Ok, I looked up the reference today (Tet. Lett. 19, 1627 (1977) T.-C. Choong, H. R. Shough). And that's indeed what they did!
I just wonder why this article is only partially indexed in Beilstein, while the next article in that volume is completely in there
.
You can't calculate the amount of activated manganese dioxide in this kind of oxidations. Remember that you are using a suspended solid MnO
2. A rule of thumb is to use 10 to 20 equivalents by weight.
BTW, the second reaction is cyanide-catalyzed
.