Photochemical cyclodehydrogenation of Lewis acid-conjugates of azobenzenes

Joshua, C. P.; Pillai, V. N. Rajasekharan

doi:10.1016/s0040-4020(01)97509-x

Cited by 14 publications

(8 citation statements)

References 14 publications

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“…1) Table 1 of the primary cyclization product), the theoretical yield is 2/3. The practical yield of 66% of 3 compares favorably to that reported for unsubstituted azobenzene (57%) [7]. We also found that the yield is essentially unaffected by a buttressing effect [1]: starting form 4,4 H -dibromo-3,3 H ,5,5 H -tetramethyl-azobenzene (15), a yield of 64% of benzo[c]cinnoline 13 was obtained.…”

Section: Resultssupporting

confidence: 70%

“…Assuming the mechanism proposed by Joshua [7] in which three molecules azobenzene react to give 2 molecules benzo[c]cinnoline (one molecule of azobenzene is used for the oxidation Table 1. Substituents of compounds 1±15 (cf.…”

Section: Resultsmentioning

confidence: 99%

“…A mechanism for the photocyclodehydrogenation has been proposed in Ref. [7]. In cases where an azobenzene derivative can react to give different products (i.e.…”

Section: Resultsmentioning

confidence: 99%

“…1 and Table 1). The photochemical cyclodehydrogenation of azobenzenes to benzo[c]cinnolines has earlier been investigated by Joshua and Pillai [7,8]. To our knowledge, no reports have been published so far concerning the formation of sterically hindered products via this synthetic pathway.…”

Section: Introductionmentioning

confidence: 99%

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Preparation of 1,10-Dimethyl-benzo[c]cinnolines by Photochemical Cyclodehydrogenation of Azobenzenes

Wimmer

Müller

1998

Monatshefte fuer Chemie

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Photocyclodehydrogenation of methylated azobenzene derivatives to the corresponding benzo[c]cinnolines was utilized for the synthesis of a number of compounds featuring sterically hindered methyl groups with different degrees of sterical hindrance including close mutual methylmethyl interaction. Such compounds are of special theoretical interest in the context of intramolecular dynamics, spectroscopy, and quantum (tunneling) effects. Factors determining synthetic accessibility and product distribution are discussed.

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Section: Resultssupporting

confidence: 70%

Section: Resultsmentioning

confidence: 99%

“…A mechanism for the photocyclodehydrogenation has been proposed in Ref. [7]. In cases where an azobenzene derivative can react to give different products (i.e.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Preparation of 1,10-Dimethyl-benzo[c]cinnolines by Photochemical Cyclodehydrogenation of Azobenzenes

Wimmer

Müller

1998

Monatshefte fuer Chemie

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“…We mention that, under irradiation, azobenzenes could undergo cyclodehydrogenation forming then benzo[c]cinnoline when proton acids [36] or Lewis acids [37,38] are present. In fact a somewhat related compound was reported to Pillai and Purushothaman [39] when photocyclization of azpy was induced.…”

Section: Crystallographymentioning

confidence: 99%

The synthesis, chemical and biological properties of dichlorido(azpy)gold(III) chloride (azpy= 2-(phenylazo)pyridine) and the gold-induced conversion of the azpy ligand to the chloride of the novel tricyclic pyrido[2,1-c][1,2,4]benzotriazin-11-ium cation

Garza-Ortiz

Dulk

Brouwer

et al. 2007

Journal of Inorganic Biochemistry

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The synthesis, chemical and biological properties of dichlorido(azpy)gold(III) chloride (azpy = 2-(phenylazo)pyridine) and the gold-induced conversion of the azpy ligand to the chloride of the novel tricyclic pyrido [2,1-c] AbstractA new Au(III) coordination compound with the ligand 2-(phenylazo)pyridine has been synthesized and fully characterized by means of elemental analysis, IR, UV-visible, conductivity measurements, NMR, electrospray ionization (ESI-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The chemical stability of the cation in this compound, [Au(azpy)Cl 2 ] + (abbreviated: Au-azpy), was analyzed by means of several physicochemical methods. While stable in the solid state, stability studies performed with the gold compound in solution showed an unexpected and unprecedented reactivity. A cationic organic derivative of 2-(phenylazo)pyridine, (abbreviated: pyrium), was produced from the solution and has been isolated as its chloride salt and characterized by crystal structure determination, elemental analysis, NMR, ESI-MS and conductivity studies in solution. This cyclization reaction is reported for the first time in the case of gold coordination compounds.The Au adduct and the pyrium cation were investigated as potential cytotoxic and anticancer agents, and both show moderate to high cytotoxic properties in cisplatin-sensitive and cisplatin-resistant ovarian carcinoma cell lines, A2780; and cisplatin-sensitive and cisplatinresistant murine lymphocytic leukemia cell lines, L1210. Significant anticancer activity against the cisplatin resistant cell lines was found for the pyrium salt, ruling out the occurrence of cross resistance phenomena.

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Photocyclization of Stilbenes and Related Molecules

1984

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On irradiation in solution with ultraviolet (UV) light, cis ‐stilbene undergoes reversible photocyclization to give trans ‐4a,4b‐dihydrophenanthrene, an intermediate that can be trapped oxidatively with hydrogen acceptors such as iodine, oxygen, or tetracyanoethylene to give phenanthrene in high yield. This type of photoreaction occurs with a wide range of substituted stilbenes and related molecules, including various polycyclic and heterocyclic analogs; in addition, certain systems with a single heteroatom (nitrogen, oxygen, or sulfur) in place of the central π bond undergo photocyclization, creating a new five‐membered heterocyclic ring. In some of these photocyclizing systems, the transient dihydroaromatic intermediates are trapped without added oxidants by the elimination of suitable leaving groups or by various hydrogen shifts. Photocyclization is the preferred method for the synthesis of many different polynuclear aromatic systems. The discovery and early development of stilbene photocyclization has been surveyed, and several other general reviews have appeared.

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Photochemical cyclodehydrogenation of Lewis acid-conjugates of azobenzenes

Cited by 14 publications

References 14 publications

Preparation of 1,10-Dimethyl-benzo[c]cinnolines by Photochemical Cyclodehydrogenation of Azobenzenes

Preparation of 1,10-Dimethyl-benzo[c]cinnolines by Photochemical Cyclodehydrogenation of Azobenzenes

The synthesis, chemical and biological properties of dichlorido(azpy)gold(III) chloride (azpy= 2-(phenylazo)pyridine) and the gold-induced conversion of the azpy ligand to the chloride of the novel tricyclic pyrido[2,1-c][1,2,4]benzotriazin-11-ium cation

Photocyclization of Stilbenes and Related Molecules

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