Allene oxide-cyclopropanone isomerization. Low barrier pathway on the CNDO [complete neglect of differential overlap]/2 energy surface

Zandler, Melvin E.; Choc, Charles E.; Johnson, Carolyn K.

doi:10.1021/ja00817a052

Cited by 26 publications

(6 citation statements)

References 1 publication

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“…Oxyallyl ( 1 ) has long been considered as a potential intermediate or transition structure in the rearrangement of allene oxide ( 2 ) to cyclopropanone ( 3 ) − and in the ring opening and closing reactions of substituted cyclopropanones that result in racemization and isomerization. − Early experimental evidence for the existence of allene oxide as a viable species was based on the characterization of its reaction products, since its apparent high reactivity precluded its isolation. However, in 1968 Camp and Greene reported that the epoxidation of 1,3-di- tert -butylallene gave the first isolable allene oxide, 1,3-di- tert -butylallene oxide, which when heated to 100 °C underwent rearrangement to trans -2,3-di- tert -butylcyclopropanone.…”

Section: Introductionmentioning

confidence: 99%

Rearrangements of Allene Oxide, Oxyallyl, and Cyclopropanone

1998

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A detailed theoretical study of the rearrangement of allene oxide to cyclopropanone and the racemization of substituted cyclopropanones and the isomerization of substituted cyclopropanones is presented. The rearrangement of allene oxide to cyclopropanone was found to proceed in a stepwise fashion in which allene oxide first undergoes conversion to oxyallyl via a newly found transition structure with subsequent ring closure of the oxyallyl to cyclopropanone. It is shown that a previously found transition structure is on the pathway that results in the racemization of chiral-substituted cyclopropanones. A new transition structure was also located that accounts for the previously observed conversion of cis-2,3-di-tert-butylcyclopropanone to its trans diastereomer. The discussion is based on the results of DFT and CASSCF methods. IRC calculations were carried out for all transition structures located. Single-point energies were calculated with the CASPT2N, QCISD(T), and UQCISD(T) methods. Good agreement was found between the calculated results and those available from experiment.

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Section: Introductionmentioning

confidence: 99%

Rearrangements of Allene Oxide, Oxyallyl, and Cyclopropanone

1998

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“…(ii) 9-Ethyl-9-(2,2,2-trifluoroethoxy)fluorene (5b) (2%) d H (500 MHz; CDCl 3 ) 7.30-7.82 (m, 8H), 3.60 (2H, q, J9.0), 2.37 (3H, q, J7.5), 0.92 (3H, t, J7.5); GC-MS (m/z): 263 (100), 193 (5), 180 (55), 152 (30), 57 (30).…”

Section: Photolysis General Proceduresmentioning

confidence: 99%

“…(iv) 1-(9-Fluorenyl)-1-propanone 34 (7b) (28%) d H (500 MHz; CDCl 3 ) 7.30-7.84 (8H, m), 5.05 (1H, s), 3.56 (2H, q, J7.5), 0.96 (3H, t, J7.5); GC-MS (m/z): 222 (15), 207 (3), 165 (65), 139 (10), 57 (100). (ii) 9-Pentyl-9-(2,2,2-trifluoroethoxy)fluorene (5c) (40%) GC-MS (m/z): 334 (5), 263 (100), 180 (30), 178 (25) 152 (15).…”

Section: Photolysis General Proceduresmentioning

confidence: 99%

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Effect of steric bulk on the absolute reactivity of allene oxides

Konecny

Schepp

2009

Org. Biomol. Chem.

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Alpha-alkyl substituted fluorenylidene allene oxides were generated photochemically from appropriately substituted fluorenol derivatives in 2,2,2-trifluoroethanol (TFE) in order to assess the affect of steric bulk on the absolute reactivity of the allene oxides. The absolute reactivities of the allene oxides were measured using nanosecond laser flash photolysis, and were found to change little in TFE upon going from alpha-methyl to alpha-butyl to alpha-t-butyl. However, all three alpha-alkyl substituted allene oxides were considerably more reactive than the alpha-hydrogen derivative, indicating that steric bulk did not result in a decrease in reactivity as is typically found in other allene oxides. The contrary reactivity of the fluorenylidene allene oxides is explained by examining in detail the reactions of these allene oxides, determined from product studies.

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“…lower energy path for the rearrangement. 4 In two cases, the aliene oxides themselves have been isolated.5 For example, the monoepoxide of 1,3-di-fert-butylallene can be isolated, and it rearranges cleanly to 2,3-di-ferf-butylcyclopropanone with a half-life of ca. 5 h at 100 °C.…”

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confidence: 99%

Formation and cyclization of allenic phosphonic acids. 7. Epoxidation of allenic phosphonic acids. Intramolecular trapping of allene oxides

Macomber¹

1978

J. Org. Chem.

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Allene oxide-cyclopropanone isomerization. Low barrier pathway on the CNDO [complete neglect of differential overlap]/2 energy surface

Cited by 26 publications

References 1 publication

Rearrangements of Allene Oxide, Oxyallyl, and Cyclopropanone

Rearrangements of Allene Oxide, Oxyallyl, and Cyclopropanone

Effect of steric bulk on the absolute reactivity of allene oxides

Formation and cyclization of allenic phosphonic acids. 7. Epoxidation of allenic phosphonic acids. Intramolecular trapping of allene oxides

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