Intramolecular Addition Reactions of Functionalized Arylcarbenes to Arenes.

Guth, Michael; Kirmse, Wolfgang; Mitra, Manjushri; Norin, Torbjörn; Spielbüchler, P.; Pedersen, J. Boiden; Krogsgaard‐Larsen, Povl

doi:10.3891/acta.chem.scand.46-0606

Cited by 12 publications

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“…Although various half-sandwich-type complexes [(η 5 -C 5 H 5 )M(CRR‘)L n ], in particular those with n = 2 and M = Mn or Re, are known, , to the best of our knowledge it has never been observed that they react with either electrophilic or nucleophilic substrates by migratory insertion of the carbene ligand into a C−H bond of the ring. The closest analogy to the formation of C 5 H 4 CHPh 2 from C 5 H 5 and CPh 2 we are aware of goes back to the work of Kirmse et al, which illustrates that arylcarbenes, generated from the corresponding diazo compounds, undergo an intra molecular insertion into the ortho C−H bond of a connected phenyl ring …”

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Two Alternative Routes for the Migratory Insertion of a Carbene Ligand into a C−H Bond

et al. 1998

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It is well-known that transition-metal carbene complexes readily undergo C-C coupling reactions not only with alkenes (olefin metathesis) and alkynes (Dötz reaction) but also with CO and other C-nucleophiles. 1 During attempts to study the reactivity of the halfsandwich-type compounds [(η 5 -C 5 H 5 )Rh(dCPh 2 )(SbiPr 3 )] (1) and the corresponding triisopropylphosphine derivative 2 (Scheme 1), which were prepared from the squareplanar precursors trans-[RhCl(dCPh 2 )L 2 ] and NaC 5 H 5 , 2 we observed that the course of the reaction of 1 and 2 with CO and isocyanides depends critically on the ligand L of the starting material. While the stibane complex 1 on treatment with CO or CNtBu yields the mixed (carbene)(carbonyl) and (carbene)(isocyanide)rhodium compounds [(η 5 -C 5 H 5 )Rh(dCPh 2 )(CX)] (3a, X ) O; 3b, X ) NtBu), the phosphine derivative 2 affords the noncarbene-containing products [(η 5 -C 5 H 5 )Rh(PiPr 3 )(CX)] (4a,b) together with diphenylketene or the corresponding ketenimine. 2, 3 We have now found that PF 3 , despite the similarity of its σ-donor/π-acceptor capabilities with those of CO, reacts with 2 in a completely different way, leading to an unprecedented migratory insertion of the CPh 2 unit into an sp 2 C-H bond.Treatment of compound 2 with PF 3 in benzene at room temperature leads to a smooth change of color from blue to orange and finally to the isolation of the orange air-and moisture-sensitive solid 5 in moderate yield. 4 The most characteristic spectroscopic features of 5 are the signals for the CHPh 2 proton at δ 4.79 in the 1 H NMR and the two resonances for the phosphorus nuclei of the PF 3 and PiPr 3 ligands at δ 119.4 and 79.0 in the 31 P NMR spectrum. 5 Both 31 P NMR signals show strong Rh-P couplings of 446 and 221 Hz, respectively. The X-ray crystal structure analysis of 5 ( Figure 1) 6 X Abstract published in Advance ACS Abstracts, December 15, 1997. (1) (a) Dötz, K. H.; Fischer, H.; Hofmann, P.; Kreissl, F. R.; Schubert, U.; Weiss, K.(4) The preparation of 5 is as follows. A slow stream of PF3 was passed through a solution of 2 (100 mg, 0.20 mmol) in 20 mL of benzene for 20 min at room temperature. After the solution was stirred for another 20 min, the solvent was removed and the oily residue dissolved in 3 mL of pentane. Column chromatography on Al2O3 (neutral, activity grade V) gave upon elution with pentane an orange fraction which was brought to dryness in vacuo. The solid was recrystallized from pentane (-78°C) to afford orange crystals: yield 48 mg (41%).(5) Selected spectroscopic data for 5, 6a, 6b, and 7a (omitting the 1 H and 13 C NMR data for isopropyl and phenyl groups) are as follows. 5: 1 H NMR (200 MHz, C6D6) δ 5.1 (m, 4H, C5H4), 4.8 (m, 1H, CHPh2); 31 P NMR (81.0 MHz, C6D6) δ 119.4 (ddq, 1 J(PF) ) 849.3, 1 J(RhP) ) 446.3, 2 J(PP) ) 77.6 Hz, PF3), 79.0 (dd, 1 J(RhP) ) 221.0, 2 J(PP) ) 77.6 Hz, PiPr3). 6a: 1 H NMR (400 MHz, C6D6) δ 5.72 (d, 3 J(RhH) ) 2.9 Hz, 1H, CHPh2), 5.1, 4.4 (both m, 2H each, C5H4), -12.21 (dd, 1 J(RhH) ) 35.1, 2 J(PH) ) 13.8 Hz, 1H, RhH); ...

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confidence: 85%

Two Alternative Routes for the Migratory Insertion of a Carbene Ligand into a C−H Bond

et al. 1998

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“…In diglyme, benzophenone sensitization gave rise to 17 at the expense of 18 . The triplet-induced transformation, R 2 CN 2 → R 2 CH 2 , does not necessarily involve a carbene intermediate, as was discussed elsewhere . Moreover, 18 was converted into nonvolatile products (polymers?)…”

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Stereochemistry of Carbenic 1,2-Vinyl Shifts

Kirmse

Kopannia

1998

J. Org. Chem.

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Intramolecular reactivity of arylcarbenes: Biphenyl-2-ylcarbenes

Dorra

Gomann

Guth

et al. 1996

J. Phys. Org. Chem.

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Biphenyl-2-ylcarbenes, 2-ArC6H,CR, were generated photolytically and thermally from diazo precursors. Cyclization, leading to fluorenes, competes with capture of the carbenes by methanol but proceeds faster than intramolecular hydrogen shifts (with R = Me) and intermolecular C-H insertion reactions (with R = H in cyclohexane). By comparison of product ratios with kinetic data for related carbenes from the literature, the cyclization rate is estimated as cu 10" s-'. The intramolecular reactivity of biphenyl-2-ylcarbenes is not significantly attenuated by variation of R (R = H, Me, Ph). Very minor effects of triplet sensitization and methanol quenching indicate that fluorenes arise from spin-equilibrated biphenyl-2-ylcarbenes, presumably from the singlet state. When A r = mesityl, the carbene predominantly inserts into C-H bonds of the 2'-methyl groups, giving rise to a dihydrophenanthrene. Formation of a fluorene derivative, by formal insertion into C-C bonds, occurs as a minor process. This unprecedented reaction points to intervention of an o-xylylene in which the methyl group migrates. Laser flash photolysis (LFP) of 2-PhC6H,CN,Ph generates a transient absorption which is due to the To -+ T, transition of 9-phenylfluorene rather than to the presumed o-xylylene. On LFP of 2-ArC,H,CN,Ph in trifluoroethanol-acetonitrile, protonation of the carbenes gives rise to carbocations, 2-ArC,H,CH 'Ph. The transient absorption spectra of these cations are strongly influenced by twisting about the Ar-Ar bond (Ar = P h i o-tolyl< mesityl) whereas the rates of nucleophilic capture vary only slightly. Biphenyl-2-ylcarbenium ions (Ar = R = Ph) cyclize more slowly than the analogous carbenes, by a factor of 310,.

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Intramolecular Addition Reactions of Functionalized Arylcarbenes to Arenes.

Cited by 12 publications

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Two Alternative Routes for the Migratory Insertion of a Carbene Ligand into a C−H Bond

Two Alternative Routes for the Migratory Insertion of a Carbene Ligand into a C−H Bond

Stereochemistry of Carbenic 1,2-Vinyl Shifts

Intramolecular reactivity of arylcarbenes: Biphenyl-2-ylcarbenes

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