Oxidation Of Alkynyl Boronates And Dehydroboration Of Silyl Enol Ethers

The synthesis and application of organoboron compounds are an extremely important branch of organic chemistry,and organoboron compounds have been used to synthesize and modify various organic functional molecules such as drugs,natural products and agrochemical.As two unique organic boron compounds,alkynyl borates and alkenyl borates have various reactivities due to thier unsaturated bonds and carbon-boron bonds.Focusing on the synthesis and application of organoboron compounds,this thesis will introduce the oxidation of alkynylborates and dehydroboronation of enol silyl ethers.It compose the following two parts:In the first part of the work,we developed a new method for preparation of carboxylic acids by oxidation of alkynyl pinacol borates with potassium peroxymonosulfonate（Oxone）.We utilized terminal alkynes as raw materials to synthesize alkynyl borates.After simple work up,the next step of oxidation can be carried out without further purification.In the oxidation process,oxone was employed as oxidant,acetone and water as solvent.The mixtures were allowed to stir at 50℃for overnight to obtain carboxylic acid in good to excellent yield s.The reaction conditions are mild,and the range of substrates is very broad.The alkynyl borates derived from alkynes containing various functional groups can be oxidized to carboxylic acids.We have successfully synthesized a variety of drugs containing carboxyl groups from corresponding alkynes substrates under the optimized conditions,demonstrating the excellent synthetic potential of this method.We have also performed some mechanistic studies and gained a preliminary understanding of this oxidation process.In the second part of the work,a rhodium-catalyzed dehydroboronation reaction using enol silyl ethers derived from acetophenone as raw material was presented,.Using[Rh（cod）Cl]₂ as the catalyst,Xantphos as the ligand and B ₂pin₂ as the boron reagent,the dehydroboronation of enol silyl ether was successfully achieved at 70℃for 12 hours in the tetrahydrofuran.We examined the generality of this reaction and found that enol silyl ethers containing electron withdrawing or electron donating groups were accommodated to obtain target products in moderate to good yields under this conditions.This transformation is expected to play a role in the modification and synthesis of biologically active molecules,natural products and drugs.This thesis introduces the oxidation reaction of alkynyl borate s and the dehydroboration reaction of silyl enol ether s.After screening and determinig the best reaction conditions,the scope of the two reactions has been investigated and high functional group tolerance was demonstrated.Of note,the method is expected to play a role in the synthesis and modification of natural products and drugs.