Recent advances in positional-selective alkenylations: removable guidance for twofold C-H activation

The transition metal-catalyzed transformation of otherwise inert C-H bonds into substituted alkenes offers a versatile tool for the synthesis of value added olefinic molecules. Recent developments in the directing group assisted C-H activation approach ensured high levels of positional selectivity. A vast number of coordinating groups have been utilized in directed C-H alkenylation, which are often not removable after the desired transformation. However, the concept of easily removable or traceless directing group strategy overcomes this limitation and enables site-selective C-H alkenylation of relevance to academia and the practitioners in industry. Various easily removable or transformable directing groups utilized in the transition metal-catalyzed oxidative C-H alkenylations are discussed in this review until February 2017.