Titanium-Mediated Addition of Grignard Reagents to Acyl Cyanohydrins: Aminocyclopropane versus 1,4-Diketone Formation
作者:Paul Setzer、Gwénaël Forcher、Fabien Boeda、Morwenna S. M. Pearson-Long、Philippe Bertus
DOI:10.1002/ejoc.201301251
日期:2014.1
The 1,2-dianion reactivity of the reagent generated from EtMgBr and titanium isopropoxide was illustrated when N-acyl cyanohydrins were used as substrates (>20 examples), giving both aminocyclopropane derivatives and 1,4-dicarbonyl compounds. When the reaction was performed in diethyl ether, 5-hydroxy-1,4-diketones were the main product. Under specific conditions (use of tetrahydrofuran and a bulky
product was modulated by kinetic control, giving selectively hydroxyamides or cyclic carbamates. Allylzinc reagents were used to access highly functionalized tertiary carbinamine derivatives in high yields from cyanoesters and cyanocarbonates. While the monoaddition of organometallics on nitriles is generally observed, in this work the nucleophilic allylation occurs twice, due to an intermediate transfer
including the particularly simple divinylglycine, which is not easily accessible by using conventional methods. A straightforwardsynthesis of symmetrically α,α-disubstituted α-amino acids is presented. The key step of this process relies on the efficient double addition of Grignard reagents to acyl cyanohydrins to provide N-acyl amino alcohols selectively in good yields. The chemoselectivity of the reaction
Exploring the Steric and Electronic Factors Governing the Regio- and Enantioselectivity of the Pd-Catalyzed Decarboxylative Generation and Allylation of 2-Azaallyl Anions
作者:Shuaifei Wang、Xiaoyan Qian、Yuanyu Chang、Jiayue Sun、Xiujing Xing、Wendy F. Ballard、Jason J. Chruma
DOI:10.1021/acs.joc.8b00491
日期:2018.4.6
The impact of the steric and electronic factors in both the para-substituted benzaldimine and 2,2-diarylglycine components on the regioselectivity and enantioselectivity of the palladium-catalyzed decarboxylative allylation of allyl 2,2-diarylglycinate aryl imines was explored. These studies revealed that using 2,2-di(2-methoxyphenyl)glycine as the amino acid linchpin allowed for the exclusive synthesis