Rh-catalyzed Isomerization And Dehydrogenative Borylation Of Olefins

Alkenes are widely found in natural products and medicines,and play an important role in organic synthesis.In the past few d ecades,in order to build new carbon-carbon double bonds,a lot of research has been carried out about the traditional Witting reaction,olefin metathesis reaction,and alkyne hemihydro reduction.It has been found that E/Z mixed configurations are usually formed during the reaction.Because the polarities of the two configurations of olefins are not significantly same,Olefins are separated difficultly.T he chemical properties of the two configurations of olefins are also different.T herefore,new methods for synthesizing pure olefins have been explored in the research process of organic synthesis.Isomerization of olefins is a kind of simple,efficient,environmentally friendly,and highest atomic utilization method to achieve this goal.It is necessary to find such a new method that is complementary to existing methods.Alkenyl borates are very important reaction intermediates in organic synthesis,and are often used to synthesize a variety of organic molecules,natural compounds,and biological materials.They can be used to build effective carbon-carbon and carbon-heteroatoms key.Reductive boration of alkynes and Miyaura boration of haloalkanes are common methods for the synthesis of alkenyl borates.However,they all face the problems of selectivity and narrow source of raw materials.T herefore,it is an efficient and simple method to directly obtain target product through the dehydroboration reaction,but it often faces the problem that a large number of by-products are generated during the reaction.T herefore,the realization of stereoselective synthesis of alkenyl borates from simple and easily available olefins has very important research value.This article explored the isomerization and dehydroboration of olefins under the reaction conditions of rhodium catalysts,phosphine ligands and alkalis using olefin E/Z mixture as raw materials.T he advantages of the reaction:（1）T he reaction conditions are mild,and the range of substrates is very broad;（2）Good selectivity and high atomic utilization;（3）It can be applied to the synthesis of natural medicines and has a wide range of applications.T he details are as follows:1.A simple method has been explored to produce thermodynamically stable olefins in high yield and high ratio.T his reaction is based on E/Z-mi xed olefins using[Rh（cod）Cl]₂ as catalyst,Xantphos as ligand,and DME as solvent.In the presence of a small amount of B ₂Pin₂,it was stirred at 60℃ for 8 hours.T he substrates with a range of electronically diverse substituents at the para-position,alkyl substituents,and stilbene derivatives were studied for substrate extension,it was found that the reaction has good substrate suitability and functional group compatibility.2.Explore a new method to synthesize alkenyl borates.（E/Z）-1-phenyl-1-pentene was used as the reactant,Li₃PO₄ as the base,and DME as the solvent.T he mixture was stirred at 80°C for 16 h in the presence of 1.1 eq B₂Pin₂.T his reaction has mild reaction conditions,good substrate applicability and functional group compatibility.