Radical Arylation Reactions of 4, 6, 8‐Trimethylazulene

The synthesis of 1‐ and 2‐aryl‐substituted (aryl = Ph, 4‐NO 2 C 6 H 4 , and 4‐MeOC 6 H 4 ) 4, 6, 8‐trimethylazulenes ( 4 and 3 , respectively) in moderate yields by direct arylation of 4, 6, 8‐trimethylazulene ( 8 ) with the corresponding arylhydrazines 13 in the presence of Cu II ions in pyridine (see Scheme 4 ) as well as with 4‐MeOC 6 H 4 Pb(OAc) 3 ( 16 ) in CF 3 COOH (see Scheme 5 ) is described. With 13 , also small amounts of 1, 2‐ and 1, 3‐diarylated azulenes (see 14 and 15 , respectively, in Scheme 4 ) are formed. The 4‐methoxyphenylation of 8 with 16 yielded also the 1, 1′‐biazulene 17 in minor amounts (see Scheme 5 ). 4, 6, 8‐Trimethyl‐2‐phenylazulene ( 3a ) was also obtained as the sole product in moderate yields by the reaction of sodium phenylclopentadienide ( 1a ) with 2, 4, 6‐trimethylpyrylium tetrafluoroborate ( 2 ) in THF ( Scheme 1 ). The attempted phenylation of 8 as well as of azulene ( 9 ) itself with N ‐nitroso‐ N ‐phenylacetamide ( 10 ) led only to the formation of the corresponding 1‐(phenylazo)‐substituted azulenes 12 and 11 , respectively ( Scheme 3 ).