Borono-catellani Ortho Alkylation/ipso Alkynylation And Asymmetric Total Synthesis Of Solanone And Its Three Isomers

In 1997,Prof.Catellani,an Italian scientist,developed a method of synergistic catalysis of palladium and norborneene,which can achieve both ortho and ipso positions bifunctionalization of aryl halides.In the past two decades,the reaction has achieved many landmark research advances,becoming a widely used synthesis strategy.In traditional Catellani reactions,the substrates are usually aryl halides initiated by unstable Pd(0).However,recent studies have shown that Catellani reaction can also be initiated by Pd(II)catalyst,and can be divided into indoles and pyrrole compounds,aromatic compounds with directing groups,and aryl boronic acids and their derivatives according to the substrate types.The first part of this paper focuses on the Catellani reaction in which aryl borates are involved,and the following results are obtained: the ortho alkylation/ipso alkynylation of aryl borates has been successfully achieved.This reaction has the advantages of cheap raw materials,no phosphine ligands,air as oxidant,simple operation,reaction at room temperature,wide application range of substrates,good functional group compatibility and so on.Solanone plays an important role in the aroma of tobacco and the cigarette industry has a great demand for solanone and its related aroma substances.However,the content of solanone in tobacco is very low,to meet this demand,synthetic methods can be achieved.Although more than ten kinds of synthetic routes of solanone have been reported at home and abroad,the following problems still exist:(1)the synthesis routes are long,inefficient and uneconomical;(2)A large number of alkyl metal reagents are used,the operation is difficult and safety is difficult to ensure;(3)The synthesis of solanone was mainly focused on the synthesis of solanone racemate,while the synthesis of solanone monomer was rare.The second part of this paper focuses on the synthesis of solanone and its three isomers: the preparation of optically pure solanone(5S,6E)-solanone and its enantiomer solanone(5R,6E)-solanone in grams by only two steps,using cheap raw materials,asymmetric Michael addition reaction catalyzed by organic small molecules and Horner-Wadsworth-Emmons reaction as key steps.The preparation of optically pure solanone(5S,6Z)-solanone and its enantiomer solanone(5R,6Z)-solanone was accomplished by only three steps of transformation using cheap raw materials,asymmetric Michael addition reaction catalyzed by organic small molecules,Wittig reaction and Suzuki coupling reaction as the key steps.The total yield of the four configurations was 41%,40%,37%,35% and enantiomeric excess was 88%,90%,91%,94%,respectively.This route has the advantages of short steps,cheap raw materials,safe reagents,simple operation and so on,and has realized the highefficiency asymmetric synthesis of solanone and its three isomers,which is of great significance to the in-depth exploration of the value of this kind of spices and the development of green industrialization technology.