Been doing some dithiane chemistry recently and encountered this problem. I was suppose to deprotonate the 1,3-dithiane using nBuLi at -30degC, stir for 2h, followed by addition of my epoxide to the lithiated dithiane solution. However, my lithiated dithiane seems to be "consumed" prior to the addition of my epoxide. Upon work up, i had a lot of unreacted epoxide, very little 1,3-dithiane, and a side product which does not have any of the peaks present in my epoxide. I suspect the side product came from the lithiation of 1,3-dithiane.
What do i mean? Well i did the following:
Dissolve 1,3-dithiane in freshly distilled THF, cool to -30degC, add nBuLi. Stir for 2h. Check TLC. There was a new spot on my TLC, although theoretically i should just see the spot for 1,3-dithiane. Its a spot which stains yellow on CAM stain and runs to a Rf of about 0.3 on 4: 1 (hexane: EA).
Anyone has any such experience or has an insight as to what the side product/side reaction could be?