Asymmetric Synthesis using Hypervalent Iodine

1)二芳基1-λ^3-碘烷在温和的条件下将芳基转移到各种亲核试剂上，这可能是因为芳基碘基具有优异的离核性。然而，到目前为止，还没有合成出能够用于不对称合成的光学活性形式的这类有趣的二芳基1-λ^3-碘烷。本文首次报道了手性二芳基1-λ^3-碘烷、1，1 '-联萘-2-基（苯基）-λ^3-碘烷的合成、表征及其在β-酮酸酯衍生的烯醇阴离子的直接不对称α-苯基化反应中的应用。（二乙酰氧基碘）-1，1 '-联萘与四苯基锡烷在温和条件下发生锡-λ^3-碘烷交换反应，得到手性1，1'-联萘-2-基（苯基）- λ^3-碘烷。通过单晶X-射线衍射分析确定了手性λ^3-碘烷的结构和绝对构型，发现这些手性二芳基碘鎓盐发生了直接的不对称α-苯基化反应 ...更多信息 通过与具有40-50%对映体过量的环状β-酮酯的烯醇盐阴离子反应。手性2-碘-1，1 ′-联萘易于回收，不损失光学纯度，并可重复使用。分子内芳基自由基捕获实验表明碘（III）在此苯基化的配体耦合机制。我们认为这是第一个不需要使用过渡金属催化剂的金属烯醇化物的不对称苯基化反应。2）最近，我们报道了单羰基碘鎓叶立德的生成及其向醛的亚烷基转移反应，得到α，β-环氧酮。将Z-（2-乙酰氧基-1-癸烯基）-λ^3-碘烷暴露于EtOLi导致酯交换以生成单羰基碘鎓叶立德，同时释放乙酸乙酯。单羰基碘鎓叶立德作为羰基化合物的亚烷基转移剂，与醛在THF-DMSO中反应，主要生成E-异构体的α，β-环氧酮。含1，1 '-联萘基的手性单羰基碘鎓叶立德使高对映体过量的α，β-环氧酮的不对称合成成为可能。少

1) Diary1-λ^3-iodanes transfer the aryl group to a variety of nucleophiles under mild conditions, probably because of the excellent nucleofugality of the aryliodanyl group. To date, however, no members of this interesting class of diary1-λ^3-iodanes have been synthesized in an optically active form capable of being used in asymmetric synthesis. Reported here for the first time are the synthesis and characterization of the chiral diary1-λ^3-iodanes, 1, 1'-binaphthyl-2-yl(pheny1)-λ^3-iodanes, and their use in a direct asymmetric α-phenylation of enolate anions derived from cyclic β-keto esters.BF_3-Catalyzed reaction of 2-(diacetoxyiodo)-1, 1'-binaphthyl with tetraphenylstannane evoked tin-λ^3-iodane exchange under mild conditions and afforded chiral 1,1'-binaphthyl-2-yl(phenyl)- λ^3-iodanes. Structure and the absolute configuration of chiralλ^3-iodane were established by single-crystal X-ray analysis.These chiral diaryliodonium salts were found to undergo direct asymmetricα-phenylation … More by the reaction with enolate anions of cyclicβ-keto esters with 40-50% enantiomeric excess. The chiral 2-iodo-1 ,1'-binaphthyl was easily recovered, without loss of optical purity, and reused. Intramolecular aryl radical trapping experiments suggest a ligand-coupling mechanism on iodine(III) in this phenylation. We believe this is the first demonstration for asymmetric phenylation of metal enolates that does not require using a transition metal catalyst.2) Recently, we reported the generation of monocarbonyl iodonium ylides and their alkylidene transfer reactions to aldehydes yielding α, β-epoxy ketones. Exposure of Z-(2-acetoxy-1-decenyl)-λ^3-iodanes to EtOLi results in ester exchange to generate the monocarbonyl iodonium ylide with the liberation of ethyl acetate. The monocarbonyl iodonium ylide acts as an alkylidene transfer agent to carbonyl compounds, and the reaction with aldehydes in THF-DMSO gives α, β-epoxy ketones with E-isomers as a major product. Chiral monocarbonyl iodonium ylides with 1, 1'-binaphthyl groups make possible asymmetric synthesis of α, β-epoxy ketones with high enantiomeric excess. Less