Rh(iii)-catalyzed C–H activation/cycloaddition of benzamides and methylenecyclopropanes: divergence in ring formation

Cui, Sunliang; Zhang, Yan; Wu, Qifan

doi:10.1039/c3sc51424b

Cited by 209 publications

(86 citation statements)

References 101 publications

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“…9,10 On the other hand, the β-C elimination from intermediate I, generating an 8-membered rhodacycle likes II, should be favorable by releasing of the ring strain of the cyclopropane moiety. 11 Besides, the ring-opening of cyclopropene by activation of the π bond was implied in literatures, 7,12 whether such a process could compete with the C-H activation under Cp*Rh(III) catalysis is unknown. In addition, while the concept of external oxidant-free C-H activations becomes more and more 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 popular, 13,14,15 how the O-NHAc moiety in N-phenoxyacetamides works as an internal oxidant is still unclear.…”

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confidence: 98%

“…Geometries for Key Stationary Points in Reactions of B in Figure 3 (All Hydrogen Atoms are Hidden for Clarity; Selected Distances are in Angstrom).Although the above Rh(III)/Rh(V) mechanism looks quite reasonable for 2H-chromene formation, the opening of the three-membered ring prior to the O-N bond cleavage from B-IN4 should be evaluated 11. Indeed, the energy profile inFigure 5shows that the β-carbon elimination via B-TS8 is 5.2 kcal/mol more favorable kinetically thanthe Rh(V)-nitrenoid formation via B-TS4 (Figure 3), and the formation of B-IN10 is irreversible as the energies of the following transition states are much lower than that of B-TS8.…”

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confidence: 99%

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Mechanistic Understanding of the Divergent Reactivity of Cyclopropenes in Rh(III)-Catalyzed C–H Activation/Cycloaddition Reactions of N-Phenoxyacetamide and N-Pivaloxybenzamide

Guo

Xia

2015

J. Org. Chem.

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Density functional theory calculations were conducted to develop a mechanistic understanding of the Rh(III)-catalyzed C-H activation/cycloaddition reactions of N-phenoxyacetamide and N-pivaloxybenzamide with cyclopropenes, and insights into the substrate-dependent chemoselectivity were provided. The results showed that the divergence originated from the different reactivity of the seven-membered rhodacycles from the insertion of cyclopropene into the Rh-C bond. In reactions of N-pivaloxybenzamide, such an intermediate undergoes the pivalate migration to form a cyclic Rh(V)-nitrenoid intermediate in a reaction that is easier than the opening of the three-membered ring by β-carbon elimination, leading finally to a tricyclic product with retention of the cyclopropane moiety by facile reductive elimination. While similar Rh(V)-nitrenoid species could also be possibly formed in Cp*Rh(III)-catalyzed reactions of N-phenoxyacetamide, the β-carbon elimination occurs more easily from the corresponding seven-membered rhodacycle intermediate and the subsequent O-N bond cleavage gives rise to an unexpected dearomatized (E)-6-alkenylcyclohexa-2,4-dienone intermediate. The E/Z isomerization of this intermediate is required for the final cyclization to 2H-chromene, and interesting metal-ligand cooperative catalysis with Rh(III) carboxylate was disclosed in the C═C double bond rotation process.

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confidence: 98%

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confidence: 99%

Mechanistic Understanding of the Divergent Reactivity of Cyclopropenes in Rh(III)-Catalyzed C–H Activation/Cycloaddition Reactions of N-Phenoxyacetamide and N-Pivaloxybenzamide

Guo

Xia

2015

J. Org. Chem.

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“…3 By additions across the CC bond, alkylidenecyclopropanes can serve as useful precursors of substituted cyclopropanes, 4 which are widely encountered in natural and/or bioactive compounds. 5 Among the different synthetic routes toward alkylidenecyclopropanes, transformations relying on cyclopropenes as precursors are thermodynamically favored owing to the relief of ring strain occurring upon migration of the double bond to the exocyclic position.…”

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confidence: 99%

Synthesis of Functionalized Alkylidenecyclopropanes by Ireland–Claisen Rearrangement of Cyclopropenylcarbinyl Esters

Ernouf

Brayer²,

Folléas³

et al. 2015

Org. Lett.

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Glycolates or glycinates derived from diversely substituted secondary cyclopropenylcarbinols have been involved for the first time in an Ireland-Claisen rearrangement. This reaction allows an efficient and stereoselective access to highly functionalized alkylidenecyclopropanes possessing an α-hydroxy or α-amino acid subunit, which in turn are valuable precursors of substituted cyclopropanes by diastereoselective hydrogenation of the exocyclic alkene.

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“…Noteworthy, methylenecyclopropanes, an appealing building block, may also intercept rhodacyclic intermediates [87]. This C-H activation protocol enables an alternative synthesis of spiro dihydroisoquinolinones and furan-fused azepinones.…”

Section: ð6þmentioning

confidence: 98%

Rh(III)- and Ir(III)-Catalyzed C–C Bond Cross Couplings from C–H Bonds

Wencel‐Delord

Patureau

Glorius

2015

C-H Bond Activation and Catalytic Functionalization I

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(M¼Ir, Rh) is formed and undergoes further transformations, according to the nature of the coupling partner, to finally afford a myriad of valuable, often complex, and otherwise difficult to access scaffolds like heterocycles and polyunsaturated skeletons. The major advances achieved in this field clearly showcase the potential of these catalysts to functionalize latent C-H bonds under surprisingly mild reaction conditions. The aim of this chapter is to present the latest and most representative contributions in the field of Rh(III)-and Ir(III)-catalyzed C-H activation by focusing on the reactivity of the corresponding metallacyclic intermediates.

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Rh(iii)-catalyzed C–H activation/cycloaddition of benzamides and methylenecyclopropanes: divergence in ring formation

Cited by 209 publications

References 101 publications

Mechanistic Understanding of the Divergent Reactivity of Cyclopropenes in Rh(III)-Catalyzed C–H Activation/Cycloaddition Reactions of N-Phenoxyacetamide and N-Pivaloxybenzamide

Mechanistic Understanding of the Divergent Reactivity of Cyclopropenes in Rh(III)-Catalyzed C–H Activation/Cycloaddition Reactions of N-Phenoxyacetamide and N-Pivaloxybenzamide

Synthesis of Functionalized Alkylidenecyclopropanes by Ireland–Claisen Rearrangement of Cyclopropenylcarbinyl Esters

Rh(III)- and Ir(III)-Catalyzed C–C Bond Cross Couplings from C–H Bonds

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