Asymmetric Synthesis using Hypervalent Iodine

1)二芳基1-λ^3-碘在温和的条件下将芳基转移到多种亲核试剂上，这可能是因为芳基具有良好的亲核性。然而，到目前为止，这类有趣的1-λ^3-碘烷还没有以光学活性的形式合成，能够用于不对称合成。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-碘烷的合成和表征，以及它们在直接不对称α-苯基化反应中的应用。BF_3催化的2-(二乙酰氧基碘)-1，1’-联萘与四苯基锡烷的反应在温和的条件下引发了锡-β^3-碘的交换，得到了手性的1，1‘-联萘-2-基(苯基)-λ^3-碘。通过单晶X-射线分析确定了手性λ的结构和绝对构型，发现这些手性二芳碘盐发生了直接的不对称α-苯基化…反应更多的是通过与具有40-50%对映体过剩的环状β-酮酸酯的烯酸阴离子反应。手性2-碘-1，1‘-联萘易于回收，不损失光学纯度，可重复使用。分子内芳基自由基捕捉实验表明，在苯基化反应中，碘(III)存在配体偶联机制。我们相信这是第一个不需要使用过渡金属催化剂的金属烯醇酸盐不对称苯基化的证明。2)最近，我们报道了单羰基碘叶立德的生成及其与醛的亚烷基转移反应，生成了α，β-环氧酮。Z-(2-乙酰氧基-1-癸烯基)-λ^3-碘烷与乙酸乙酯反应，在乙酸乙酯释放的同时，发生酯交换反应，生成单甲酰基碘叶立德。单甲基碘叶立德作为烷叉转移剂，在四氢呋喃-二甲基亚砜中与醛反应生成以E-异构体为主的α，β-环氧酮。含1，1‘-联萘基的手性单羰基碘叶立德使高对映体过剩的α，β-环氧酮的不对称合成成为可能。较少

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