Abstract
Chiral nonracemic aminated nitroso acetals were synthesized via diastereoselective multicomponent [4 + 2]/[3 + 2] cycloadditions employing new (S,E)-γ-nitrogenated nitroalkenes 5a–c as heterodienes, ethyl vinyl ether (EVE) as a dienophile, and selected electron-deficient alkenes as 1,3-dipolarophiles. The employment of different organic solutions of LiClO4 or LiCl as promoter systems provided the respective nitroso acetals with yields from 34–72% and good levels of diastereoselectivity. In addition, the nitroso acetal 9c was transformed to the pyrrolizidin-3-one derivative 14c, proving the usefulness of the route in the synthesis of an interesting chiral compound. The elucidation of the stereostructures was based on 2D COSY, NOESY and HSQC NMR experiments as well as an X-ray diffraction experiment.
Highlights
Conjugated nitroalkenes play an important role in cycloaddition reactions providing useful nitrogenated cycloadducts with varied synthetic applications (Scheme 1) [1,2,3]
In an exploratory study to screen the best solvent system, the reactivity of 5a,b with ethyl vinyl ether (EVE) and methyl acrylate (MA) as a dipolarophile was evaluated in the absence of a promoter
The cycloadducts were obtained in 18–70% yield with total chemo- and regioselectivity including good levels of diastereoselectivity (Table 1)
Summary
Conjugated nitroalkenes play an important role in cycloaddition reactions providing useful nitrogenated cycloadducts with varied synthetic applications (Scheme 1) [1,2,3]. Denmark’s group and others investigated the tandem [4 + 2]/[3 + 2] nitroalkene cycloaddition employing unactivated olefins or enol ethers as dienophiles and electron-deficient alkenes as 1,3-dipolarophiles to furnish nitroso acetals of type 4 in an inter- or intramolecular fashion [1,2,3,8,9].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
