Photochemical transformations of small ring carbonyl compounds. 68. Photochemical rearrangement in the 2(5H)-furanone system

Padwa, Albert; Dehm, David

doi:10.1021/ja00849a063

Cited by 8 publications

(3 citation statements)

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“…Vinyl(3,5-dimethyl-4-isoxazolyl)carbinol (12). A solution of 15.43 g (0.123 mol) of aldehyde17 13 in 180 mL of dry ether was cooled in an ice bath and treated with 240 mL of a solution of vinylmagnesium bromide in tetrahydrofuran (1.0 , 0.24 mol) under a nitrogen atmosphere.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and photochemistry of heterocyclic norbornenyl ketones

Sauers¹,

Hagedorn²,

Arnum³

et al. 1987

J. Org. Chem.

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Section: Methodsmentioning

confidence: 99%

Synthesis and photochemistry of heterocyclic norbornenyl ketones

Sauers¹,

Hagedorn²,

Arnum³

et al. 1987

J. Org. Chem.

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“…Irradiation of 3,5-Diphenyl-2(5//)-furanone (1) in the Presence of Excess 1,1 -Dimethoxyethylene. A solution containing 100 mg of 1 in 475 mL of dry benzene containing 1.0 g of 1,1 -dimethoxyethylene was irradiated with a 450-W Hanovia lamp equipped with a Corex filter for 1 h. Removal of the solvent left a crystalline solid which was recrystallized from benzene-ligroin to give the [2 + 2] cycloadduct 11 (125 mg) in 91% yield: mp 181-182 °C; IR (KBr) 1760cm-1; NMR (CDCI3, 100 MHz) 2.30 (dd, 1 , / = 12.0 and 1.5 Hz), 2.50 (d, 1 H,y = 12.0 Hz), 2.78 was added a solution containing 1.35 g of bromine in 5 mLof carbon disulfide. After stirring for 1 h, the reaction mixture was quenched by the addition of 20 mL of a 1% aqueous sodium thiosulfate solution.…”

Section: Experimental Section59mentioning

confidence: 99%

Photochemical transformations of small ring carbonyl compounds. 101. Migratory aptitude studies in the photochemical rearrangement of 2(5H)-furanones

Padwa¹,

Brookhart²,

Dehm³

et al. 1978

J. Am. Chem. Soc.

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Irradiation of 3,5-diphenyl-S-aryl-2(5H)-furanones in benzene results in a novel rearrangement and affords a mixture of 3,4-diphenyI-S-aryl-and 3,S-diphenyl-4-aryl-2( 5H)-furanones. Phosphorescence, sensitization, and quenching studies confirm the involvement of a T-T* triplet state in these reactions. The rate constants of aryl group migration were determined from quenching studies using piperylene as a quencher. These were found to be 0.18 X lolo, 1.3 X 1O'O. and 0.9 X 10'O s-' for migration of phenyl, p-anisyl, and p-cyanophenyl. respectively. Thus, p-An and p -C N P h are more reactive migrating groups than phenyl by factors of 7.2 and 5.0 in benzene. The preferential migration ofp-anisyl over phenyl (16/ 1) and p-cyanophenyl ovcr phenyl (3.5/ I ) suggests that the excited state involved in benzene has significant odd-electron character on the :j carbon of the tuJ-unsaturated lactone moiety. A striking feature of these rearrangements is that a substantial crobsover in migratory aptitude occurs upon changing the solvent from ben7ene to inethanol. A iionniigratingp-anisyl group W;IS found to significant-I! accelerate the rate of phenyl migration in methanol. Whereas the migration ofp-anisyl in preference to phenxl in benzene is attributable to stabilimtion of the radical like free valence by the migrating group, the slight preference for migration of phenyl over p-anisyl in methanol may be attributed to stabilization of the electron deficicncy which develops at C5 by the nonmigrating p-anisql group. The above results serve to emphasize the important role that electron distribution plays in photochemical migratory processcs Light-induced transformations of five-membered enol lactones have been the subject of recent intensive These compounds undergo a facile decarbonylation when subjected to ultraviolet excitation and produce a,@unsaturated ketones as primary photoproducts. Chapman and McIntosh have previously noted that a critical requirement for clean photochemical cleavage of the acyl-oxygen bond is the presence of a double bond adjacent to the ether ~x y g e n .~ Stabilization of the incipient oxy radical was considered to be a determining factor in the photocleavage of this bond. In sharp contrast to the extensive studies concerned with the photochemistry of enol lactones. only scattered reports have appeared concerning the photochemical behavior of the related a,P-unsaturated y-lactone As part of a continuing program dealing with the photochemical transformations of unsaturated lactones,I0 we found that 5,5-diaryl-2( 5H)-furanones undergo aryl group migration when subjected to ultraviolet excitation." During the course of our studies with this system, we uncovered a striking crossover in the competitive migratory aptitudes of aryl groups which arises from a solvent alteration.12 As there are relatively few examples of excited state migratory aptitudes being controlled by solvent variation,I3 we decided to examine the photochemistry of this system in greater detail. We report here the results of this study w...

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“…In the past the study of the substituent effect on the photochemical reaction of ketones has provided much information concerning the electronic nature of species undergoing rearrangement.3 Such an approach was found to be useful in interpreting photochemistry of the di-ir-methane4 and sigmatropic rearrangements5 and of lactones. 6 In a hope that such a study would prove to be similarly informative in understanding the photorearrangement of 4-pyrones7 and 4-pyridones,8 we have examined the effect of para substituents on selectivity in the photoisomerization of 2,6-dimethyl-3-phenyl-5-(para-substituted phenyl)-4-pyrones and 1,2,6-trimethyl-3-phenyl-5-(para-substituted phenyl)-4-pyridones to the 2-pyrones and 2-pyridones, respectively. In the preceding paper9 the quenching effect by dienes and the external heavy-atom effect on quantum yield indicated that the ir,ir* singlet state was responsible for the photorearrangement of 4-pyrones to 2-pyrones and that of 4-pyridones to 2-pyridones.…”

mentioning

confidence: 99%