Knoevenagel condensation of 2-nitrobenzaldehyde with various diketones

CHED 427

Paul Louis Gaus, gaus@wooster.edu, Melinda J. Horst, and Clarissa M. Gage. Department of Chemistry, The College of Wooster, 943 College Mall, Wooster, OH 44691
The condensation of 2-nitrobenzaldehyde with substituted diketones under Knoevenagel conditions (catalyst = piperidine/HOAc) leads to the expected 2-nitrobenzylidene derivatives, with the unexpected formation of substantial amounts of benzofuranyls as well. The formation of the benzofuranyls (for instance 1-(2-benzofuranyl)-ethanone from 2,4-pentanedione and the allyl ester of benzofurancarboxylilc acid from allyl acetoacetate) has proved to be perfectly general, significant amounts of the furanyls being formed in the case of six different substituted diketones. The products of the reaction have been characterized by GC-MS, H-NMR, C-NMR, and 2D-NMR.