Transition-Metal Catalyzed Branched-selective Decarboxylative Heck Reaction

Heck arylation of olefins is an important C-C bond-forming approach that has found wide applications in natural product synthesis,material science,and bioorganic chemistry.Over the past several decades,considerable research efforts have been devoted toward such a transformation and a series of efficient catalyst systems have been established.However,the scope of olefins substrates in these transformations usually suffer from strict limitation due to the fact that the control of its regioselectivity is a challenging issue.Thus far,most of the reported Heck arylations achieve regioselecivity by using actived olefins with an intrinsic electron bias.It is now generally believed that electron-deficient olefins such as acrylates and ketene selectively lead to linear products resulting from coupling at the less-substituted P-position of olefin double bond,while electron-rich olefins such as vinyl ethers and amides favor coupling at the a-position to deliver branched products.But for electronically unbiased olefins,arylation is often troubled by the formation of complicated mixture of linear and branched products with low selectivity,which seriously hampered its applications in organic synthesis.This thesis focus on the regioselectivity of decarboxylative Heck reaction.The following topics were presented in this work:(1)Several kinds of decarboxylative reactions are summarized.(2)We introduce some kinds of Heck reactions briefly and summarize the reports of selectivity Heck reactions.(3)We described the palladium-catalyzed branched-selective decarboxylative Heck reaction from backgrounds,experiment data and results.In conclusion,we have successfully developed a Pd(II)-catalyst system for the decarboxylative Heck reaction of aromatic carboxylic acids with an array of electronically unbiased olefins,which allows highly regioselective formation of less commun branched a-alkyl vinylarenes in good yield.To screen the best condition,we used 2,4-dimethoxybenzoic acid and 1-octene as model reaction.Totally,we developed 31 samples with yield up to 91%and the regioselectivity about branched isomer:linear isomer was up to 8:1.We also proposed the plausible mechanism.Decarboxylative Heck Reaction is an important organic synthetic method.It is still developing.As for our work,so many disadvantages that need to be overcome such as ortho-group limitation,high temperature and poor selectivity for some substrates.That is what we should do in the next.