Structure for the “Biguaiazulene-3,3′-dione” and Efficient Preparation of 5-Isopropyl-3,8-dimethyl-1,7-azulenedione

Abstract

Abstract The dimeric compound formed from 3-guaiazulenol has been found to be identical with the main product (Q2) of the peracid oxidation of guaiazulene, thus the previous structure of Q2 being revised to be a ca. 1:1 mixture of meso (5R,5′S) and two enantiomeric (5R,5′R and 5S,5′S) forms of [5,5′-biguaiazulene]-3,3′(5H,5′H)-dione. Autoxidation of Q2 in pyridine at 25 °C for 1 d mainly gives the title 1,7-azulenedione.