REACTIONS OF GUAIAZULENE WITH PHTHALALDEH YDE, ISOPHTHALALDEHYDE AND TEREPHTHALALDEHYDE IN ACETIC-ACID

The reaction of guaiazulene (1) with a 0.25 molar amount of phthalalde hyde, isophthalaldehyde and terephtalaldehyde in acetic acid at room t emperature (25 degrees C) for 4 h under argon readily gave the corresp onding 3,3'-methylenediguaiazulene having a substituent at C-alpha pos ition (2, 85% yield; 3, 35%; 4, 26%; 5, 92%, respectively). The struct ures of these products were established on the basis of their spectros copic (UV/VIS, IR, NMR and MS) data. A possible reaction pathway for t he formation of these compounds is discussed.