Photochemical transformations of small ring carbonyl compounds. XIX. Photochemistry of benzoylcyclobutanes

Padwa, Albert; Alexander, Edward C.; Niemcyzk, Mark

doi:10.1021/ja01030a042

Cited by 33 publications

(15 citation statements)

References 11 publications

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“…They suggest that the excitation energy originally absorbed by the carbonyl group in the (*←n) transition is delocalized into the cyclopropyl rings, efficiently reducing the Norrish type I cleavage. Padwa et al use the same argument 57,58 to describe a similar decrease in the Norrish type I cleavage observed in phenyl containing ketones.…”

Section: B Previous Studies Of Cyclopropyl Containing Ketonesmentioning

confidence: 85%

Photodissociation dynamics of dicyclopropyl ketone at 193 nm: Isomerization of the cyclopropyl ligand

Clegg

Parsons

Klippenstein

et al. 2003

The Journal of Chemical Physics

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The photodissociation dynamics of dicyclopropyl ketone are investigated using time-resolved Fourier transform infrared spectroscopy and photofragment ion imaging spectroscopy. The photodissociation products are C3H5+CO+C3H5, and the isomerization dynamics of C3H5 are the focus of this paper. Electronic structure calculations are used to define the potential energy surface, while a two-step phase space theory model predicts excitation in the CO product. The vibrational energy distribution of the CO product is not described by this statistical distribution, and is more excited than that observed in the analogous dissociation of acetone. The translational energy distribution of CO indicates an exit barrier on the potential energy surface. Contrary to expectations based on the photodissociation of other aliphatic ketones, the hydrocarbon products are not cyclopropyl radicals. Instead, the excited dicyclopropyl ketone undergoes a ring-opening isomerization to form diallyl ketone, followed by dissociation producing allyl radicals and carbon monoxide. Some of the allyl radicals have sufficient internal energy to decompose to allene+H.

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Section: B Previous Studies Of Cyclopropyl Containing Ketonesmentioning

confidence: 85%

Photodissociation dynamics of dicyclopropyl ketone at 193 nm: Isomerization of the cyclopropyl ligand

Clegg

Parsons

Klippenstein

et al. 2003

The Journal of Chemical Physics

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“…ketone, the sum is about 0.6012 at 120°and ca. 20 Torr. For I, the sum of the quantum yields is about 0.17 under similar conditions.…”

Section: Discussionmentioning

confidence: 99%

Photolysis of cyclopropyl ketones in the vapor phase and in solution

Pitts¹,

Marsh²,

Schaffner³

et al. 1971

J. Am. Chem. Soc.

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The vapor-phase (at 120°) and solution photochemistry of dicyclopropyl ketone (I), methyl 2,2-dimethylcyclopropyl ketone (II), cyclopropyl 2,2-dimethylcyclopropyl ketone (III), propyl cyclopropyl ketone (IV), 3butenyl cyclopropyl ketone (V; in the vapor phase), and 3-methyl-3-butenyl cyclopropyl ketone (VI; in solution) has been investigated. Dicyclopropyl ketone (I), when irradiated in the vapor phase in its -* * band at 2537-2654 A, yields cyclopropyl c/j-propenyl ketone, cyclopropyl irans-propenyl ketone, allyl cyclopropyl ketone, and carbon monoxide as major products with quantum yields of 0.125, 0.025, 0.01, and 0.01, respectively. These quantum yields are temperature and pressure independent. Carbon monoxide is formed via a Norrish type I elimination, whereas the photoisomers result from a ir*-assisted cyclopropane fission reaction. On irradiation of ketone I at 2537 and at 3130 Á in isooctane and benzene solutions, no photochemical reaction is observed. In isopropyl alcohol, however, irradiation leads to reductive cleavage of one ring to yield propyl cyclopropyl ketone (IV). The reaction is presumably due to hydrogen abstraction from the solvent by the excited carbonyl in the primary photochemical process. Ketones II and III, when photolyzed in their ntr* bands at 2537-2654 Á in the vapor phase and at 2537 or 3130 A in isooctane, benzene, or ethanol solutions, undergo Norrish type II processes to yield 5-methyl-5-hexen-2-one (VII) and 3-methyl-3-butenyl cyclopropyl ketone (VI), respectively. The quantum yields in the vapor phase are 0.30 and 0.25, respectively, and they are independent of pressure. On the basis of experiments with nitric oxide and 2,3-dimethyl-2-butene in the vapor phase, the Norrish type II process for ketones II and III presumably proceeds through their first excited singlet state. Infrared spectroscopy evidence for an enol intermediate as the primary photoproduct of II in the vapor phase is presented. Ketones IV and V proved to be quite stable to irradiation in the vapor phase at 2537-2654 A. Similar photostabilities were observed for ketone IV in isopropyl alcohol and for ketone VI in ethanol solution using 3130-Á light.

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“…[29] Compound 14 b has also been accessed in low yield through reduction of the corresponding ketone (see Section 3.2). The2 -substituted phenyl analogue (16 a)i sm ore accessible, [33] representing the major product of the photolysis of cyclobutyl phenyl ketone via (thermally reversible) [33a,b] Norrish-Yang (NY) [34] cyclisation (Scheme 2B). TheNYcyclisation strategy is compatible with electron-poor and electron-neutral substrates (16 b-f), but is less tolerant of electron-rich systems such as vinyl and 2-furyl cyclobutyl ketones.…”

Section: Reactive Intermediates On Bcp Bridge Positionsmentioning

confidence: 99%

Bridge Functionalisation of Bicyclo[1.1.1]pentane Derivatives

et al. 2021

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Escaping from flatland", by increasing the saturation level and three-dimensionality of drug-like compounds, can enhance their potency, selectivity and pharmacokinetic profile. One approach that has attracted considerable recent attention is the bioisosteric replacement of aromatic rings, internal alkynes and tert-butyl groups with bicyclo[1.1.1]pentane (BCP) units. While functionalisation of the tertiary bridgehead positions of BCP derivatives is well-documented, functionalisation of the three concyclic secondary bridge positions remains an emerging field. The unique properties of the BCP core present considerable synthetic challenges to the development of such transformations. However, the bridge positions provide novel vectors for drug discovery and applications in materials science, providing entry to novel chemical and intellectual property space. This review aims to consolidate the major advances in the field, serving as a useful reference to guide further work that is expected in the coming years. Joseph Anderson completed his MChem in 2020 (University of Oxford, Prof. Timothy Donohoe) working on cobalt-catalysed transformations of boronic acids. He subsequently joined the GSK/University of Strathclyde Collaborative Industrial PhD Programme, where he is currently working under the supervision of Dr Darren Poole, Dr Nicholas Measom and Prof. John Murphy on bicyclo[1.1.1]pentane methodology. Nicholas Measom completed his PhD in 2017 (GSK/University of Strathclyde Collaborative Industrial PhD programme, Dr David Hirst and Dr Craig Jamieson) working on the synthesis and application of bicyclo[1.1.1]pentanes within Lp-PLA2 inhibitors. He joined GSK as a synthetic medicinal chemist in 2017 and became an Investigator in 2020. Darren Poole completed his DPhil in 2014 (University of Oxford, Prof. Timothy Donohoe) where he worked on nucleophilic dearomatisation reactions, and hydrogen borrowing reactions of methanol. He joined GSK's Flexible Discovery Unit as a synthetic chemist in 2014, and is now a Scientific Leader and GSK Fellow in the Medicinal Chemistry department. His research interests are particularly focussed on the application of new synthetic methodologies and technologies in drug discovery. John Murphy was born in Dublin and educated at the University of Dublin (TCD) and the University of Cambridge. After Fellowships at Alberta and Oxford, he was appointed as Lecturer, then Reader, at the University of Nottingham. Since 1995, he has held the Merck-Pauson Professorship at the University of Strathclyde. His interests are in mechanism and synthesis.

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Photochemical transformations of small ring carbonyl compounds. XIX. Photochemistry of benzoylcyclobutanes

Cited by 33 publications

References 11 publications

Photodissociation dynamics of dicyclopropyl ketone at 193 nm: Isomerization of the cyclopropyl ligand

Photodissociation dynamics of dicyclopropyl ketone at 193 nm: Isomerization of the cyclopropyl ligand

Photolysis of cyclopropyl ketones in the vapor phase and in solution

Bridge Functionalisation of Bicyclo[1.1.1]pentane Derivatives

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