A method for the nucleophilic trifluoromethylation of N-benzoylhydrazones using Me3SiCF3/AcONa has been described. The C=N bond of the hydrazones is activated by difluoroboron group, which is introduced by means of boron trifluoride and allylsilane.
Indium(i) iodide-catalyzed regio- and diastereoselective formal α-addition of an α-methylallylboronate to N-acylhydrazones
作者:Shū Kobayashi、Hideyuki Konishi、Uwe Schneider
DOI:10.1039/b802153h
日期:——
Indium(I) iodide was found to catalyze the formal α-addition of an α-methylallylboronate to various N-acylhydrazones, in the presence of an alcohol additive, to afford the corresponding anti-α-adducts with high regio- and diastereoselectivity in high yields.
Cyanation of N-acylhydrazones using trimethylsilylcyanide (TMSCN) proceeded well in the presence of an amine to afford the corresponding α-hydrazinonitriles in high yields. For less reactive substrates, the combined use of an amine and a catalytic amount of scandium triflate [Sc(OTf)3] was effective to promote the reactions. The mechanistic study suggested that the amine worked as a Brønstedbase
Highly Selective Preparation of Allenic and Homopropargylic Hydrazides through Regiospecific Addition of Propargyltrichlorosilane and Allenyltrichlorosilane to Various Types ofN-Acylhydrazones
作者:Uwe Schneider、Masaharu Sugiura、Shū Kobayashi
DOI:10.1002/adsc.200505379
日期:2006.2
The highlyselectivepreparation of varioustypes of allenic and homopropargylichydrazidesthroughregiospecific allenylation and propargylation of the corresponding N-acylhydrazones is reported. These carbon-carbon bond-forming reactions employing in situ prepared propargyl- and allenyltrichlorosilanes proceed smoothly in N,N-dimethylformamide (DMF) without any metal catalysis (neutral Lewis base
Allyltrichlorosilanes reacted with benzoylhydrazones in DMF without the use of any catalyst to afford the corresponding homoallylic benzoylhydrazines in good to high yields. The reactions proceeded at 0 degrees C to room temperature under mild conditions. In addition, it was found that the reactions tolerated well the steric hindrance of hydrazones and allyltrichlorosilanes. Indeed, ketone-derived
A Simple and General Chiral Silicon Lewis Acid for Asymmetric Synthesis: Highly Enantioselective [3 + 2] Acylhydrazone−Enol Ether Cycloadditions
作者:Seiji Shirakawa、Pamela J. Lombardi、James L. Leighton
DOI:10.1021/ja052307+
日期:2005.7.1
A highly diastereo- and enantioselective [3 + 2] acylhydrazone-enolethercycloaddition mediated by a simplechiralsilaneLewis acid is described. The reactions are highly practical, as demonstrated by a larger scale (5 g of the hydrazone) reaction in which the product was obtained after recrystallization in 93% yield and 99% ee. Evidence for a stepwise mechanism and a model for the asymmetric induction
描述了由简单的手性硅烷路易斯酸介导的高度非对映选择性和对映选择性 [3 + 2] 酰基腙烯醇醚环加成。这些反应是非常实用的,正如更大规模(5 g 腙)反应所证明的那样,其中重结晶后以 93% 的产率和 99% 的 ee 获得产物。还提供了逐步机制的证据和非对称归纳模型。