5-exo-Selective reductive Mizoroki-Heck reaction of 4-tert-butyl-l-chlorobenzene with 2,5-norbornadiene has been achieved by [PdCl2(PCy3)(2)]/HCO2Na to give 5-exo-(4-tert-butylphenyl)-2-norbornene in 95% yield. When Cs2CO3 is used as a base in the absence of a reducing reagent, an exo-benzocyclobutene-fused norbomene, 6-tert-buty1-1,4,4a,8b-tetrahydro-1,4-methanobiphenylene is produced in 62% yield.