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Complete experimental details for the preparation of dimethyl cubane-1,4-dicarboxylate (1) in multigram quantities, from cyclopentanone (2), in an overall yield of c. 23% are presented.

A moderately yielding (50±4%) method for obtaining 3-methylcyclopent-2-en-1-one from hexane-2,5-dione in ≥99·5% purity was developed, using 2·1% (w/v) of aqueous KOH at reflux. However, the yield was increased to 80±5% by using considerably lower concentrations of base (<0·1%) and higher temperature (200°C) with a conventionally heated autoclave or a microwave batch reactor. The preparation was scaled up with a larger autoclave and also with a continuous flow microwave reactor. The dione impurity was removed from the enone by preferential adsorption on an anion-exchange resin in the bisulfite form. The product was recovered from the aqueous phase with a hydrophobic resin. This environmentally benign, non-extractive isolation method has potential for broad applicability in cleaner production.

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Photophysical and photochemical properties of deazaflavin (3,10-dimethylpyrimido[4,5-b]quinoline- 2,4-(3H,10H)-dione) and some of its 1,5-dihydro derivatives have been investigated. Contrary to earlier reports the photodimer of deazaflavin is non-luminescent throughout the temperature range 77-295 K. Excitation of deazaflavin in the presence of oxalate anion (acetate buffer pH 5.0) causes photodimerization with quantum efficiencies exceeding unity. A mechanism involving a triplet excimer of deazaflavin has been proposed for this reaction.