US EPA

6838584 

Journal Article 

AuBr 3 -Catalyzed [4 + 2] Benzannulation between an Enynal Unit and Enol 

Asao, N; Aikawa, H; Yamamoto, Y; , 

2004 

Yes 

Journal of the American Chemical Society
ISSN: 0002-7863
EISSN: 1520-5126 

126 

24 

7458-7459 

English 

15198590 

10.1021/ja0477367 

https://pubs.acs.org/doi/10.1021/ja0477367
Exit
 

The reaction of enynals 1, including o-alkynylbenzaldehydes, and carbonyl compounds 2 in the presence of a catalytic amount of AuBr3 in 1,4-dioxane at 100 degrees C gave the functionalized aromatic compounds 3 in high yields. The AuBr3-catalyzed formal [4 + 2] benzannulation proceeds most probably through the coordination of the triple bond of 1 to AuBr3, the formation of a pyrylium auric ate complex via the nucleophilic addition of the carbonyl oxygen atom, the reverse electron demand-type Diels-Alder addition of the enols, derived from 2, to the auric ate complex, and subsequent dehydration and bond rearrangement. Similarly, the AuBr3-catalyzed reactions of 1 with acetal compounds afforded the corresponding aromatic compounds in good yields.