Synthesis of 1-(2-benzofurancarbonyl)azulenes using 1-(bromoacetyl)azulenes as new building blocks
作者:Satoko Yamashiro、Kimiaki Imafuku
DOI:10.1002/jhet.5570390411
日期:2002.7
afford 1-acetyl-3-bromoazulene (3) and 3-bromo-1-(bromoacetyl)azulene (4). In a similar manner, 3-methyl-, 3-ethyl-, 3-propyl-, and 3-methoxycarbonyl-substituted 1-acetylazulenes 2a-d gave the corresponding 3-substituted 1-(bromoacetyl)azulenes 5a-d as major products and 1-(dibromoacetyl)azulenes 6a-d as minor ones. The 1-(bromoacetyl)azulenes 5a-d are useful as new building blocks. Compounds 5a-d reacted
1-(Bromoacetyl)-3-methylazulene (1a) and methyl 3-(bromoacetyl)azulene-1-carboxylate (1b) reacted with thioamides 3a,b and thioureas 3c,d in boiling ethanol to give the corresponding (4-thiazolyl)azulenes 4a-d and 5a-d in good yields, respectively. The reactions of dibromoacetyl-substituted azulene (2) also gave (4-thiazolyl) azulenes 5a-d in lower yields and the azulene 2 was recovered. By heating
with sodium monobromoisocyanurate (SMBI) (1) to give 3‐bromo‐substituted azulenes 5 and 6, respectively. The brominations in dichloromethane gave the brominated products in low yields, while the reactions in dichloromethane–water gave the products in high yields. This indicates that SMBI (1) was hydrolyzed in the presence of water to generate hypobromic acid, which accelerated the bromination as a