Organic Communications Articles

Photochemical reactions of some 3-allyloxy-2-phenylchromones have been studied. Photoreactions of the compounds afforded substituted pyronopyrane derivatives through the 1,4-biradicals.

Bridged ortho esters of 3-halopropyl carboxylic acids were prepared by esterification of 3-methyl-3-hydroxymethyloxetane with 3-bromopropionyl chloride and pyridine in dry THF, followed by rearrangement with boron trifluoroetherate, to afford 1-(2-bromoethyl)-4-methyl-2,6,7-trioxabicyclo[2,2,2]-octane. The 1-(2-iodoethyl)-4-methyl-2,6,7-trioxabicyclo[2,2,2]-octane analogue could not be prepared directly by halogen exchange of 1-(2-bromoethyl)-4-methyl-2,6,7-trioxabicyclo[2,2,2]-octane but could be prepared by halogen exchange of the (3-methyloxetan-3-yl)methyl 3-bromopropanoate with a mixture of sodium iodide and anhydrous sodium sulfate in acetone, followed by rearrangement with boron trifluoroetherate.

12,13-Dibromometa[2](2,5)thiophenophane was subjected to Suzuki-Miyaura cross coupling to yield 12,13-diarylmeta[2](2,5)thiophenophanes, cyclophanes with extended p -systems.

High-yielding syntheses of two unpublished series of amino-1,5-benzodiazepines derivatives 3 and 1,2,3-benzotriazoles 4 bearing a dimedone moiety are respectively reported. Derivatives 3 were obtained by intramolecular cyclisation using cyanogenbromide of enaminone 2. On the other hand, when enaminones 2 were treated with sodium nitrite under acidic conditions, cyclisation led to benzotriazole 4.