Allylic C-H functionalization of simple alkenes stands as a straightforward and step-efficient method for synthesizing functionalized alkenes. Over the past two decades, significant advancements have been made in this field. Mechanistically, two distinct pathways were proposed in these transformations. The first involves Pd-catalyzed allylic C-H activation of α-alkenes with the aid of external oxidants, producing electrophilic allylic Pd(II) intermediates, which are then intercepted by a wide range of "soft" nucleophiles (Scheme 1a). The second approach involves forming nucleophilic allylic metal intermediates by the use of late-transition metals (such as Fe and Co) 2 and alkali metals (for instances, Li and Na) under basic conditions, which subsequently add to carbonyl compounds and imines (Scheme 1b). Despite these impressive achievements, the direct C-H functionalization of internal alkenes remains an open question due to the low reactivity as well as the regioselectivity and stereoselectivity. Furthermore, expanding the range of coupling partners of the above allyl metal intermediates will undoubtedly enhance the application of allylic C-H functionalization in organic synthesis.