Vicarious nucleophilic substitution reactions in azolopyridazines controlled by methyl substituents
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- 作者：Anna Katrusiak
- 关键词：Carbanions ; Azolopyridazines ; Sulfones ; Nucleophilic substitution ; Annulation
- 刊名：Tetrahedron Letters
- 出版年：2006
- 出版时间：19 June 2006
- 年：2006
- 卷：47
- 期：25
- 页码：4259-4261
- 全文大小：98 K
文摘
Azolopyridazines, when treated with bromomethyl phenylsulfone in DMSO–t-BuOK at room temperature, yield mainly typical VNS reaction products, while 7-methylazolopyridazines under the same conditions undergo annulation with simultaneous conventional ipso nucleophilic substitution of the chlorine at C6. Consequently, methyl substitution offers a convenient means of controlling the course of VNS carbanion substitution. These competitive reactions illustrate the role of charge distribution and steric hindrance for the course of the nucleophilic substitution, and the methylated azolopyridazines appear to be convenient substrates for highly efficient propose annulation in fused azolopyridazine systems.