Molecular Transformation of 2‐Methylazulenes: An Efficient and Practical Synthesis of 2‐Formyl‐ and 2‐Ethynylazulenes. Issue 9 (5th March 2018)

• Record Type: Journal Article
• Authors: Shoji, Taku; Araki, Takanori; Iida, Nanami; Kobayashi, Yoshiaki; Ohta, Akira; Sekiguchi, Ryuta; Ito, Shunji; Mori, Shigeki; Okujima, Tetsuo; Yasunami, Masafumi
• Is Part Of: European journal of organic chemistry. Issue 9(2018)
• Page Start: 1145
• Page End: 1157
• Publication Date: 2018-03-05
• Subjects: Hydrocarbons -- Azulenes -- Formylation -- Alkynylation -- Cross‐coupling -- UV/Vis spectroscopy; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201701746
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract : 2‐Formylazulene derivatives have been obtained in good yields by the reactions of 2‐methylazulenes with N, N ‐dimethylformamide dimethyl acetal, followed by oxidative cleavage of the intermediately formed enamines with NaIO4 . Vilsmeier formylation of 1‐phenyl‐3‐methylazulenes also afforded the corresponding 2‐formylazulenes in moderate yields. The treatment of a 2‐methylazulene derivative bearing a formyl group at the 1‐position with sodium methoxide led, through a self‐condensation reaction, to a trans ‐1‐(azulen‐1‐yl)‐2‐(azulen‐2‐yl)ethylene derivative, the structure of which was verified by single‐crystal X‐ray diffraction analysis. The 2‐formylazulenes obtained were transformed into 2‐ethynylazulenes in good yields by a modified Seyferth–Gilbert reaction. The reactivity of a 1‐iodoazulene bearing a 2‐formyl function in palladium‐catalyzed cross‐coupling reactions has also been examined. Abstract : 2‐Formylazulene derivatives have been obtained in good yields by the reactions of 2‐methylazulenes with N, N ‐dimethylformamide dimethyl acetal, followed by oxidative cleavage of the intermediately formed enamines with NaIO4 . The 2‐formylazulenes obtained were transformed into 2‐ethynylazulenes in good yields by a modification of the Seyferth–Gilbert reaction.