Mechanistic studies were attempted to elucidate the reaction mechanism of this reaction (Figure ). First, cyclopropylmethanol (84) and 4-vinyltoluene (85) were reacted using the standard conditions for this reaction (Table ). In consequence, the ring opening radical 86 was obtained. The Giese reaction of the chiral compound 87 with styrene (41) gave the racemic compound 77. From these experimental results, it is clear that this reaction is a radical reaction mechanism.