Nitrogen bridgehead compounds. Part 45 [1]. Synthesis of 6‐arylhydrazono‐6,7,8,9‐tetrahydro‐11 H ‐pyrido‐[2,1‐ b ]quinazolin‐11‐ones

A series of 6‐arylhydrazono‐6,7,8,9‐tetrahydro‐11 H ‐pyrido[2,1‐ b ]quinazolin‐11‐ones 3–37 , conveneint starting materials for indolopyridoquinazolines, were prepared by diazonium coupling between aryldiazonium chlorides and 6,7,8,9‐tetrahydro‐ 2 , 6‐formyl‐5,7,8,9‐tetrahydro‐ 39 , 6‐(dimethylamino)methylene‐6,7,8,9‐ 38 or 6‐carboxyl‐5,7,8,9‐tetrahydro‐11 H ‐pyrido[2,1‐ b ]quinazolin‐11‐ones 43 . The arylhydrazono derivatives were also prepared from 6‐bromo‐ 45 or 6,6‐dibromo‐6,7,8,9‐tetrahydro‐11 H ‐pyrido[2,1‐ b ]quinazolines 46 with arylhydrazines. The structures of the 6‐arylhydrazonopyridoquinazolines were characterized by uv and 1 H nmr spectroscopy. The 6‐arylhydrazono derivatives show a solvent‐dependent E‐Z isomerism.