Synthesis of oxygen analogs of the penicillins. I. Photocyclization of 2-oxoamides to 3-carbomethoxy-6-hydroxypenams.

Henery-Logan, Kenneth R.; Chen, Chester G.

doi:10.1016/s0040-4039(01)95915-5

Cited by 27 publications

(3 citation statements)

References 6 publications

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“…An example of this is found in studies of photoinduced reactions of α-ketoamides 1 that produce β-lactams 5 (Scheme ). Following a number of earlier studies, − Aoyama and co-workers − conducted a series of exploratory investigations that focused on the scope and mechanism of this process. This group proposed that this reaction is initiated by hydrogen atom abstraction by the carbonyl oxygen of the excited ketone from an amide α-carbon.…”

Section: Introductionmentioning

confidence: 99%

β-Lactam-Forming Photochemical Reactions of N-Trimethylsilylmethyl- and N-Tributylstannylmethyl-Substituted α-Ketoamides

et al. 2004

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Two mechanisms have been proposed for the beta-lactam-forming photochemical reactions of alpha-ketoamides. One, suggested by Aoyama, involves excited-state H-atom abstraction while the other, put forth by Whitten, follows a sequential SET-proton-transfer route. The photochemical properties of N-trimethylsilylmethyl- and N-tributylstannylmethyl-substituted alpha-ketoamides were explored in order to gain information about the mechanism of this process and to develop a regioselective method for beta-lactam formation. The results of this effort show that (1) photoreactions of N-trimethylsilylmethyl-substituted alpha-ketoamides proceed by competitive H-atom abstraction and sequential SET-desilylation pathways and (2) a sequential SET-destannylation pathway is preferentially followed in photochemical reactions of the tributylstannylmethyl-substituted alpha-ketoamides.

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Section: Introductionmentioning

confidence: 99%

β-Lactam-Forming Photochemical Reactions of N-Trimethylsilylmethyl- and N-Tributylstannylmethyl-Substituted α-Ketoamides

et al. 2004

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“…Photochemical intramolecular H abstractions in carbonyl compounds have found several synthetic applications [1][2][3][4][5][6][7][8][9][10][11] including the synthesis of numerous exotic carbocyclic and heterocyclic scaffolds that are otherwise very difficult to obtain under thermal conditions. The exceptional behaviour of the propargyl 1,4-biradical in forming photoproducts via unsaturated carbenes 12,13 has been investigated by Agosta and Margaretha, 14 and has encouraged us to study the photochemistry of chromenones containing the propargyl group.…”

Section: Introductionmentioning

confidence: 99%

Phototransformation of 3-alkoxychromenones: regioselective photocyclisation and dealkoxylation

Khanna

Dalal

Kumar

et al. 2015

Photochem Photobiol Sci

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The phototransformation of some 2-(3-methoxyphenyl)-4H-chromen-4-ones bearing a propynyloxy moiety at the 3-position has been described. On photolysis with pyrex-filtered UV light from a Hg lamp (125 W), these chromenones produced a major amount of 5-ethynyl-2-methoxy-6-oxa-benzo[5,6-c]xanthen-7-ones consisting of an exotic tetracyclic scaffold. These photoproducts have been envisioned to be produced through regioselective ring closure at the 6'-position of the 2-(3'-methoxy)phenyl moiety of the initially formed 1,4-biradical via a γ-H abstraction mechanism. No product whatsoever was observed through ring closure at the 2'-position. This behaviour has been found to be in accordance with the directive influence observed in free radical aromatic substitutions. This regioselective photocyclisation is further supported by calculations made from 3D structures (MM2 program). In addition, during the irradiation of these substrates, 2-(3-methoxyphenyl)-4H-chromen-4-ones were also realised through dealkoxylation. The structures of the substrates and photoproduct(s) have been determined by their spectroscopic (IR, NMR, mass spectrometry) studies.

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“…Photochemical H-abstraction in the carbonyl substrates has been proved an exciting synthetic tool for the generation of numerous exotic carbocyclic and heterocyclic compounds [1][2][3][4][5][6][7][8][9][10][11]. 3-Alkoxy-2-arylchromones [12][13][14][15][16] undergo intramolecular photo-H-abstraction to provide the tetracyclic products.…”

Section: Introductionmentioning

confidence: 99%

Photocyclisations of some 3‐alkoxy‐2‐thienylchromones

Yusuf

Kumar

Gupta

2008

Journal of Heterocyclic Chem

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Synthesis of oxygen analogs of the penicillins. I. Photocyclization of 2-oxoamides to 3-carbomethoxy-6-hydroxypenams.

Cited by 27 publications

References 6 publications

β-Lactam-Forming Photochemical Reactions of N-Trimethylsilylmethyl- and N-Tributylstannylmethyl-Substituted α-Ketoamides

β-Lactam-Forming Photochemical Reactions of N-Trimethylsilylmethyl- and N-Tributylstannylmethyl-Substituted α-Ketoamides

Phototransformation of 3-alkoxychromenones: regioselective photocyclisation and dealkoxylation

Photocyclisations of some 3‐alkoxy‐2‐thienylchromones

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