Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)

• Henning Hopf,
• Christian Beck,
• Jean-Pierre Desvergne,
• Henri Bouas-Laurent,
• Peter G. Jones and
• Ludger Ernst

Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20

• recovered by irradiation at 306 nm or by heating. This ‘inverse’ photochromic system has a potential for optical information storage, compound 4 being stable in visible light, at ambient temperature. Keywords: anthracenes; cyclophanes; inverse photochromism; photocycloaddition; Introduction Photochromism

• observed to occur under geometrical constraints [11][12][24] through a triplet state process [25]. [4+2]-Cycloadditions can take place in a hot ground state [26]. This result is reminiscent of the [4+2]-photocycloaddition between two naphthalene substrates for the anti-[2.2](1,4)-naphthalenophane leading

One-pot synthesis of novel 1H-pyrimido[4,5-c][1,2]diazepines and pyrazolo[3,4-d]pyrimidines

• Dipak Prajapati,
• Partha P. Baruah,
• Baikuntha J. Gogoi and
• Jagir S. Sandhu

Beilstein J. Org. Chem. 2006, 2, No. 5, doi:10.1186/1860-5397-2-5

• exploitation of the nucleophilic double bond of uracil is an undeveloped field in view of a great variety of potential products. [9][10][11][12] There have been reports for direct functionalisation of uracil using the C5-C6 double bond via thermolytic[13] and photocycloaddition reactions.[14][15] The