Synthesis of new chiral spiroacenaphthyl-pyrrolidines/pyrrolizidines :Effect of two important chiral auxiliaries on their stereoselectivities

Chiral spiro pyrrolidines/ pyrrolizidines have brought the surge of interest due to their highly pronounced biological significance and pharmaceutical applications. One of the powerful methods for the synthesis of a variety of natural products containing chiral spiro-pyrrolidine/ pyrrolidines structures is 1,3-DC reaction of azomethine ylides.1 Stereocontrol in these reactions can be achieved through the use of chiral auxiliaries that are attached to the dipolarophiles. In continue of our laboratory purposes in the field of asymmetric 1,3-dipolar cycloaddition reaction (ADCR)2, we report the easy preparation and characterization of new chiral derivatives of spiro pyrrolizidines based on acenaphthoquinone with a highly regio-, diastereo-, and enantioselectivity through of ADCR (Fig. 1). The absolute stereochemistry of cycloadducts, which was obtained by utilizing two types of chiral auxiliaries, was unambiguously established by X-ray crystallography and showed that all cycloadducts have same configuration. They were also clearly the result of endo-re addition of the dipoles to the dipolarophile. The possible mechanism of the reaction was investigated using the DFT approach at the B3LYP/6-311G* level of theory.

Keywords:

Asymmetric 1 , 3-dipolar cycloaddition reaction , Azomethine ylide , Chiral auxiliary , Spiropyrrolizidines