Hexacarbonylmolybdenum(0)-Induced Dechalcogenization of Allylic Sulfides, Sulfones, and Selenides: Nucleophilic Substitution and Reductive Dechalcogenization
Hexacarbonylmolybdenum(0)-induced dechalcogenization of allylic sulfides I, sulfones II, and selenides III in refluxing dioxane, which led to nucleophilic substitutions with carbon nucleophiles. Attack of the relatively bulky nucleophile, 2-ethoxycarbonyl-2-sodiocyclopentanone occurred regioselectively at the less substituted end of the allyl unit after the dechalcogenization to give only one isomer
六羰基钼 (0) 诱导的烯丙基硫化物 I、砜 II 和硒化物 III 在回流的二恶烷中脱硫,导致碳亲核试剂发生亲核取代。相对庞大的亲核试剂 2-乙氧羰基-2-钠基环戊酮的攻击在脱硫后烯丙基单元的较少取代末端发生区域选择性,仅产生一种异构体。钠丙二酸二乙酯对 I 和 III 的攻击优先发生在 γ 位,而对 II 的攻击优先发生在脱磺酰化后烯丙基单元的更多取代端。在没有碳亲核试剂的情况下,在回流的二恶烷中用 Mo(CO)6 处理 I、II 和 III 导致还原性脱硫。H2O 的加入加速了还原脱硫。
The Magnesium−Ene Cyclization Stereochemically Directed by an Allylic Oxyanionic Group and Its Application to a Highly Stereoselective Synthesis of (±)-Matatabiether. Allylmagnesium Compounds by Reductive Magnesiation of Allyl Phenyl Sulfides<sup>1</sup>
more easily prepared in a connective fashion than the usual allyl halide precursor. Since the presence of lithium ions encourages undesirable proton transfer to the cyclized organometallic and is detrimental to the stereochemical control, the conversion of the allylic thioether to the allylmagnesium utilizes a lithium-free method involving direct reductive magnesiation in the presence of the magnesium-anthracene
[3-(Ethylthio)allyl]titanium reagent generated easily from allyl ethyl sulfides condensed with aldehydes to give erythro-β-hydroxy sulfides in highly regio- and stereoselective manner. In contrast, crotyl ethyl sulfide reacted with aldehydes affording δ-hydroxy vinyl sulfide exclusively. The substitution pattern of the starting sulfide can have a pronounced effect on the selectivity in this condensation reaction