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The 1,3-azole motif is a common and integral feature of many clinical drugs. Due to their wide-ranging applications, the development of 1,3-azoles as therapeutic agents is an ongoing focus of medicinal chemists. This review highlights the recent approaches towards the assembly of 1,3-oxazole, 1,3-thiazole and 1,3-imidazole motifs.

Model studies dealing with the Cu(II)- or Rh(II)-catalyzed carbenoid cyclization/cycloaddition cascade of several α-diazo indolo amido esters have been carried out as an approach to the alkaloid scandine. The Cu(II)-catalyzed reaction of an α-diazo indolo diester that contains a tethered oxa-pentenyl side chain was found to give rise to a reactive benzo[c]furan which undergoes a subsequent [4 + 2]-cycloaddition across the tethered π-bond. The reaction proceeds by the initial generation of a copper carbenoid intermediate which cyclizes onto the adjacent carbonyl group to give a reactive benzo[c]furan which in certain cases can be isolated. Disappointingly, the analogous reaction with the related amido indolo ester failed to take place, even when the tethered π-bond contained an electron-withdrawing carbomethoxy group. It would seem that the geometric requirements for the intramolecular cycloaddition of the furo[3,4-b]indole system with the tethered π-bond imposes distinct restrictions upon the bond angles of the reacting centers to prevent the cycloaddition reaction from occurring. However, the incorporation of another carbonyl group on the nitrogen atom of the tethered alkenyl diazo amido indolo ester seemingly provides better orbital overlap between the reacting π-systems and allows the desired cycloaddition reaction to occur.

The application of oxidative dimerization for the biomimetic synthesis of balsaminone A and ellagic acid is described. Balsaminone A is synthesized via the oxidative dimerization of 1,2,4-trimethoxynaphthalene under anhydrous conditions using CAN, PIDA in BF3 ·OEt2 or PIFA in BF3 ·OEt2 in 7–8% yields over 3 steps. Ellagic acid is synthesized from its biosynthetic precursor gallic acid, in 83% yield over 2 steps.