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Asmic Isocyanide [3 + 2] Cascade to Dihydrooxazoles and Dihydroimidazoles.
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2020-07-08 , DOI: 10.1021/acs.joc.0c01119 Chepuri V Suneel Kumar 1 , Caleb W Holyoke 1 , Taylor M Keller 2 , Fraser F Fleming 1
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2020-07-08 , DOI: 10.1021/acs.joc.0c01119 Chepuri V Suneel Kumar 1 , Caleb W Holyoke 1 , Taylor M Keller 2 , Fraser F Fleming 1
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The versatile isocyanide building block Asmic, anisylsulfanylmethylisocyanide, reacts with aldehydes and ketones in a BF3·OEt2-mediated condensation to afford thioimidoyl-substituted 2,5-dihydrooxazoles. The condensation is distinguished from related base and transition-metal-catalyzed [3 + 2] processes in proceeding via the condensation of aldehydes and ketones with 2 equiv of an isocyanide followed by a molecular rearrangement that installs four new bonds. BF3·OEt2 mediates an analogous condensation of Asmic with imines to generate N-substituted dihydroimidazoles. Mechanistically, BF3·OEt2 activates the isocyanide to facilitate deprotonation evolving to a zwitterion that traps π-electrophiles in a formal [3 + 2] process. A second deprotonation–condensation with Asmic initiates a structural rearrangement involving a sulfanyl elimination–addition transposition sequence. The resulting dihydrooxazoles and dihydroimidazoles contain a thioimidate that serves as a diversification point for further elaboration.
中文翻译：
Asso Isocyanide [3 + 2]级联成二氢恶唑和二氢咪唑。
通用的异氰酸酯结构单元Asonic茴香基硫烷基甲基异氰化物在BF 3 ·OEt 2介导的缩合反应中与醛和酮反应，得到硫亚酰亚胺基取代的2,5-二氢恶唑。缩合与相关的碱和过渡金属催化的[3 + 2]过程不同，该过程通过醛和酮与2当量的异氰酸酯的缩合进行，然后进行分子重排，从而安装了四个新键。BF 3 ·OEt 2介导Asmic与亚胺的类似缩合，生成N取代的二氢咪唑。机械上，BF 3 ·OEt 2激活异氰酸酯以促进去质子化，演变成两性离子，从而在正式的[3 + 2]过程中俘获π-亲电子试剂。第二次去质子化（与Asmic缩合）引发涉及硫烷基消除-加成转座序列的结构重排。所得的二氢恶唑和二氢咪唑包含硫代亚氨酸酯，其用作进一步精制的分散点。
更新日期：2020-07-17
中文翻译：
Asso Isocyanide [3 + 2]级联成二氢恶唑和二氢咪唑。
通用的异氰酸酯结构单元Asonic茴香基硫烷基甲基异氰化物在BF 3 ·OEt 2介导的缩合反应中与醛和酮反应，得到硫亚酰亚胺基取代的2,5-二氢恶唑。缩合与相关的碱和过渡金属催化的[3 + 2]过程不同，该过程通过醛和酮与2当量的异氰酸酯的缩合进行，然后进行分子重排，从而安装了四个新键。BF 3 ·OEt 2介导Asmic与亚胺的类似缩合，生成N取代的二氢咪唑。机械上，BF 3 ·OEt 2激活异氰酸酯以促进去质子化，演变成两性离子，从而在正式的[3 + 2]过程中俘获π-亲电子试剂。第二次去质子化（与Asmic缩合）引发涉及硫烷基消除-加成转座序列的结构重排。所得的二氢恶唑和二氢咪唑包含硫代亚氨酸酯，其用作进一步精制的分散点。
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