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

• for MCH solution in Figure 9. One observes a drop of 50% absorbance after 8 cycles for MCH and 5 cycles for CH3CN (not shown). The photolysis at 306 nm must involve one or several photoreactions leading to products transparent at 392 nm. Thermal dissociation (a retro Diels-Alder reaction, see below

Diastereoselective and enantioselective reduction of tetralin- 1,4-dione

• E. Peter Kündig and
• Alvaro Enriquez-Garcia

Beilstein J. Org. Chem. 2008, 4, No. 37, doi:10.3762/bjoc.4.37

• % conversion) [6], and by photolysis of the Dewar benzene 5 at low temperature in a solid matrix [7] (Scheme 2). While dione 2 is readily synthesized, it remains a chemically unexplored curiosity. This simple molecule, and its π-metal complexes, drew our attention and interest for their potential in synthesis

Synthesis of spiropyrans: H-abstractions in 3-cycloalkenyloxybenzopyrans

• Satish C. Gupta,
• Mandeep Thakur,
• Somesh Sharma,
• Urmila Berar,
• Surinder Berar and
• Ramesh C. Kamboj

Beilstein J. Org. Chem. 2007, 3, No. 14, doi:10.1186/1860-5397-3-14

• cleavage. Synthesis of 3-Cycloalkenyloxybenzopyrans. Photolysis of 6-chloro-3-(1"-cyclohept-2"-enyloxy)-2-(2'-furyl)-4-oxo-4H-1-benzopyran. Photolysis of 6-chloro-3-(1"-cycloalk-2"-enyloxy)-2-[2'-(5-methylfuryl)]-4-oxo-4H-1-benzopyrans. Mechanism of product formation from 3-Cycloalkenyloxybenzopyrans by

• photolysis. Supporting Information Supporting Information File 14: Experimental Data. The data provided represents the yield, melting point, IR, 1H NMR and elemental analysis of the compounds. Acknowledgements We thank UGC, New Delhi for generous financial support for this work.