Directed C–C bond cleavage of a cyclopropane intermediate generated from<i>N</i>-tosylhydrazones and stable enaminones: expedient synthesis of functionalized 1,4-ketoaldehydes
-quaternary centers via regioseletive C-C bond activation has been described. Through cyclopropanation of bench-stable enaminones with in situ generated diazo reagents from N-tosylhydrazones, followed by selective C-C bond cleavage of the cyclopropane ring affords the 1, 4-ketoaldehyde derivatives in good to excellent yields. This method works with broad substrate scope and high regioseletivity.
A highly site-selective acyloxylation of stable enamines with PhI(OAc)2 under metal-free conditions to afford (E)-vinyl acetate derivatives in good to excellent yields is described. Depending on the judicious choice of the solvent system, either the α- or β-site-selective product could be obtained with high selectivity. For the α-site-selective product, the rearranged amide compound is obtained as
A straightforward strategy for synthesis of highly functionalized trifluoromethyl 2H-furans is described. The copper catalyzed method relies on a cascade cyclic reaction between enaminones and N-tosylhydrazones. This method allows the synthesis of 2-amino-3-trifluoromethyl-substituted 2H-furan derivatives carrying a quaternary stereogenic center as single diastereomers. The proposed reaction mechanism
A direct and regiocontrolled thiolation method to access β-amino sulfides through the palladium-catalyzed C(sp2)–H functionalization of stable enamines was described. The reaction was realized under mild conditions by adding an external phosphine ligand to prevent poisoning of the palladium catalyst by the sulfuric reagents. A possible mechanism was proposed according to the obtained results. The DFT
描述了一种通过钯催化的稳定烯胺的 C(sp2)-H 官能化获得 β-氨基硫化物的直接和区域控制的硫醇化方法。该反应在温和条件下通过添加外部膦配体来实现,以防止钯催化剂被硫酸试剂中毒。根据所得结果提出了一种可能的机制。DFT 计算结果与实验数据一致,给出了 β-氨基硫化物的 E 异构体。该反应也以克规模进行,并显示出在有机合成中的潜在应用。
<scp>L</scp>-Proline-Catalyzed Activation of Methyl Ketones or Active Methylene Compounds and DMF-DMA for Syntheses of (2<i>E</i>)-3-Dimethylamino-2- propen-1-ones
作者:Dinesh Kumar、Damodara N. Kommi、Pradeep Chopra、Md Imam Ansari、Asit K. Chakraborti
DOI:10.1002/ejoc.201200778
日期:2012.11
place in the reaction of methylketones or active methylene compounds with DMF-DMA (N,N-dimethylformamide dimethyl acetal). L-Proline serves as an efficient organocatalyst in the covalent and noncovalent synchronous mode for the ambiphilic activation of various aryl, heteroaryl, and styryl methylketones, cyclic ketones, and 1,3-diketones with DMF-DMA to achieve the convenient syntheses of the versatile