78748-84-2Relevant academic research and scientific papers
Thermal Azulene Rearrangements. Synthesis and Thermolysis of Azulene
Gugel, Hansjoerg,Zeller, Klaus-Peter,Wentrup, Curt
, p. 2775 - 2784 (2007/10/02)
A specific synthesis of azulene (24) is described.The synthetic sequence outlined in scheme 3 begins with the construction of toluene (17) which is performed in 8 steps starting from paraformaldehyde.The suspected scrambling of the label in the dehydrogenation step 16 -> 17 can be suppressed by suitable reaction conditions.After extension of the side chain by 3 carbon atoms to give 1-diazo-4-(phenyl)-2-butanone (21), the labelled azulene is obtained according to Scott's azulene synthesis (21 -> 22 -> 23 -> 24).The vacuum thermolysis of24 (1050 deg C, 10-3 - 10-2 torr) yields naphthalene (25) as the main product (91 percent of the naphthalene formed) in accordance with the norcaradiene-vinylidene mechanism.The remaining 9 percent consist of naphthalene.Besides the formation of naphthalene (15 percent conversion), 24 suffers automerisation to a small extent yielding - and azulene (ca. 3 and 1 percent, respectively).
