Synthesis of Functionalized Pyridazin-3(2H)-ones via Selective Bromine鈥揗agnesium Exchange and Lactam Directed Ortho C鈥揌 Magnesiation
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- 作者：Tom Verhelst ; Jens Maes ; Zuming Liu ; Sergey Sergeyev ; Bert U. W. Maes
- 刊名：Journal of Organic Chemistry
- 出版年：2011
- 出版时间：August 19, 2011
- 年：2011
- 卷：76
- 期：16
- 页码：6670-6677
- 全文大小：906K
- 年卷期：v.76,no.16(August 19, 2011)
- ISSN：1520-6904
文摘
Selective bromine鈥搈agnesium exchange on 2-benzyl-5-bromo-4-methoxypyridazin-3(2H)-one could be achieved when MesMgBr was used as reagent. With more nucleophilic RMgCl species (R = Bu, i-Pr, Ph) both nucleophilic addition鈥揺limination at C-4 and bromine鈥搈agnesium exchange at C-5 occurred. In 2-benzyl-5-bromopyridazin-3(2H)-one, which does not contain a substituent at C-4, addition could not be suppressed. Less nucleophilic Mg amides (TMPMgCl路LiCl) allowed regioselective C鈥揌 magnesiation at the C-4 position in such substrates, as exemplified for 2-benzyl-5-chloro- and 2-benzyl-6-chloropyridazin-3(2H)-one. Quenching of the magnesiated pyridazinones with electrophiles gives access to a variety of hitherto unknown pyridazin-3(2H)-one derivatives.