Synthesis of unsymmetrical hetaryl-1,2-diketones

Oxidation of the triple bond in 4-alkynylpyrazoles 2a-e and acetylenic derivatives of the crown-ethers 7a,b with PdCl2-DMSO has been carried out to give unsymmetrical hetaryl-1,2-diketones 3a-e; 8a,b. Attempts to oxidize the triple bond in 5-alkynylpyrazole 6 and alkynylpyridines 5a,b and 9 failed. (C) 2002 Elsevier Science Ltd. All rights reserved.