101. Practical preparation and metallo-ene reactions of (2-alkenylallyl)-magnesium chlorides: Comparative study of magnesium activation
     Oppolzer, W.; Schneider, P.
     Tetrahedron Lett. 1984, 25, 3305-3308

Magnesium activated by equilibration with its anthracene adduct in THF metalates smoothly 2-alkenyl chlorides at −65°C without significant coupling. The resulting solutions of Grignard reagents are subjected to thermal (80–130°C) cyclization followed by trapping with electrophiles.

DOI : 10.1016/S0040-4039(01)81370-8