Research On Synthesis Of 1,3-Dienes Based On Oxyacetamide Directing Group

In recent years,the activation of C-H bonds involving transition metals has attracted much attention.It can efficiently construct a series of C-C bonds or C-X(X=N,O,P,S,Se,Br,etc.)bonds under mild reaction conditions,and is successfully used to synthesize natural products and drug molecules.However,the site selectivity of the reaction is still the biggest challenge currently facing.The general solution is to introduce a directing group on the substrate,but this undoubtedly adds steps to the post-processing of the reaction system,hence the development of easily attachable and detachable directing groups is needed.Among the many directing groups,the Oxyacetamide group(-ONHAc)stands out with its overwhelming advantages.It is a kind of traceless directing group.The cleavage of O-N bond can act as an internal oxidant without the addition of an external oxidant.At the same time,it can be converted into a variety of compounds,so it has become a commonly used directing group in research.1,3-dienes is an important type of skeletons,which is widely exist in numerous natural products and bioactive compounds.The synthesis of these compounds has many shortcomings such as tedious steps and poor selectivity,but transition metal-catalyzed C-H bond functionalization may become a new strategy to solve these problems.In many researchs,Oxyacetamide(-ONHAc)has been widely used as a directing group for functionalization of aryl C(sp~2)-H bonds,but the examples involving the functionalization of alkenyl C(sp~2)-H bonds remain scarce.Considering the importance of selective alkenyl C-H bond functionalization,we combined oxyacetamide with olefins and developed a Cp*Rh(Ⅲ)-catalyzed C-H bond functionalization atβ-position of Z-type olefins.With-ONHAc as the directing group,multisubstituted 1,3-dienes were prepared through a rare exo-rhodacycle process.This method has good applicability to a variety of olefins coupling partners and has high regioselectivity.Such a method can also be used to modify drug molecules and selectively separate olefin compounds with Z/E structure.In addition,the dienoate products can be efficiently converted into the correspondingβ-amino acid,which provides a new strategy for the synthesis ofβ-amino acid.