Accessing N-Stereogenicity through a Double Aza-Michael Reaction: Mechanistic Insights

作者：Kohrt Sonja; Santschi Nico; Cvengros Jan

来源：Chemistry - A European Journal, 2016, 22(1): 390-403.

DOI：10.1002/chem.201502670

• asymmetric synthesis
• Michael addition
• diastereoselectivity
• stereogenicity
• Troger base

Further development of the chemistry and applications of chiral compounds that possess configurationally stable stereogenic nitrogen atoms is hampered by the lack of efficient strategies to access such compounds in an enantiomerically pure form. Esters of propiolic acid and chiral alcohols were evaluated as cheap and readily available Michael acceptors in a diastereoselective synthesis of N-stereogenic compounds by means of a double aza-Michael conjugate addition. Diastereomeric ratios of up to 74: 26 and high yields were achieved with (-)-menthyl propiolate as a substrate. Furthermore, a detailed mechanistic investigation was undertaken to shed some light on the course of this domino transformation. Kinetic studies revealed that the protic-solvent additive acts as a Bronsted acid and activates the ester toward the initial attack of the tetrahydrodiazocine partner. Conversely, acidic conditions proved unfavorable during the final cyclization step that provides the product.

• 出版日期2016-1-4