Hsung and coworkers have developed stereoselective 6p electrocyclic ring-closing reactions of azatrienes. Two classes of azatrienes have been studied: one bearing an allylic stereocenter at C-terminus of the azatriene and another bearing a stereocenter at the N-terminus.1,2 Using QM calculations (B3LYP and M062X), we have explained the selectivities and reactivities observed in these electrocyclizations. Our calculations indicate that stereoselectivity of the electrocyclization of first azatriene class is determined by the inside alkoxy effect, whereas steric effects (allylic strain) control torquoselectivity in the second class of azatrienes. At higher temperatures, this second reaction is reversible, and we have examined the stability of the electrocyclization products in order to explain the product ratio observed when the reaction is under thermodynamic control. 1.         Sydorenko, N.; Hsung, R. P.; et al. Org Lett 2006,  8 (12), 2611-2614.2.         Sklenicka, H. M.; Hsung, R. P.; et al. J Am Chem Soc 2002,  124 (35), 10435-10442.

Reactivity and torquoselectivity in the electrocyclizations of chiral 1-azatrienes

244th National Meeting (2012)

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