REVIEW Ultrasound treatment with LiF in acetonitrile generates an azomethine ylide which undergoes 1,3-dipolar cycloaddition to olefins to give pyrrolidine derivatives in good yield: J. Org. Chem., 52, 235 (1987). Also found use in the the synthesis of 3-carboxy-1-azabicyclo[2.2.1]heptane derivatives, an important class of physiologically active compounds: J. Org. Chem., 66, 2526 (2001).
Padwa, Albert; Journal of Organic Chemistry 1987, V52(2), P235-44