Trifluoromethylated 2,3-dihydro-1,3,4-thiadiazoles via the regioselective [3+2]-cycloadditions of fluorinated nitrile imines with aryl, hetaryl, and ferrocenyl thioketones
A series of hydrazonoyl bromidespreparedfromreadily available N-arylhydrazones of fluoral was used for the in situ generation of fluorinated nitrile imines. These 1,3-dipoles were efficiently trapped with aryl and hetaryl thioketones yielding fluoromethylated 2,3-dihydro-1,3,4-thiadiazoles. The [3+2]-cycloadditions occurred with complete regioselectivity yielding the respective products in high
由易得的氟代N-芳基azo酮制备的一系列酰溴用于原位生成氟化腈亚胺。这些1,3-偶极有效地被芳基和杂芳基硫酮捕获,生成氟甲基化的2,3-二氢-1,3,4-噻二唑。[3 + 2]-环加成反应具有完全的区域选择性,从而以高收率产生了相应的产物。反应具有显着的耐受性进行到官能团,以及相应的Ñ(3)轴承卤素,甲氧基,苯甲酰氧基,甲氧羰基,和取代基腈在芳基衍生物对苯基环的位置被制备为结晶性产物。光谱数据(13 C和所获得的[3 + 2]-环加合物的19 F NMR)表明CF 3基团的屏蔽效应与对位取代基的电子性质之间存在显着的关系。
Hetero-Diels–Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles
Selected hetaryl and aryl thioketones react with acetylenecarboxylates under thermal conditions in the presence of LiClO4 or, alternatively, under high-pressure conditions (5 kbar) at room temperature yielding thiopyran derivatives. The hetero-Diels-Alder reaction occurs in a chemo- and regioselective manner. The initially formed [4 + 2] cycloadducts rearrange via a 1,3-hydrogen shift sequence to give