Generation of 1,2-Bisketenes from Cyclobutene-1,2-diones by Flash Photolysis and Ring Closure Kinetics J. Am. Chem. Soc. 1997, 119, 12125−12130

Allen, Annette D.; Colomvakos, Jim D.; Diederich, F.; Egle, Ian; Hao, Xinyu; Li, R.; Lusztyk, J.; Ma, Jingwen; McAllister, Michael A.; Rubin, Yves; Sung, Kung-Bin; Tidwell, T. T.; Wagner, Brian D.

doi:10.1021/ja9855141

Cited by 4 publications

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“…498 Ring closure of bisketene 687 to 260 is calculated to be strongly exothermic. 499 Trapping of bisketene by electron-deficient dienophiles such as maleic anhydride gives the cycloaddition product 688 (Scheme 159). 497 Bisketenes, generated thermally or photochemically from benzocyclobutenediones, can be trapped by dienophiles.…”

Section: Reactions Of Benzocyclobutenedionementioning

confidence: 99%

Cyclobutarenes and Related Compounds

2003

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A general method for the synthesis of cyclobutarenes involves 1,4-elimination from adjacent benzylic positions, followed by ring closure of the resulting o-quinodimethane. The earliest report in which an o-quinodimethane was implicated was the reaction of R,R,R′,R′-tetrabromo-o-xylene (4) with iodide to give the 1,2-dibromocyclobutarene 6, via o-quinodimethane 5. Treatment of 6 with NaI in acetone gave diiodide 7, which on catalytic reduction gave 1 (Scheme 1). [15][16][17] Cava and co-workers confirmed that 5 was an intermediate by trapping experiments using sev-eral dienophiles. 18 A similar procedure has been used to prepare 1,2-diphenylcyclobutarene. 19 Heterocyclic analogues may also be prepared by the 1,4-elimination of halogen from suitable precursors. Compounds 9 and 11 have been synthesized from 8 and 10, respectively, as illustrated in Scheme 2. 20 A variation of the method involves the conversion of R-alkyl-R-bromosulfones into cyclobutarenes using tetrabutylammonium fluoride (TBAF) in acetonitrile at 20-25 °C to effect the elimination. 21 The desired cyclobutarene is often accompanied by olefinic side products, as illustrated in the preparation of cyclobutarene 13, which is accompanied by 14 (eq 1) (Table 1). Anil K. Sadana was born in Panipat, India. He did his M.Sc (1990) and M. Phil (1992) from Kurukshetra University, India. He obtained his Ph.D. degree in 1999 under the guidance of Prof. Om Prakash. His Ph.D. work focused on the utility of hypervalentiodine reagents in the synthesis of heterocyclic compounds. He then joined Prof. W. E. Billups lab as postdoctoral research associate in 2000. He is presently working on small ring compounds and carbon nanotubes. Rajesh Kumar Saini was born in 1966 in Ambala, India. He received his masters degree in 1989 and his Ph.D. in 1996 from Kurukshetra University, India. After his doctorate he moved to the United States for his postdoctoral studies. After a brief stay at Sam Houston State University he joined Rice University, where he is working as a Research Scientist in the laboratories of Prof. W. E. Billups and Prof. Richard E. Smalley. His research has concentrated on small ring compound and the development of carbon nanotube chemistry. W. E. Billups was born in 1939 in Huntington, West Virginia. He received his B.S. in Chemistry Degree from Marshall University in 1961. This was followed by a period in industry after which he entered the graduate school of the Pennsylvania State University in 1968 and received the Ph.D. in 1970. He then joined the chemistry department at Rice University. He served as the Department Chair from July 1985 until December 1991. His research interests are divided among the areas of small-ring compounds, reactive intermediates, chemistry of free metal atoms and more recently fullerene and carbon nanotube chemistry.

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Section: Reactions Of Benzocyclobutenedionementioning

confidence: 99%

Cyclobutarenes and Related Compounds

2003

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“…11 The IR spectroscopy of ketenes has been extensively studied in cryogenic matrices [12][13][14] and has been applied recently to investigate ketene reactions toward nucleophiles in this medium. 15,16 We [17][18][19][20][21] and others 22 detection (LFP-TRIR) is ideally suited for both mechanistic and kinetic studies of ketenes in solution since the characteristic spectroscopic region near 2100 cm -1 is transparent to most solvents and void of absorptions due to other photogenerated transients and products. In this paper, we employ LFP-TRIR for systematic studies of the infrared spectroscopic properties of ketenes and explore the mechanism and kinetics of the ketene amine reactions.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopy and Absolute Reactivity of Ketenes in Acetonitrile Studied by Laser Flash Photolysis with Time-Resolved Infrared Detection

et al. 1998

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Laser flash photolysis with time-resolved infrared detection of transients (LFP-TRIR) has been used to study the IR spectroscopy and reactivity of a number of substituted ketenes, prepared by the 308-nm photolysis of α-diazocarbonyl precursors in acetonitrile solution at room temperature. The correlation of the experimental ketene asymmetric stretching frequency to the Swain−Lupton field (F) and resonance (R) effect substituent parameters was unsatisfactory, whereas the correlation to the inductive substituent parameter (σI) of Charton gave excellent results. This suggests that the asymmetric stretching frequency of substituted ketenes depends mainly on the inductive (i.e., field) effect of the substituents. The mechanism and kinetics of the reactions of these ketenes with various amines in acetonitrile were also studied. An intermediate species identified as either zwitterionic ylide or amide enol formed in the nucleophilic addition of the secondary amine to the Cα of the ketene is observed by TRIR. The decay of this species is assisted by the amine and is concomitant with the formation of an amide, the final product of the reaction. Our kinetic data on ketene amine reactions show a general trend, indicating a much higher reactivity (ca. 3 orders of magnitude difference in the corresponding rate constants) of secondary amines compared with that of tertiary amines. Secondary diethylamine shows reactivity similar to those observed for primary amines, while secondary piperidine seems to be, in general, somewhat more reactive. The observed trend is rationalized in terms of the steric effects exerted by both amine and ketene substituents. Our data on para-substituted phenyl ketenes provide support for the negative charge development on the ketene moiety in the transition state, with electron-withdrawing substituents accelerating and electron-releasing substituents slowing down the addition reaction.

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“…DCP is produced together with CO, and results from decarbonylation of the bisketene, probably involving intermediacy of the ketenylcarbene. 23 The DFT(B3LYP)/6-311++G(d,p) calculations indicated that the trans-trans conformer of DCP should be more stable than the cis-trans form by 3.42 kJ mol -1 (3.59 kJ mol -1 , if zeropoint vibrational energy correction is considered). The spectroscopic data indicate that, at the end of the UV-irradiation, the two conformers are present in the matrix in a proportion that is equal to the degeneracy of the conformational level (1 for the trans-trans conformer and 2 for the cis-trans form).…”

Section: Irradiation Of the Matrixes (Photochemistry Experiments)mentioning

confidence: 99%

“…[16][17][18][19][20][21][22][23] Observation of deltic acid (C 3 O 3 H 2 ; 2,3dihydroxycycloprop-2-en-1-one) as a photoproduct generated from squaric acid was also reported. 22,23 Maier and Rohr 22 noticed that the deltic acid, produced by irradiation of the matrixisolated squaric acid, gives rise to at least two bands owing to OH stretching vibrations (νOH), whereas the trans-trans conformer of this compound should give rise to only one infrared-active νOH band. Nevertheless, the experimental results were interpreted assuming the presence of only the trans-trans conformer.…”

Section: Introductionmentioning

confidence: 99%

“…15 Since that time, this reaction has been used to generate 1,2-bisketenes, but usually these species have only been observed at low temperature, often in matrixes, because of their facile thermal ring closure. [16][17][18][19][20][21][22][23] Observation of deltic acid (C 3 O 3 H 2 ; 2,3dihydroxycycloprop-2-en-1-one) as a photoproduct generated from squaric acid was also reported. 22,23 Maier and Rohr 22 noticed that the deltic acid, produced by irradiation of the matrixisolated squaric acid, gives rise to at least two bands owing to OH stretching vibrations (νOH), whereas the trans-trans conformer of this compound should give rise to only one infrared-active νOH band.…”

Section: Introductionmentioning

confidence: 99%

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Molecular Structure, Infrared Spectrum, and Photochemistry of Squaric Acid Dimethyl Ester in Solid Argon

et al. 2006

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Squaric acid dimethyl ester (C(6)O(4)H(6); 3,4-dimethoxycyclobut-3-ene-1,2-dione; DCD) was studied by matrix isolation infrared spectroscopy and by density functional theory (B3LYP) and ab initio (MP2) calculations with the 6-31++G(d,p) and 6-311++G(d,p) basis sets. Three conformers of the compound were theoretically predicted. The two most stable conformers were identified in low-temperature argon matrixes and the energy gap between them was determined. The trans-trans conformer (C(2)(v)) was found to be more stable than the cis-trans form (C(s)) by 4.2 kJ mol(-1), in consonance with the theoretical predictions (MP2 calcd = 3.9 kJ mol(-1)). In situ broadband UV irradiation (lambda > 337 nm) of the matrix-isolated compound was found to induce the ring-opening reaction leading to production of the bisketene, 2,3-dimethoxybuta-1,3-diene-1,4-dione as well as the trans-trans --> cis-trans conformational isomerization. The latter phototransformation allowed separation of the infrared spectra of the two conformers initially trapped into a low-temperature matrix. Upon higher energy irradiation (lambda > 235 nm), the main observed photoproducts were CO and deltic acid dimethyl ester (C(5)O(3)H(6); 2,3-dimethoxycycloprop-2-en-1-one), the latter being obtained in two different conformations (trans-trans and cis-trans). According to the experimental data, deltic acid dimethyl ester is produced by decarbonylation of the initially formed bisketene and not by direct CO extrusion from DCD.

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Generation of 1,2-Bisketenes from Cyclobutene-1,2-diones by Flash Photolysis and Ring Closure Kinetics J. Am. Chem. Soc. 1997, 119, 12125−12130

Cited by 4 publications

References 0 publications

Cyclobutarenes and Related Compounds

Cyclobutarenes and Related Compounds

Spectroscopy and Absolute Reactivity of Ketenes in Acetonitrile Studied by Laser Flash Photolysis with Time-Resolved Infrared Detection

Molecular Structure, Infrared Spectrum, and Photochemistry of Squaric Acid Dimethyl Ester in Solid Argon

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