Reactions of azulenes with 1,2-diaryl-1,2-ethanediols in methanol in the presence of hydrochloric acid: comparative studies on products, crystal structures, and spectroscopic and electrochemical properties

Abstract Although reaction of guaiazulene ( 1a ) with 1,2-diphenyl-1,2-ethanediol ( 2a ) in methanol in the presence of hydrochloric acid at 60 °C for 3 h under aerobic conditions gives no product, reaction of 1a with 1,2-bis(4-methoxyphenyl)-1,2-ethanediol ( 2b ) under the same reaction conditions as 2a gives a new ethylene derivative, 2-(3-guaiazulenyl)-1,1-bis(4-methoxyphenyl)ethylene ( 3 ), in 97% yield. Similarly, reaction of methyl azulene-1-carboxylate ( 1b ) with 2b under the same reaction conditions as 1a gives no product; however, reactions of 1-chloroazulene ( 1c ) and the parent azulene ( 1d ) with 2b under the same reaction conditions as 1a give 2-[3-(1-chloroazulenyl)]-1,1-bis(4-methoxyphenyl)ethylene ( 4 ) (81% yield) and 2-azulenyl-1,1-bis(4-methoxyphenyl)ethylene ( 5 ) (15% yield), respectively. Along with the above reactions, reactions of 1a with 1,2-bis(4-hydroxyphenyl)-1,2-ethanediol ( 2c ) and 1-[4-(dimethylamino)phenyl]-2-phenyl-1,2-ethanediol ( 2d ) under the same reaction conditions as 2b give 2-(3-guaiazulenyl)-1,1-bis(4-hydroxyphenyl)ethylene ( 6 ) (73% yield) and ( Z )-2-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)-1-phenylethylene ( 7 ) (17% yield), respectively. Comparative studies of the above reaction products and their yields, crystal structures, spectroscopic and electrochemical properties are reported and, further, a plausible reaction pathway for the formation of the products 3 – 7 is described.