The reactions of fluorenylidene with heteroatomic nucleophiles

Zupancic, Joseph J.; Grasse, Peter B.; Lapin, Stephen C.; Schuster, Gary B.

doi:10.1016/s0040-4020(01)96388-4

Cited by 32 publications

(14 citation statements)

References 35 publications

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“…The deuterium isotope effect on the carbene insertion into OH vs OD, k ec H / k ec D = 1.4 ± 0.2, determined by Laarhoven and co-workers using a 1:1 CH 3 OH/CH 3 OD, is in good agreement with previous measurements for singlet carbene insertion into methanol. − The k ec H / k ec D = 1.7 value determined by Kohler and co-workers by direct transient observation of the 1,1-diphenylmethylcation formed by protonation of singlet diphenylcarbene by methanol is probably the most reliable. It will be used here because, based on the comparison of transient kinetics in the pure CH 3 OH and CH 3 OD solvents instead of in their 1:1 mixture, it is more relevant to our work.…”

Section: Discussionsupporting

confidence: 86%

Photochemistry of the Stilbenes in Methanol. Trapping the Common Phantom Singlet State

Saltiel

Gupta

2018

J. Phys. Chem. A

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A comparative study of the photochemistry of cis- and trans-stilbene in methanol shows that both isomers undergo methanol photoaddition giving similar yields of α-methoxybibenzyl in competition with cis-trans photoisomerization. Methanol addition occurs primarily following torsional relaxation of the lowest excited singlet states of each isomer, c* and t*, to a common twisted singlet excited state intermediate, p*, initially called the phantom singlet state. The addition is consistent with the zwitterionic character of p*. Ether forms by direct 1,2-addition of CHOH to the central carbon atoms and by 1,1-addition following rearrangement to 1-benzyl-1-phenylcarbene. Use of CDOD and GC/MS (gas chromatographic/mass spectroscopic) analysis of the ether products revealed that the ratio of carbene/direct addition pathways is higher starting from cis-stilbene. We conclude that p* formed from c* is hotter than p* formed from t*. Surprisingly, except for favoring the carbene pathway, the use of higher energy photons (254 vs 313 nm) does not affect the overall ether quantum yield starting from cis-stilbene but significantly enhances both pathways starting from trans-stilbene. It appears that carbene formation and direct methanol addition to higher trans-stilbene excited state(s) compete with relaxation to S. Substitution of D for the vinyl Hs of stilbene enhances the direct addition pathway more than 2-fold and strongly suppresses the carbene insertion pathway, revealing a large, k/ k = 6.3, primary deuterium isotope effect in the carbene rearrangement. The 2-fold increase in the ether quantum yield is due primarily to a 2.75-fold increase in the lifetime of p* on deuterium substitution of the vinyl hydrogens.

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Section: Discussionsupporting

confidence: 86%

Photochemistry of the Stilbenes in Methanol. Trapping the Common Phantom Singlet State

Saltiel

Gupta

2018

J. Phys. Chem. A

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“…Similar yields of N-H insertion products have also been observed in studies with diphenylcarbene 21,24 and fluorenylidene. 25 Given the high reactivity of carbenes it is not surprising that a diverse range of functional groups and polymeric linkages are formed in the photopolymerisation of the aminodiazirine 1. The mechanism of formation of these functional groups is complex, but can be accounted for by interpretation of previous chemical and kinetic studies.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of hyperbranched poly(aryl amine)s via a carbene insertion approach

et al. 2008

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A novel diazirine functionalised aniline derivative, 3-(3-aminophenyl)-3-methyldiazirine 1, was prepared and employed as an AB(2)-type monomer in the synthesis of hyperbranched polymers; thus providing the first instance in which polyamines have been prepared via carbene insertion polymerisation. Photolysis of the monomer 1 in bulk and in solution resulted in the formation of hyperbranched poly(aryl amine)s with degrees of polymerisation (DP) varying from 9 to 26 as determined by gel permeation chromatography (GPC). In solution, an increase in the initial monomer concentration was generally found to result in a decrease in the molecular weight characteristics of the resulting poly(aryl amine)s. Subsequent thermal treatment of the poly(aryl amine)s caused a further increase in the DP values up to a maximum of 31. Nuclear magnetic resonance (NMR) spectroscopic analysis revealed that the increase in molecular weight upon thermal treatment resulted from hydroamination of styrenic species formed in the initial photopolymerisation or activation of diazirine moieties.

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“…Knowledge of the kinetics and mechanisms of carbene reactions with various functional groups has advanced over the past 20 years. Laser flash photolysis (LFP) studies performed in several laboratories have played an important role in this field, and rate constants and activation thermodynamic properties have been reported. − These data were obtained by time-resolved absorption spectroscopy, which followed the rate of carbene decay as a function of concentration of various quenchers. Thus, the electronic spectrum of the carbenes is vitally important to correctly identify carbene intermediates and to determine their kinetics.…”

Section: Introductionmentioning

confidence: 99%

Singlet−Triplet Gap, and the Electronic and Vibrational Spectra of Chlorophenylcarbene: A Combined Theoretical and Experimental Study

Pliego¹,

Almeida²,

Celebi³

et al. 1999

J. Phys. Chem. A

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Minimum energy structures of singlet and triplet chlorophenylcarbene, a prototypical carbene, were computed. The singlet-triplet energy separation was predicted to be 7.84 and 7.70 kcal/mol at the UCCSD(T)/6-31+G* and QCISD(T)/6-31+G** levels of theory, respectively, after zero-point correction. This is slightly larger than that predicted by the CAS(6,6) (4.5 kcal/mol), local spin density approximation (5.6 kcal/mol), and the BLYP (7.3 kcal/mol) methods with the 6-31G* basis set reported by Trindle et al. The UV-vis and IR spectra of chlorophenylcarbene were analyzed with the aid of the CASPT2/CASSCF(10,10) and the B3LYP/ 6-31G* levels of theory, respectively. The UV-vis and IR spectra of chlorophenylcarbene were assigned on the basis of these calculations. The ab initio calculations predicted the existence of strong absorption bands in the UV and a weak band in the visible in good agreement with published spectra. The long (750 nm) wavelength band corresponds to electron promotion from the lone pair σ (HOMO) to the π* (LUMO). On the basis of the calculated harmonic frequencies, we cannot assign the 1244 and 1600 cm -1 IR bands observed in an argon matrix to chlorophenyl carbene. The most intense IR band (1225 cm -1 ) corresponds to the symmetric C-C stretch of the carbene and aromatic carbon. The asymmetric and symmetric C-C-Cl stretches are assigned to the bands observed at 847 and 739 cm -1 , respectively.

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The reactions of fluorenylidene with heteroatomic nucleophiles

Cited by 32 publications

References 35 publications

Photochemistry of the Stilbenes in Methanol. Trapping the Common Phantom Singlet State

Photochemistry of the Stilbenes in Methanol. Trapping the Common Phantom Singlet State

Synthesis of hyperbranched poly(aryl amine)s via a carbene insertion approach

Singlet−Triplet Gap, and the Electronic and Vibrational Spectra of Chlorophenylcarbene: A Combined Theoretical and Experimental Study

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