Preparation and pyrolysis of 1-(pyrazol-5-yl)-1,2,3-triazoles and related compounds 1
作者:David Clarke、Richard W. Mares、Hamish McNab
DOI:10.1039/a700421d
日期:——
1-(Pyrazol-5-yl)-1,2,3-triazoles 8a, 9a and 10 are prepared by
cycloaddition of 5-azidopyrazoles with methyl prop-2-ynoate. The
regiochemistry of the process is confirmed by synthesis of 9a using an
authentic route from ethyl 2-formyl-2-diazoacetate 13. Flash vacuum
pyrolysis of 8a, 9a and 10 gives
5-methoxypyrazolo[1,5-a]pyrimidin-7-ones 16–18 by a
mechanism involving an unexpected oxoketenimine–imidoyl ketene
rearrangement as the key step. The mechanism is supported by a
13C labelling experiment. A general route to
pyrazolo[1,5-a]pyrimidin-7-ones from pyrazolylaminomethylene
Meldrum's acid derivatives (e.g. 30–32) is also
reported.
1-(吡唑-5-基)-1,2,3-三唑 8a、9a 和 10 是通过 5-叠氮吡唑与 2-丙炔酸甲酯的环加成反应制备的。利用 2-甲酰基-2-重氮乙酸乙酯 13 的正宗路线合成 9a 证实了这一过程的区域化学性。通过对 8a、9a 和 10 进行闪速真空热解,得到 5-甲氧基吡唑并[1,5-a]嘧啶-7-酮 16-18。该机制得到了 13C 标记实验的支持。此外,还报道了从吡唑氨甲基梅氏酸衍生物(如 30-32)制备吡唑并[1,5-a]嘧啶-7-酮的一般路线。