Iron-catalyzed Hydroboration Of Alkynes

Alkenyl boron compounds are important organoboron compounds and are excellent intermediates for organic synthesis.They have a wide range of applications in the construction of C-C bonds and C-X(X=O,N,S,etc.),for example,Suzuki-Miyaura cross-coupling reaction,Chan-Lam coupling reaction and C-B bond reduction reaction,and the like.Therefore,the synthesis of alkenyl boron compounds has always been of great concern to scientists.The existing methods for synthesizing an alkenyl boron compound mainly include(i)Metal transfer of alkenyl metal magnesium or lithium reagents with trialkyl boronates;(ii)Transition metal-catalyzed alkyne hydroboration;(iii)Grubbs metathesis reaction of alkenyl boron with olefins;(iv)Heck coupling reaction ofhaloboronic acid esters with olefins.Among them,the hydroboration of alkynes is the most direct and most important method for the production of alkenyl boron compounds.Precious metal catalysts such as Pt,Rh,Ir,etc.show very high activity in the hydroboration of olefins;In recent years there have also been many reports of Cu-catalyzed alkyne hydroboration reactions to produce alkenyl boron compounds.There are also a few examples of iron-catalyzed alkyne hydroboration reactions.These reactions require the use of ligands,and the ligands used generally require multiple steps.Synthetic,non-commercial reagents;Second,when boron bis(pinacolato)diboronate(B2pin2)is used as a boration agent,the formation of polyboride products is a problem.For non-terminal alkynes,there are also problems with regioisomers.Based on the above deficiencies,in this study,we used the new boronate mono-triol boron salt developed by Prof.Yamamoto of Hokkaido University of Japan as a boronation reagent to carry out low-cost,non-toxic ferrous salt-catalyzed alkyne and alkyne.In the study of the hydroboration reaction,we found that the monoborane monoborane salt can effectively solve the problem of multi-boration of the product.The reaction does not require the use of any ligand,and it exhibits excellent regional specific selectivity for most non-terminal alkynes.The formation of regioisomers was found only in the hydroboration reactions of a few electron deficient terminal alkynes.The content of this paper is as follows:In the first chapter,the methods of building C-B keys are introduced;Progress in the Synthesis of Alkenyl Boron Compounds;Progress in Synthesis of boronate mono-triol boron salt;The topic and meaning of this paper.In the second chapter,boronate mono-triol boron saltwas synthesized;Five kinds of alkynes were synthesized by Sonogashira coupling;Synthesize four kinds of 1,3－alkynesby multi-step reactions.In the third chapter,theboronate mono-triol boron salt and 1-phenyl-1-propyne were used as reaction templates to determine the optimal reaction conditions by examining the reaction conditions.Afterwards,the adaptability of the substrate was investigated by the reaction of monoborane monoborane boron salt with aryl acetylenes and alkyl olefins.A total of 21 differently substituted alkenyl borate compounds were obtained.All known compounds were characterized by 1H NMR and the new compounds were characterized by 1H NMR,13C NMR and high resolution mass spectrometry.