and Applications in Organic Synthesis

Catalytic asymmetric C–H insertion reactions of α-diazocarbonyl compounds

Asymmetric Synthesis through C–H Activation

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