Preparation of Heteroaromatic Derivatives

Azido esters such as 10 are readily prepared from the corresponding aldehyde by phos-phonate condensation. Shunsuke Chiba and Koichi Narasaka of Nanyang Technology University demonstrated (Organic Lett. 2008, 10, 313) that thermal condensation of 10 with acetyl acetone 11 gave the pyrrole 12, while Cu catalyzed condensation with acetoac-etate 13 gave the complementary pyrrole 14. 

Each of these approaches depended on the availability of the ortho-substituted aniline starting materials. Junbiao Chang and Kang Zhao of Tianjin University devised (/. Org. Chem. 2008, 73, 2007) a complementary approach, the cyclization of 29 to 30, in the process directly aminating the benzene ring. Marijan Kocevar of the University of Ljubljana established Tetrahedron 2008, 64, 45) an alternative Diels-Alder approach to indoles, combining 31 and 32 to give 33. 

The preparation of p Tidines will be covered in the next column on heteroaromatic construction. 

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