Pd‐Catalyzed Zn‐ene allylic olefinations with the new ethylzinc reagents Et-Zn-OSO₂CF3 (4) and Et-Zn-OC(O)CF(MeO)CF₃ (5) in CH₂Cl₂ showed an unexpected trans‐selectivity in the ring closure to cyclopentane derivatives (see Scheme 2 and Table 1). This strong trans‐selectivity is in contrast with the corresponding known Zn‐ene reaction using Et₂Zn in Et₂O which shows a high cis‐selectivity (Table 1). The probable radical origin of the observed trans‐selectivity is discussed. The Zn‐ene reaction products of the type R-Zn-OSO₂CF₃ could be derivatized by the known protonation, iodination, and cyanation yielding 8–10 (Scheme 4 and Table 2), these derivatizations could furthermore be extended by allylation and oxidation reaction (→ 13, 15, and 16; see Scheme 5).