Direct construction of novel dispiro heterocycles through 1,3-dipolar cycloaddition of azomethine ylides

The 1,3-dipolar cycloaddition of 2-oxo-(2H)-acenaphthylen-1-ylidene-malononitrile and 2-fluoren-9-ylidene-malononitrile as dipolarophiles have been investigated for the first time with the azomethine ylides generated in situ from N-substituted isatin and sarcosine to furnish novel dispiro heterocycles. The structure and relative stereochemistry of both types of cycloadducts were confirmed by single crystal X-ray diffraction, as well as with the help of H-1, C-13, and HMBC spectroscopic methods. (C) 2011 Elsevier Ltd. All rights reserved.