Exploration of new synthetic methods for aromatic compounds based on the benzyne cycloaddition reactions

利用我们以前报道的苯炔区域选择性环加成反应得到的苯并环丁烯衍生物，发展了一些新的芳烃合成方法。(1)异色满-3-酮的新合成：在用芳香醛和四甲基哌啶锂处理后，苯并环丁烯酮经历其C（1）-C（4）键插入醛的羰基中，得到异色满-3-酮衍生物。该反应在温和的条件下进行，并且适用于苯并环丁烯酮和芳族醛的各种组合，从而能够合成在C（4）处具有烷基或烷氧基取代基的衍生物，这些衍生物难以通过迄今报道的方法合成。(2)2-烷氧基-2-乙烯基苯并环丁烯醇扩环为取代萘：在二烷基氨基锂的促进下，2-烷氧基-2-乙烯基苯并环丁烯醇衍生物通过在四元环的C（1）和C（2）位置之间引入两个乙烯基碳而进行扩环。反应有立体选择性地进行，立体化学过程为反应机理提供了新的视角。(3)联芳基化合物的新合成：芳基锂与2-烷氧基-2-乙烯基苯并环丁烯酮加成生成环丁烯醇盐，通过扩环得到芳基取代的二氢萘。产物在温和的酸处理下进行芳构化，得到相应的1-芳基萘。该方法适用于合成空间拥挤的联芳环衍生物。

Some new methods for aromatic synthesis have been developed by utilizing the benzocyclobutene derivatives obtained by the regioselective cycloaddition of benzyne which we previously reported.(1) Novel synthesis of isochroman-3-one :Upon treatment with an aromatic aldehyde and lithium tetramethylpiperidide, a benzocyclobutenone undergoes insertion of its C( 1 )-C(4) bond into the carbonyl of the aldehyde to give isochroman-3-one derivative. The reaction proceeds under mild conditions, and is applicable to various combinations of benzocyclobutenone and aromatic aldehyde, thereby enabling to synthesize the derivatives with an alkyl or an alkoxy substituent at the C(4) which were difficult to synthesize by the methods so far reported.(2) Ring expansion of 2-alkoxy-2-vinylbenzocyclobutenol into substituted naphthalene :Promoted by lithium dialkylamide, 2-alkoxy-2-vinylbenzocyclobutenol derivatives undergo ring expansion by incorporating the two vinyl carbons between the C(1) and C(2) positions of the fourmembered ring. The reaction proceeds stereoselectively, and the stereochemical courses give new views into the reaction mechanism.(3) Novel synthesis of biaryl compounds :The cyclobutenolate generated by addition of aryllithium to 2-alkoxy-2-vinylbenzocyclobutenone gives aryl-substituted dihydronaphthalene via the ring expansion. Aromatization of the product is effected under mild acid treatment to give the corresponding 1-arylnaphthalene. The method is valid for the synthesis of the derivatives which are sterically congested around the biaryl linkage.