Radicals a to the carbonyl of ethyl 3,4,4-trimethylpentanoate couple w
ith little stereoselectivity while analogous tertiary radicals derived
from ethyl 2,3,4,4-tetramethylpentanoate disproportionate at 25 degre
es C to give the corresponding alkene and alkane. The alkane is formed
by disproportionation with a diastereoselectivity of greater than 20:
1.