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
The Ti-mediated reaction of Grignard reagents with nitriles was investigated with sub-stoichiometric amounts of titanium isopropoxide. Cyanoesters were converted to spirocyclopropanelactams in good yields using as low as 0.05 eq of Ti(OiPr)4. Under similar conditions, cyanocarbonates led to spirocyclopropane oxazolidinones and/or aminocyclopropylcarbinols. A very short synthesis of the naturally occurring aminocyclopropanecarboxylic acid illustrates the usefulness of this methodology.